
Class, 1 , Y\ \ 5 \ 
Book JHJL- 



Electrical Engineer's 
pocket-book: 









A HAND-BOOK 

OF USEFUL DATA FOE ELECTRICIANS AND 

ELECTRICAL ENGINEERS. 



BY • « 

HOEATIO A. FOSTER. 

Mem. A. I. ~&, j£g; Mem.. A, "§. >1. j$' > - ; 
Consulting Engineer. 



WITH THE COLLABORATION OF EMINENT 
SPECIALISTS. 

THIRD EDITION, CORRECTED. 
NINTH THOUSAND. 




NEW YORK: 

D. VAN NOSTRAND COMPANY 

LONDON : 

E. & F. N. SPON, Ltd. 
1903 



M 



i 






COPYRIGHT, 1901, 1902, BY 

D. VAN NOSTRAND COMPANY. 






TYPOGRAPHY BY C. J. PETERS & SON. 



PRESSWORK AND BINDING BY F. H. GILSON OO. 
BOSTON, MASS., V. S. A. 



ILLUSTRATIONS BY BORMAY & CO., NEW YORK. 



PREFACE. 



It is with some little trepidation that this book is put 
before the public, in view of the frequent important, and 
even radical, changes that up to the present have char- 
acterized the development of electrical engineering. It 
has, however, been thought that the science has now 
reached a stage which renders necessary some manual 
that will be of assistance to the active worker in the 
various branches. 

This book is not an encyclopedia, nor is it intended 
for a text-book, but it is hoped that as a compendium of 
useful data it may assist the practicing electrician and 
engineer. 

The matter included is representative of American 
practice, and no effort has been made to include any 
other, except in special cases. No excuse is offered for 
the very considerable amount of matter taken from 
trade publications of the larger electrical manufacturers, 
as in this country the engineers retained by such works 
are specialists — often the best in their various 
branches ; and it is an accident of condition only that in 
some cases has compelled the use of more of the publi- 
cations of one company than of another, based upon 
available published material. 

Manufacturers have been most kind in supplying any 
special data and descriptions asked for ; and the author's 
thanks are in particular due to a large circle of asso- 



IV PREFACE. 

ciates for suggestions, revisions, critical proof-reading, 
and the various other details involved in a compilation 
of this kind, of whom the following deserve especial 
mention for valuable aid rendered : Messrs. F. E. IdelL, 
W. D. Weaver, T. C. Martin, Prof. Samuel Sheldon, 
E. B. Raymond, John S. Griggs, Jr., William Wallace 
Christie, J. J. Crain, Grahame H. Powell, Prof. Francis 
B. Crocker, A. K Mansfield, E. M. Hewlett, C. F. Scott, 
H. S. Putnam, Charles Henry Davis, Townsend Wolcott, 
Walter S. Moody, Herbert Laws Webb, Charles Thorn, 
William Maver, Jr., Joseph Appleton, Prof. Alex. G-. 
McAdie, Thorburn Reid, Max Osterberg, Max Loewen- 
thal, J. G-. White & Co. The especial thanks of the 
author are due to the indefatigable co-operation of Mr. 
Charles E. Speirs, of the D. Van Nostrand Co., who 
has rendered most valuable assistance in properly get- 
ting the matter into shape for publication. 

In closing, the author begs that readers will not hesi- 
tate to point out errors found in the text or tables, as 
many will doubtless crop out in the close examination 
by numerous readers. 

HORATIO A. FOSTER. 
650 Bullitt Building, 

Philadelphia, 
1901. 



LIST OF CONTRIBUTORS. 



SECTION. 

Symbols, Units and Instruments. 
Resistance, Electrical Measurements. 
Cable Testing (re-written). 
Conductors (Properties of). 
Conductors (Relation and Dimension of). 
Electric Lighting. 
Lightning Arresters. 

Electric Street Railways. 

Storage Batteries. 

Telephony. 

Magnetic Properties of Iron. 

Electromagnets. 

Determination of Wave Form. 

Electricity Meters. 

Dynamos and Motors. 

Dynamos and Motors Standard and Test. 

Static Transformers. 

Telegraphy. 

Switchboards and Switching Devices. 
Transmission of Power. 
Certain Uses of Electricity in U. S. Army. 
Electricity in U. S. Navy. 
Electro-chemistry, Electro-metallurgy. 
Electric Heating, Cooking, and Electric 
"Welding. 

Mechanical Section. 

Lightning Conductors. 
Miscellaneous Section. 
Underwriters' Code. 
Index Electrical Section. 
Index Mechanical Section. 



REVISED BY 

Prof. Samuel Sheldon. 

Prof. Samuel Sheldon. 

Mr. William Maver, Jr. 

Prof. Samuel Sheldon. 

Prof. Samuel Sheldon. 

Mr. Townsend Wolcott. 

Mr. Townsend Wolcott. 
f Mr. John S. Griggs, Jr. 
I J. G. White & Co. 

Mr. Townsend Wolcott. 

Mr. Herbert Laws Webb. 

Prof. Samuel Sheldon. 

Mr. Townsend Wolcott. 
\ Mr. Townsend Wolcott. 
I Louis Robinson. 

Prof. Samuel Sheldon. 

Mr. E. B. Raymond. 

Mr. E. B. Raymond. 
( Mr. Walter S. Moody. 
I Mr. Townsend Wolcott. 
( Mr. Chas. Thorn. 
I Mr. Herbert Laws Webb. 

Mr. E. M. Hewlett. 

Mr. T. C. Martin. 

Mr. Grahame H. Powell. 

Mr. J. J. Crain. 

Prof. Francis B. Crocker. 
( Mr. Max Osterberg. 
I Mr. Max Loewenthal. 
( Mr. Wm. Wallace Christie. 
I Mr. F. E. Idell. 

Prof. Alex. G. McAdie. 

Mr. Townsend Wolcott. 

Mr. Max Loewenthal. 
Mr. Wm. Wallace Christie. 



CONTENTS. 



PAGE 

Symbols, Units, Instruments 1 

Resistance Measurements 38 

Magnetic Properties of Iron 64 

Electro-magnets 81 

Relation and Dimensions of Conductors 92 

Properties of Conductors 140 

Cable Testing 220 

Dynamos and Motors 230 

Dynamo and Motor Standards „ 293 

The Static Transformer 331 

Electric Lighting 386 

Electric Street Railways 423 

Transmission of Power 548 

Storage Batteries 552 

Switchboards 585 

Lightning Arresters 601 

Electricity Meters 615 

Telegraphy 636 

Telephony 645 

Electro-Chemistry and Electro-Metallurgy 675 

Electric Heating, Cooking, and Welding 683 

Operation of Electric Mining Plants 696 

Lightning Conductors 701 

Determination of Wave Eorm 705 

Electricity in the IT. S. Army 711 

Electricity in the U. S. Navy 727 

Miscellaneous 757 

National Code Rules and Requirements 762 

Mechanical Section 791 

Index 977 



SYMBOLS, UNITS, INSTRUMENTS. 



CHAPTER I. 



EIEC1HICAI EI«I1VEEBII& §¥MBOLS. 

The following list of symbols has been compiled from various sources as 
being those most commonly in use in the United States. Little variation 
will be found from similar lists already published except the elimination of 
some that may be considered exclusively foreign. The list has been revised 
by competent authorities and may be considered as representing the best 
usage. 



fundamental. 



h 


Length, cm. = centimeter ; 




in., or // =inch, ft. or ' = 




foot. 


M, 


Mass. gr. = mass of 1 




gramme ; kg. = 1 kilo- 




gramme. 


T, t, 


Time. s = second. 




Derived: geometric. 


S, s, 


Surface. 


V, 


Volume. 


o,j8, 


Angle. 




Mechanical. 


v, 


Velocity. 


m, 


Momentum. 


bif 


Angular velocity. 


a, 


Acceleration. 


9, 


Acceleration due to gravity 




= 32.2 feet per second. 


F,f, 


Force. 


W, 


Work. 



P, Power. 

5, Dyne, 10 S = 10 dynes. 

e, Ergs. 

ft. lb., Foot-pound. 

H.p. , h.p. ; IP, Horse-power. 

I.H.P., Indicated horse-power. 

B.H.P., Brake horse-power. 

E.H. P., Electrical horse-power. 

J, Joules' equivalent. 

Pi Pressure. 

K, Moment of inertia. 

Derived Electrostatic. 

q, Quantity. 

i, Current. 

e, Potential Difference. 

r, Resistance. 

k, Capacity. 

sk, Specific Inductive capacity. 

Derived Magnetic. 

m, Strength of pole. 

6)j£ Magnetic moment. 



3, 

oe, 

eft. 



Intensity of magnetization. 



Horizontal intensity of 
earth's magnetism. 

Field intensity. 

Magnetic Flux. 

Magnetic flux density or 
magnetic induction. 

Magnetizing force. 

Magnetomotive force. 

Reluctance, Magnetic re- 
sistance. 
, Magnetic permeability. 

Magnetic susceptibility. 

Reluctivity (specific mag- 
netic resistance). 

Derived electroiiiag-netic. 



/?, Resistance, Ohm. 

n, do, megohm. 

E, Electromotive force, volt. 

U, Difference of potential, volt. 

/, Intensity of current, Ampere. 

Q, Quantity of electricity, Am- 

pere-hour ; Coulomb. 

C, Capacity. Farad. 

W, Electric Energy, Watt-hour ; 

Joule. 

P, Electric Power, Watt ; Kilo- 

watt. 

p, Resistivity (specific resis- 

tance), Ohm-centimeter. 

G, Conductance, Mho. 

y, Conductivity (specific con- 

ductivity. 

L, Inductance (coefficient of 

Induction), Henry. 

v, Ratio of electro-magnetic to 

electrostatic unit of quan- 
tity =3 x 10 10 centimeters 
per second approximately. 

Symbols in g-eneral use. 

D, Diameter. 
r, Radius. 

t. Temperature. 

9, Deflection of galvanometer 

needle. 



SYMBOLS, UNITS, INSTRUMENTS. 



jY, n, Number of anything. 

ir, Circumference — diameter : 

3.141592. 
w, 2 ttN = 6.2831 X frequency, in 

alternating current. 
e> Frequency, periodicity 

cles per second. 
G, Galvanometer. 

S, Shunt. 

N, n, North pole of a magnet. 
S, 8, South pole of a magnet. 
A.M. Ammeter. 
V.M. Voltmeter. 
A.C. Alternating current. 
D.C. Direct current. 
P.D. Potential difference. 
C.G.S. Centimeter, Gramme, Second 

system. 
B. & S. Brown & Sharpe wire gauge. 
B.W.G., Birmingham Wire gauge. 




Revolutions per minute. 
Candlepower. 
Incandescent lamp. 

Arc lamp. 

Condenser. 

Battery of cells. 

Dynamo or motor, d.c. 

Dynamo or motor, a.c. 

Converter. 

Static transformer. 

Inductive resistance. 
Non-inductive resistance. 



CHAPTER II. 

ELECTRICAL EA'GOEERl.^ UNITS. 

Index Notation. 

Electrical units and values oftentimes require the use of large numbers 
of many figures both as whole numbers and in decimals. In order to avoid 
this to a great extent the index method of notation is in universal use in 
connection with all electrical computations. 

In indicating a large number, for example, say, a million, instead of writ- 
ing 1,000,000, it would by the index method be written 10« ■ and 35 000 00(1 
would be written 35 x 10". ' ' 

A decimal is written with a minus sign before the exponent, or, -i„ — 01 
r= 10" 2 ; and .00048 is written 48 x 10~ 5 . . ~ 

The velocity of light is 30,000,000,000 cms. per sec, and is written 3 x 10". 

In multiplying numbers expressed in this notation the significant figures 
are multiplied, and to their product is annexed 10, with an index equal to 
the sum of the indices of the two numbers. 

* « di Y?£ n g< the significant figures are divided, and 10, with an index equal 
to the difference of the two indices of the numbers is annexed to the divi- 
dend. 

Fundamental Units. 

The physical qualities, such as force, velocity, momentum, etc., are ex- 
pressed in terms of length, m,ass, time, and for electricity the system of 
terms in universal use is that known as the C. G. S. system, 
viz. : — The unit of length is the Centimeter. 

The unit of mass is the Gramme. 
The unit of time is the Second. 

Expressed in more familiar units, the Centimeter is equal to .3937 inch in 
length ; the Gramme is equal to 15.432 grains, and represents the mass or 
quantity of a cubic centimeter of water at 4° C, or 39.2° Fah. ; the Second is 
th e SBig?.?ra P art of a sidereal day, or the 5B ^j5 5 part of a mean solar day. 

These units are also often called absolute units. 

Derived Oeometric Units. 

The unit of area or surface is the square centimeter. 
The unit of volume is the cubic centimeter. 



Derived Mechanical Units. 

Velocity is the rate of change of position, and is uniform velocity when 
equal distances are passed over in equal spaces of time ; unit velocity is a 
rate of change of one centimeter per second. 



ELECTRICAL ENGINEERING UNITS. 



Angular Velocity is the angular distance about a center passed through in 
one second of time. Unit angular velocity is the velocity of a body moving 
in a circular path, whose radius is unity, and which would traverse a unit 
angle in unit time. Unit angle is 57°, 17', 44. 8" approximately ; i.e., an angle 
whose arc equals its radius. 

Momentum is the quantity of motion in a body, and equals the mass times 
the velocity. 

Acceleration is the rate at which velocity changes ; the unit is an accel- 
eration of one centimeter per second per second. The acceleration due to 
gravity is the increment in velocity imparted to falling bodies by gravity, 
and is usually taken as 32.2 feet per second, or 981 centimeters per second. 
This value differs somewhat at different localities. At the North Pole g = 
983.1 ; at the equator g = 978.1 ; and at Greenwich it is 981.1. 

Force acts to change a body's condition of rest or motion. It is that which 
tends to produce, alter, or destroy motion, and is measured by the change 
of momentum produced. 

The unit of force is that force which, acting for one second on a mass of 
one gramme, gives the mass a velocity of one centimeter per second ; this 
unit is called a dyne. The force of gravity or weight of a mass in dynes may 
be found by multiplying the mass in grammes by the value of g at the par- 
ticular place where the force is exerted. The pull of gravity on one pound 
in the United States may be taken as 445,000 dynes. 

Work is the product of a force into the distance through which it acts. 
The unit is the erg, and equals the work done in pushing a mass through a 
distance of one centimeter against a force of one dyne. As the " weight " 
of one gramme is 1 X 981, or 981 dynes, the work done in raising a weight of 
one gramme through a height of one centimeter against the force of gravity, 
or 981 dynes, equals 1 X 981 = 981 ergs. 

One kilogramme- meter = 100000 x 981 ergs. 

Kinetic energy is the work a body is able to do by reason of its motion. 

Potential energy is the work a body is able to do by reason of its position. 

The unit of energy is the erg. 

Power is the rate of working, and the unit is the watt=10 7 ergs per sec. 
Horse-power is the unit of power in common use and, although a somewhat 
arbitrary unit, it is difficult to compel people to change from it to any other. 
It equals 33,000 lbs. raised one foot high in one minute, or 550 foot-pounds 
per second. 

1 f t.-lb. = 1.356 x 10 7 ergs. 

1 watt = 10 7 ergs per second. 

i horse-power = 550 x 1.356 x 10 7 ergs = 746 watts. If a current of / am- 
peres flow through R ohms under a pressure of E volts, then — = = 

i 46 74b 

E 2 
— — represents the horse-power involved. 

The French "force de cheval" =736 watts = 542.48 ft. lbs. per sec.= 
.9863 H. P., and 1 H.P. = 1.01389 "force de cheval." 

Heat. The Joule WJ— 10 7 ergs, and is the work done, or heat generated, by 
a watt second, or ampere flowing for a second through a resistance of an ohm. 
If # = heat generated in gramme calories, 
i = current in amperes, 
_E=e.m.f. in volts, 
R = resistance in ohms, and 
t = time in seconds, 
then J?— :0.24i" 2 ift=0.24 EH. gramme calories or therms. 

EH 
Then IEt = I 2 Rt= — = EQ= Joules. 



or, as 1 horse 



s-power = 550 foot-pounds of work per second, 
Joules = f |§ E Q = .7373 E Q f t. lbs . 

Heat Units. 

The British Thermal Unit is the amount of heat required to raise the 
temperature of one pound of water from 60° F. to 61°, = 1 pound-degree- 
Fah. = 251.9 French units. 

The therm, or French calorie, is the amount of heat required to raise the 



SYMBOLS, UNITS, INSTRUMENTS. 



temperature of a mass of 1 gramme of water from 4° C. to 5° C. = 1 gramme- 
degree-centigrade. 

Water at 4° 0. is at its maximum density. 

Joules equivalent, J, is the amount of energy equal to a heat unit. 

For a B.T.U., or pound-degree-Fah., J = 1.07 X 10 10 ergs., or = 778 foot- 
pounds. 

For one pound-degree — Centigrade, J = 1.93 X 10 10 ergs. 

For a calorie .7=4.189 X 10 7 ergs. 

The heat generated in t seconds of time is 

I -^- = ~ , where ,7=4.189 X 10 7 , 

and I, R, and E are expressed in practical units. 

Electrical Units. 

There are two sets of electrical units derived from the fundamental 
C. G. S. units; viz., the electrostatic and the electromagnetic. The first is 
based on the force exerted between two quantities of electricity, and the sec- 
ond upon the force exerted between a current and a magnetic pole. The 
ratio of the electrostatic to the electromagnetic units has been carefully de- 
termined by a number of authorities, and is found to be some multiple or 
sub-multiple of a quantity represented by v., whose value is approximately 
3 x 10 10 centimeters per second. Convenient rules for changing from one to 
the other set of units will be stated later on in this chapter. 

Electrostatic Units. 

As yet there have been no names assigned to these. Their values are as 
follows : — 

The unit of quantity is that quantity of electricity which repels with a 
force of one dyne a similar and equal quantity of electricity placed at unit 
distance (one centimeter) in air. 

Unit of current is that which conveys a unit of quantity along a conduc- 
tor in unit time (one second). 

Unit difference of potential or unit electro-motive force exists between two 
points when one erg of work is required to pass a unit quantity of electricity 
from one point to the other. 

Unit of resistance is possessed by that conductor through which unit cur- 
rent will pass under Unit electro-motive force at its ends. 

Unit of capacity is that which, when charged by unit potential, will hold 
one unit of electricity ; or that capacity which, when charged with one unit 
of electricity, has a unit difference of potential. 

Specific inductive capacity of a substance is the ratio between the capacity 
of a condenser having that substance as a dielectric to the capacity of the 
same condenser using dry air at 0° C. and a pressure of 76 centimeters as 
the dielectric. 

Mag-netic Units. 

Unit Strength of Pole (symbol m) is that which repels another similar and 
equal pole with unit force (one dyne) when placed at unit distance (one 
centimeter) from it. 

Magnetic Moment (symbol 9TC) is the product of the strength of either 
pole into the distance between the two poles. 

Intensity of Magnetization is the magnetic moment of a magnet divided 
by its volume, (symbol 3)- 

Intensity of Magnetic Field (symbol 0£ ) is measured by the force it exerts 
upon a unit magnetic pole, and therefore the unit is that intensity of held 
which acts on a unit pole with a unit force (one dyne). 

Magnetic Induction (symbol (&) is the magnetic flux or the number of 
magnetic lines per unit area of cross-section of magnetized material, the 
area being at every point perpendicular to the direction of flux. It is equal 
to the magnetizing force or field intensity J£ multiplied by the permeability 
fx.: the unit is the gauss. 

Magnetic Flux (symbol <I>)is equal to the average field intensity multiplied 
by the area. Its unit is the maxwell. 

Magnetizing Force (symbol J£ ) per unit of length of a solenoid equals 



ELECTRICAL ENGINEERING UNITS. 



4 n NI-±- L where N= the number of turns of wire on the solenoid ; L =: 
the length of the solenoid in cms., and /= the current in absolute units. 

Magnetomotive Force (symbol £p ) is the total magnetizing force developed 
in a magnetic circuit by a coil, equals 4 n NI, and the unit is the gil- 
bert. 

Reluctance, or Magnetic Resistance (symbol (${), is the resistance offered to 
the magnetic flux by the material magnetized, and is the ratio of magneto- 
motive force to magnetic flux; that is, unit magnetomotive force will generate 
a unit of magnetic flux through unit reluctance : the unit is the oersted; i.e., 
the reluctance offered by a cubic centimeter of vacuum. 

Magnetic Permeability (symbol /u) is the ratio of the magnetic induction 

(ft to the magnetizing force J£, that is -^ = /x. 

Magnetic Susceptibility (symbol k) is the ratio of the intensity of mag- 
netization to the magnetizing force, or/< = ^ • 

Reluctivity , or Specific Magnetic Resistance (symbol v), is the reluctance 
per unit of length and of unit cross-section that a material offers to being 
magnetized. 

Electromagnetic Units. 

Resistance (symbol R) is that property of a material that opposes the flow 
of a current of electricity through it; and the unit is that resistance which, 
with an electro-motive force or pressure between its ends of one unit, will 
permit the flow of a unit of current. 

The practical unit is the ohm, and its value in C.S.G. units is 10 9 . The 
standard unit is a column of pure mercury at 0° C, of uniform cross-section, 
106.3 centimeters long, and 14.4521 grammes weight. For convenience in use 
for very high resistances the prefix meg is used; and the megohm, or million 
ohms, becomes the unit for use in expressing the insulation resistances of 
submarine cables and all other high resistances. 

Electro-motive Force (symbol E) is the electric pressure which forces the 
current through a resistance, and unit E.M.F. is that pressure which will 
force a unit current one ampere through a unit resistance. The unit is the 
volt, and the practical standard adopted by the international congress of elec- 
tricians at Chicago in 1893 is the Clark cell, directions for making which 
will be given farther on. The E.M.F. of a Clark cell is 1.434 volt at 15° C. 

The value of the volt in C.G.S. units is 10 8 . For small E.M.F's. the unit 
millivolt, or one-thousandth volt, is used. 

Difference of Potential, as the name indicates, is simply a difference of 
electric pressure between two points. The unit is the volt. 

Current (symbol /) is the intensity of the electric current that flows 
through a circuit. A unit current will flow through a resistance of one 
ohm, with an electro-motive force of one volt between its ends. The unit 
is the ampere, and is practically represented by the current that will electro- 
lytically deposit silver at the rate of .001118 gramme per second. Its value 
in C.G.S. units is 10 _ 1 . For small values the milliampere is used, and it 
equals one-thousandth of an ampere. 

The Quantity of Electricity (symbol Q) which passes through a given cross- 
section of an individual circuit in t seconds when a current of / amperes is 
flowing is equal to It units. The unit is therefore the ampere-second. Its 
name is the Coulomb, and its value in C.G.S. units is 10 _1 . 

Capacity (symbol C) is the property of a material condenser for holding 
a charge of electricity. A condenser of unit capacity is one which will be 
charged to a potential of one volt by a quantity of 1 coulomb. The unit is 
the farad, its C.G.S. value is 10~ 9 ; and this being so much larger than ever 
obtains in practical work, its millionth part, or the micro-farad, is used as 
the practical unit, and its value in absolute units is 10 _15 .' A condenser of 
one-third micro-farad capacity is the size in most common use in the United 
States. 

Electric Energy (symbol W) is represented by the work done in a circuit 
or conductor by a current flowing through it. The unit is the Joule, its 
absolute value is 10 7 ergs, and it reprepresents the work done by the flow 
for one second of unit current (1 ampere) through 1 ohm. 

Electric Power (symbol P) is measured in watts, and is represented by a 
current of 1 ampere under a pressure of 1 volt, or 1 Joule per second. The 



SYMBOLS, UNITS, INSTRUMENTS. 



> ° 



£* 






£ . 

>- 3 
to .2 

S. |_| 



SES M 









£ m 

a o 



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ELECTRICAL ENGINEERING UNITS. 









si 

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e h e e ^ c ^ 

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Dyne per sc 

centime^ 

Granune-mas 

timeter-squj 










Gauss. 

Maxwel 

Gauss. 

Gauss. 

Gilbert 

Oersted 











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H« WIN _ 

£ ^ ^ 

MUM 10IC1 1 

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^ ^ ^ ^ S! N 

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Kl^ ^1 K] ^ 


s 
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II II II 

a, s< & 


*ll II 

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P3 « S 



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V +a -w .~ 



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SYMBOLS, UNITS, INSTRUMENTS. 



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fe 


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Abbre 

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the 

Practii 

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ft 


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W 














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to 

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CD 

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d 










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INTERNATIONAL ELECTRICAL UNITS. 



watt equals 10 7 absolute units, and 746 watts equals 1 horse-power. In elec- 
tric lighting and power the unit kilowatt, or 1000 watts, is considerably used 
to avoid the use of large numbers. 

Resistivity (symbol p) is the specific resistance of a substance, and is the 
resistance in ohms of a centimeter cube of the material to a flow of cur- 
rent between opposite faces. 

Conductance (symbol 6?) is that property of a metal or substance by which 
it conducts an electric current, and equals the reciprocal of its resistance. 
The unit proposed for conductance is the Mho, but it has not come into 
prominent use as yet. 

Conductivity (symbol v) is the specific conductance of a material, and is 
therefore the reciprocal of its resistivity. It is often expressed in compari- 
son with the conductivity of some standard metal such as silver or copper, 
and is then stated as a percentage. 

Inductance (symbol L), or coefficient of self-induction, of a circuit is that 
coefficient by which the time rate of change of the current in the circuit 
must be multiplied in order to give the E.M.F. of self-induction in the 
circuit. The practical unit is the henry, which equals 10 9 absolute units, 
and exists in a circuit when a current varying 1 ampere per second produces 
a volt of electro-motive force in that circuit. As the henry is so large as to 
be seldom met with in practice, 1 thousandth of it, or the milli-henry, is the 
unit most in use. 

Below will be found a few rules for reducing values stated in electrostatic 
units to units in the electro-magnetic system. To reduce 

electrostatic potential to volts, multiply by 300 ; 

" capacity to micro-farads, divide by 900,000 ; 

" quantity to coulombs, divide by 3 x 10 9 ; 

" current to amperes, divide by 3 x 10 9 ; 

" resistance to ohms, multiply by 9 X 10 u . 

IHTERUATIOISAL ELECTRICAI XTWITS. 
At the International Congress of Electricians, held at Chicago, August 21, 
•1893, the following resolutions met with unanimous approval, and being 
approved for publication by the Treasury Department of the United States 
Government, Dec. 27, 1893, and legalized by act of Congress and approved 
by the President, July 12, 1894, are now recognized as the International 
units of value for their respective purposes. 

RESOL VET), That the several governments represented by the delegates 
of the International Congress of Electricians be, and they are hereby, 
recommended to formally adopt as legal units of electrical measure the 
f ollowing : — 

1. As a unit of resistance, the International ohm, which is based upon the 
ohm equal to 10 9 units of resistance of the C.G.S. system of electro-magnetic 
units, and is represented by the resistance offered to an unvarying electric 
current by a column of mercury at a temperature of melting ice, 14.4521 
grammes in mass, of a constant cross-sectional area, and of the length 106.3 
centimeters. 

2. As a unit of current, the International ampere, which is one-tenth of the 
unit of current of the C.G.S. system of electro-magnetic units, and which is 
represented sufficiently well for practical use by the unvarying current 
which, when passed through a solution of nitrate of silver in water, in 
accordance with the accompanying specification (A) deposits silver at the 
rate of 0.001118 gramme per second. 

3. As a unit of electro-motive force the international volt which is the 
E.M.F. that, steadily applied to a conductor whose resistance is one Inter- 
national ohm, will produce a current of one international ampere, and 

which is represented sufficiently well for practical use by — — of the E.M.F. 

between the poles or electrodes of the voltaic cell known as Clark's cell at 
a temperature of 15° C, and prepared in the manner described in the ac- 
companying specification (B). 

4. As the unit of quantity, the International coulomb, which is the quan- 
tity of electricity transferred by a current of one international ampere in 
one second. 

5. As the unit of capacity the international farad, which is the capacity 



10 SYMBOLS, UNITS, INSTRUMENTS. 

of a conductor charged to a, potential of one international volt by one inter- 
national coulomb of electricity. 

6. As the unit of work, the joule, which is 10 7 units of work in the C.G.S. 
system, and which is represented sufficiently well for practical use by the 
energy expended in one second by an international ampere in an inter- 
national ohm. 

7. As the unit of poiver, the watt, which is equal to 10 7 units of power in the 
C.G.S. system, and Avhich is represented sufficiently well for practical use 
by the work done at the rate of one joule per second. 

8. As the unit of induction, the henry, which is the induction in the cir- 
cuit when the E.M.F. induced in this circuit is one international volt, while 
the inducing current varies at the rate of one international ampere per 
second 

Specification A. 

In employing the silver voltameter to measure currents of about one 
ampere, the following arrangements shall be adopted : 

The kathode on which the silver is to be deposited shall take the form of 
a platinum bowl not less than 10 cms. in diameter, and from 4 to 5 cms. in 
depth. 

The anode shall be a disk or plate of pure silver some 30 sq. cms. in area, 
and 2 or 3 cms. in thickness. 

This shall be supported horizontally in the liquid near the top of the 
solution by a silver rod riveted through its center. 

To prevent the disintegrated silver which is formed on the anode from 
falling upon the kathode, the anode shall be wrapped around with pure 
filter paper, secured at the back by suitable folding. 

The liquid shall consist of a neutral solution of pure silver nitrate, con- 
taining about 15 parts by weight of the nitrate to 85 parts of water. 

The resistance of the voltameter changes somewhat as the current passes. 
To prevent these changes having too great an effect on the current, some 
resistance, besides that of the voltameter, should be inserted in the circuit. 
The total metallic resistance of the circuit should not be less than 10 ohms. 

Method of making* a Measurement. — The platinum bowl is to 
be washed consecutively with nitric acid, distilled water, and absolute 
alcohol; it is then to be dried at 160° C, and left to cool in a desiccator. 
"When cold it is to be weighed carefully. 

It is to be nearly filled with the solution, and connected to the rest of the 
circuit by being placed on a clean copper support to which a binding-screw 
is attached 

The anode is then to be immersed in the solution so as to be well covered 
by it, and supported in that position ; the connections to the rest of the 
circuit are then to be made. 

Contact is to be made at the key, noting the time. The current is to be 
allowed to pass for not less than half an hour, and the time of breaking 
contact observed. ° 

The solution is now to be removed from the bowl, and the deposit washed 
with distilled water, and left to soak for at least six hours. It is then to be 
rinsed successively with distilled water and absolute alcohol, and dried in a 
hot-air bath at a temperature of about 160° C. After cooling in a desiccator 
it is to be weighed again. The gain in mass gives the silver deposited. 

To find the time average of the current in amperes, this mass, expressed 
in grammes, must be divided by the number of seconds during which the 
current has passed and by 0.001118. 

In determining the constant of an instrument by this method the current 
should l>3 kept as nearly uniform as possible, and the readings of the instru- 
ment observed at frequent intervals of time. These observations give a 
curve from which the reading corresponding to the mean current Ctime 
average of the current) can be found. 

The current is calculated from the voltameter results, corresponding to 
this reading. 

The current used in this experiment must be obtained from a battery and 
not from a dynamo, especially when the instrument to be calibrated "is an 
electrodynamometer. 

Specification B. — The Volt. 

The cell has for its positive electrode, mercury, and for its negative elec- 
trode, amalgamated zinc ; the electrolyte consists of a saturated solution of 



SPECIFICATION B. 



11 



zinc sulphate and mercurous sulphate. The electromotive force is 1.434 volts 
at 15° C, and, hetween 10° C. and 25° C, by the increase of 1° C. in tempera- 
ture, the electromotive force decreases by .00115 of a volt. 

1. Preparation of the Mercury. — To secure purity it should be 
first treated with acid in the usual manner, and subsequently distilled in 
vacuo. 

3. Preparation of the Zinc Amalgam. — The zinc designated in 
commerce as " commercially pure" can be used without further prepara- 
tion. For the preparation of the amalgam one part by weight of zinc is to 
be added to nine (9) parts by weight of mercury, and both are to be heated 
in a porcelain dish at 100° C. with moderate stirring until the zinc has been 
fully dissolved in the mercury. 

3. Preparation of the Mercurous Sulphate. — Take mercurous 
sulphate, purchased as pure, mix with it a small quantity of pure mercury, 
and wash the whole thoroughly with cold distilled water by agitation in a 
bottle ; drain off the water and repeat the process at least twice. After the 
last washing, drain off as much of the water as possible. (For further de- 
tails of purification, see Note A.) 

4. Preparation of the Zinc Sulphate Solution. — Prepare a 
neutral saturated solution of pure re-crystallized zinc sulphate, free from 
iron, by mixing distilled water with nearly twice its weight of crystals of 
pure zinc sulphate and adding zinc oxide in the proportion of about 2 per 
cent by weight of the zinc sulphate crystals to neutralize any free acid. The 
crystals should be dissolved by the aid of gentle beat, but the temperature 
to which the solution is raised must not exceed 30° C. Mercurous sulphate, 
treated as described in 3, shall be added in the proportion of about 12 per 
cent by weight of the zinc sulphate crystals to neutralize the free zinc oxide 
remaining, and then the solution filtered, while still warm, into a stock 
bottle. Crystals should form as it cools. 

5. Preparation of the Mercurous Sulphate and Zinc Sul- 
phate Paste. — For making the paste, two or three parts by weight of 
mercurous sulphate are to be added to one by weight of mercury. If the 
sulphate be dry, it is to be mixed with a paste consisting of zinc sulphate 
crystals and a concentrated zinc sulphate solution, so that the whole con- 
stitutes a stiff mass, which is permeated throughout by zinc sulphate crys- 
tals and globules of mercury. 

If the sulphate, however, be moist, only zinc sulphate crystals are to be 
added ; care must, however, be taken that these occur in excess, and are 
not dissolved after continued standing. The mercury must, in this case 
also, permeate the paste in little globules. It is advantageous to crush the 
zinc sulphate crystals before using, since the paste can then be better 
manipulated. 

To set up the Cell. —The containing glass vessel, represented in the 
accompanying figure, shall consist of two limbs closed at bottom, and joined 
above to a common neck fitted with a ground-glass 
stopper. The diameter of the limbs should be at 
least 2 cms. and their length at least 3 cms. The 
neck should be not less than 1.5 cms. in diameter. 
At the bottom of each limb a platinum wire of 
about 0.4 mm. in diameter is sealed through the 
glass 

To set up the cell, place in one limb mercury, 
and in the other hot liquid amalgam, containing 90 
parts mercury and 10 parts zinc. Tbe platinum 
wires at the bottom must be completely covered 
by the mercury and the amalgam respectively. On 
the mercury, place a layer one cm. thick of the 
zinc and mercurous sulphate paste described in 5. 
Both this paste and the zinc amalgam must then 
be covered with a layer of the neutral zinc sul- 
phate crystals one cm. thick. The whole vessel must 
then be filled with the saturated zinc sulphate solu- 
tion, and the stopper inserted so that it shall just 
touch it, leaving, however, a small bubble to guard 
against breakage when the temperature rises. 

Before finallv inserting the glass stopper, it is to be brushed round its 
upper edge with a strong alcoholic solution of shellac, and pressed firmly 
in place. (For details of filling the cell see Note B.) 




12 



SYMBOLS, UNITS, INSTRUMENTS. 



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DESCRIPTION OF INSTRUMENTS. 13 



Notes to the Specifications. 

(^4). The Mercurous Sulphate. — The treatment of the mercurous 
sulphate has for its object the removal of any mercuric sulphate which de- 
composes in the presence of water into an acid and a basic sulphate. The 
latter is a yellow substance — turpeth mineral — practically insoluble in 
water ; its presence, at any rate in moderate quantities, has no effect on the 
cell. If, however, it be formed, the acid sulphate is also formed. This is 
soluble in water, and the acid produced affects the electromotive force. The 
object of the washings is to dissolve and remove this acid sulphate, and for 
this purpose the three washings described in the specification will suffice in 
nearly all cases. If, however, much of the turpeth mineral be formed, it 
shows that there is a great deal of the acid sulphate present ; and it will then 
be wiser to obtain a fresh sample of mercurous sulphate, rather than to try 
by repeated washings to get rid of all the acid. 

The free mercury helps in the process of removing the acid ; for the acid 
mercuric sulphate attacks it, forming mercurous sulphate. 

Pure mercurous sulphate, when quite free from acid, shows on repeated 
washing a faint yellow tinge, which is due to the formation of a basic mer- 
curous salt distinct from the turpeth mineral, or basic mercuric sulphate. 
The appearance of this primrose yellow tinge, which is due to the formation 
of a basic mercurous salt distinct from the turpeth mineral, or basic mer- 
curic sulphate, may be taken as an indication that all the acid has been 
removed ; the washing may with advantage be continued until this tint 
appears. 

(B). filling' the Cell. — After thoroughly cleaning and drying the 
glass vessel, place it in a hot-water bath. Then pass through the neck of 
the vessel a thin glass tube reaching to the bottom to serve for the intro- 
duction of the amalgam. This tube should be as large as the glass vessel 
will admit. It serves to protect the upper part of the cell from being 
soiled with the amalgam, To fill in the amalgam, a clean dropping-tube 
about 10 cms. long, drawn out to a fine point, should be used. Its lower end 
is brought under the surface of the amalgam heated in a porcelain dish, and 
some of the amalgam is drawn into the tube by means of the rubber bulb. 
The point is then quickly cleaned of dross with filter paper, and is passed 
through the wider tube to the bottom, and emptied by pressing the bulb. 
The point of the tube must be so fine that the amlagam will come out only 
on squeezing the bulb. This process is repeated until the limb contains the 
desired quantity of the amalgam. The vessel is then removed from the 
water-bath. After cooling, the amalgam must adhere to the glass, and 
must show a clean surface with a metallic luster. 

For insertion of the mercury, a dropping-tube with a long stem will be 
found convenient. The paste may be poured in through a wide tube reach- 
ing nearly down to the mercury and having a funnel-shaped top. If the 
paste does not run down freely it may be pushed down with a small glass 
rod. The paste and the amalgam are then both covered with the zinc sul- 
phate crystals before the concentrated zinc sulphate solution is poured in. 
This should be added through a small funnel, so as to leave the neck of the 
vessel clean and dry. 

For convenience and security in handling, the cell may be mounted in a 
suitable case so as to be at all times open to inspection. 

In using the cell, sudden variations of temperature should, as far as 
possible, be avoided, since the changes in electromotive force lag behind 
those of temperature. 



CHAPTER III. 
DESCRIPTION Of INSTMUfllElI'TS. 

Although no attempt will be made here to fully describe all the different 
instruments used in electrical testing, some of the more important will be 
named and the more common uses to which they may be put mentioned. 

The four essential instruments for all electrical testing of which all other 
instruments are but variations, are: the battery, the galvanometer, the 
resistance-box, and the condenser, and following will be found a concise 
description of the more important types of each. 



14 SYMBOLS, UNITS. INSTRUMENTS. 



BATTERIES. 

These in their different forms are used as a source of current, not only for 
testing, but for many other purposes where smaller currents than those 
supplied by dynamos are required. 

Batteries are of two kinds, — primary, in which the E.M.F. is generated by 
chemicals in the cell itself ; and secondary, or storage, in which the elec- 
trical energy from some outside source is chemically stored in the battery, 
which becoines an independent source of current when the charging source 
is removed. Secondary batteries will be treated in a separate chapter. 

The types of primary battery most commonly in use in America are the 
gravity cell, used mostly for telegraph and closed-circuit work ; the Lelanclie 
cell, used for ordinary open-circuit work, as for door bells, telephone bells 
and other signals ; the Fuller cell, used for telephone and for telegraph pur- 
poses ; the chloride of silver cell, used largely for testing-purposes, as it is 
small enough to enable a large number of individual cells to be grouped in 
a box convenient for carrying about ; and the Edison-Lalande cell, useful 
in places requiring strong battery currents. 

Another form of battery that has come extensively into use since about 
1890 is the dry battery. This does not have the usual liquid solutions, but is 
partly tilled with a substance that will hold the moisture for a considerable 
time. There are, therefore, no liquids to spill ; and they make very handy 
sources of current for house bells, telephones, etc., where the users do not 
care to be bothered with creeping salts or any of the other troubles inherent 
in the common forms of liquid cells. 

The Gravity Cell. 

The elements are copper and zinc ; the solution is sulphate of copper, or 
" bluestone," dissolved in water. The usual form (see Fig. 2) is a glass jar, 
about 8 inches high and 6 inches diameter. The 
copper is made of two or more layers fastened in 
the middle, spread out, and set on edge in the 
bottom of the cell, the terminal being a piece of 
gutta-percha insulated copper wire extending up 
through the solution. 

The zinc is usually cast with fingers spread out, 
and a hook for suspending from the top of the jar 
as shown, the terminal being on top of the hook. 
This form of zinc is commonly called" crowfoot," 
and the battery often goes by that name. Some- 
times star-shaped zincs are suspended from a tri- 
pod across the top of the jar. The " bluestone " 
crystals are placed in the bottom of the jar about 
the copper, the jar then being filled with water to 
just above the " crowfoot " or zinc. A table- 
spoonful of sulphuric acid is added. A saturated 
solution of copper sulphate forms around the cop- 
FlG. 2. per ; and, after use, a zinc sulphate solution is 

formed around the zinc, and floats upon the cop- 
per sulphate solution. The line of separation between the two solutions 
is called the blue line. As the two solutions are kept separate because of 
their different specific gravities, the name " gravity cell " is employed. 

This cell does not polarize, and the E.M.F. is practically constant or uni- 
form at about 1 volt on a closed circuit. If the circuit is not closed, and the 
cell does not have work enough to prevent mixing of the two solutions, the 
copper sulphate coming in contact with the zinc will become decomposed ; 
the oxygen forming oxide of zinc, and the copper depositing on the zinc hav- 
ing an appearance like black mud. 

Care of the Crravity Cell. — For ordinary " local work " about three 
pounds of " bluestone" per cell is usually found best. When this is gone 
it is better to clean out the cell, and supply new solution, than to try to re- 
plenish. " Bluestone" crystals should not be smaller than a pea nor as 
large as an egg. In good condition the solution at the bottom should be a 
bright blue, changing to water-color above. A brownish color in any part 
denotes deterioration. 

To prevent evaporation of the solution it is well to pour a layer of good 
mineral oil over the top when the cell is first set up. This oil 6hould be 




BATTERIES. 



15 



odorless, free from naphtha or acid, and non-inflammable nnder 400° F. If 
oil is not used, dipping the top of the jar in melted paraffin for about an 
inch, will prevent the salts of the solution from climbing over the edge. In 
starting a new battery it is best to short circuit the cells for twenty-four or 
forty-eight hours to form zinc sulphate and lower the internal resistance. 
The internal resistance of the ordinary gravity cell is 2 to 3 ohms, depending 
on a number of conditions, such as the size of plates, the nearness together, 
and the nature of the solution. 

Never let the temperature of gravity cells get below 65° or 70° F., as the 
internal resistance increases very rapidly with a decrease in temperature. 

The JLeclanche Cell. 

This cell is one of the most commonly used outside of telegraphy, and up 
to the advent of the so-called dry cell was practically the only one in use for 
house and telephone work. The elements are zinc and carbon, with per- 
oxide of manganese about the carbon plate for a depolarizing agent. As 
usually constructed — for there are many modifications of the type — the jar 
is of glass, about 7 inches high and 5 inches in diameter, or sometimes square. 
The zinc is in the form of a stick, about a half inch diameter, by 7 inches 
long, and is placed in one corner of the jar in a solution of sal-ammoniac. 
The carbon plate is placed in a porous cup within the jar, and the space 
around the carbon in the cup is filled with small pieces of carbon and gran- 
ulated peroxide of manganese. The sal-ammoniac solution passes through 
the porous cup and moistens the contents. This cell will polarize if worked 
hard or short circuited, but recuperates quickly if left on open circuit for 
a while. The resistance of the Leclanche cell varies with its size and con- 
dition, but is generally less than one ohm. The initial E.M.F. is about 1.5 
volt. It is desirable not to use too strong a solution of sal-ammoniac, as 
crystals will be deposited on the zinc ; and not to let the solution get too 
weak, as chloride of zinc will form on the zinc ; both conditions will mate- 
rially increase the internal resistance of the cell, and impair its efficiency. 
Without knowing the dimensions of cells it is not possible to state the amount 
of sal-ammcniac to use ; but perhaps as good a way as any is to add it to 
the water until no more will dissolve, then add a little water so that the 
solution will be weaker than saturation. Keep all parts clean, and add 
sal-ammoniac and water when necessary. 1 

Chloride of Silver Cell. 

The elements of this cell are a rod of chemi- 
cally pure zinc, and a rod of chloride of silver 
in a water solution of sal-ammoniac. 

As ordinarily constructed the jar is of glass, about 2J 
inches long by § inch diameter, with the zinc and silver 
rods set in as per Fig. 3. The solution is poured in, 
and a plug of paraffin wax hermetically seals the jar. 
Suitable terminals are cast in or secured to the rods. 
As the greatest use made of these cells is for testing 
purposes in connection Avith a galvanometer, they are 
usually arranged in groups in a case, with terminals 
so arranged as to allow the use of as many as may be 
necessary for any particular test. Fig. 4 shows a port- 
able testing-battery of 50 chloride of silver cells, with 
attaching plugs and reversing-key. The E.M.F. of the 
chloride of silver cell is 1.03 volts, and the internal 
resistance varies with age, being about 4 ohms at first. 
Care should be taken not to short circuit these 
cells, as they are weakened thereby ; and where they 
are much used, frequent tests of individual cells for 
E.M.F. should be made ; they will vary considerably. 

Fig. 3. 
Culler Cell. 

The elements of this cell are zinc in a dilute solution of sulphuric acid, 
and carbon in a solution of electropoin. Electropoin consists of three parts 
bichromate of potash, one part sulphuric acid, and nine parts water. The 




16 



SYMBOLS, UNITS, INSTRUMENTS. 




zinc plate is in the form of a cone, and is placed in the bottom of a porous 
cup inside a glassjar. The carbon plate is outside the porous cup. 

About two ounces of mercury are placed in the porous cup with the zinc, 
for amalgamation, and the cup is tilled with a dilute solution of sulphuric 
acid. The outside jar is tilled with the electropoin. In this the carbon 
plate is immersed. 

The E.M.F is 2 volts, and the internal resistance is about half an ohm. 
The solution is originally of an orange color. When this becomes bluish in 
tint, add more crystals. Should the color be normal and the cell be weak, 
add fresh sulphuric acid. 

Edison-I^alamle Cell. 

The elements of this cell (see Fig. 5) are zinc, and copper oxide in a water 
solution of caustic potash. The plates are suspended side by side from the 
cover of the jar. The copper oxide, which is plated with a thin film of me- 
tallic copper to reduce the resistance when the cell is first started, is held in 



BATTERIES. 



17 



a frame attached to the cover. A layer of oil is 
poured on top of the solution to prevent creep- 
ing salts. The E.M.F. is low, starting at .78 
volt, and after working for a time it decreases. 
The internal resistance is also low, being about 
.025 ohm for the largest cell. Very strong cur- 
rents can be taken from this cell : for instance 
the cell having an E.M.F. of .75 volt and resist- 
ance of .025 ohm will produce 30 amperes on 
short circuit. The makers advise, in setting up 
the cell, that only one half of the sticks of 
caustic potash be placed in the jar first, and 
that water be then poured in up to within about 
an inch of the top of the jar. Then stir until 
the potash is dissolved, when one may add the 
remainder of the potash sticks, stirring as 
before. 

Dry Batteries. 

The general appearance of a cell of dry bat- 
tery is shown in Fig. 6, and the construction 
varies slightly in the different makes. The 

Burnley dry cell is made of a zinc tube (see Fig. 6) as one element, which acts 
also as the containing jar, a carbon cylinder is the negative element, and an 
exciting solution composed of 1 part sal-ammoniac, 1 part chloride of zinc, 3 
parts plaster, .87 parts flour, and 2 parts water. In constructing the cell a 
plunger somewhat larger than the carbon element is placed in the middle of 






Fig. 7. 



the zinc jar, and the above solution mixture poured in around it, quickly be- 
coming stiff, after which the plunger is withdrawn, the carbon inserted in 
place, and the surrounding space filled with another mixture consisting of 1 
part sal-ammoniac, 1 part chloride of zinc, 1 part peroxide of manganese, 1 
part granulated carbon, 3 parts plaster, 1 part flour, and 2 parts water. After 
the ingredients are all in place the top is sealed with bitumen or other suit- 
able compound. A terminal is fastened to the zinc cup, and another to the 
carbon plate. The E.M.F. of the Burnley cell is 1.4 volt ; the internal re- 
sistance about .3 ohm, and it gives practically constant E.M.F. during its life. 
The Gasner dry cell, shown in Fig. 7, consists of a zinc cup as the positive 



18 



Symbols, units, instruments. 



element, a cylinder composed of carbon and manganese for the negative 
element, and an exciting solution which becomes comparatively hard, made 
up of the following ingredients, viz. : 1 part by weight of oxide of zinc. 1 
part sal-ammoniac, 3 parts plaster, 1 part chloride of zinc, and 2 parts water. 

The E.M.F. and resistance are about the 
same as for the cell last described. 

Standard Cells. 

Clark Cell. — The form of cell called 
Clark, specifications for making which 
will be found in the chapter on units, 
is the one most used for a standard of 
E.M.F. The positive element is mercury, 
and the negative is amalgamated zinc, the 
electrolytes being saturated solutions of 
sulphate of zinc and mercurous sulphate. 
At 15° C. the E.M.F. is 1.434 volt, and 
between the points 10° and 25° C, the in- 
crease of 1° C. decreases the E.M.F. .00115 
volt. 

Carliart-Clark Cell.— This cell has 
the same elements as Clark, but the so- 
lution of zinc sulphate is saturated at 0° 
C. The E.M.F. is 1.440 volt, and the tem- 
perature coefficient about half that of the 
Clark cell. 

Weston Standard Cell. — The ele- 
ments are mercury and cadmium amalgam 
in a saturated solution of cadmium sul- 
phate. The E.M.F. is 1.019 to 1.022 volt, 
and the temperature coefficient 0.01 per 
cent per degree centigrade. These cells 
remain constant over long periods. Ob- 
servations extending over several months showed a variation of less than 
0.0001 volt. 

Arrangement of Battery Cells. 

Series. — When it is desired to obtain an E.M.F. greater than that of one 
cell, two or more are connected together in series ; that is, the positive termi- 
nal of one cell is connected to the negative terminal of the next, and so on 




Fig. 8. Carhart Clark Standard 
Cell. 



IS? 



1 — v/wvwwj cr? 



Fig. 9. Battery Cells in Series. 

until the number of cells required to produce the E.M.F. wanted are con- 
nected. For example, the E.M.F. of one cell of Leclanche is 1.47 volt, then 
10 cells connected in series as iw Fig. 9 would give an E.M.F. at the ex- 
treme terminals of 14.7 volts. 

multiple. — If it be desired to obtain more current strength, i.e., more 
amperes without change of E.M.F., then more cells must be placed along 
side the others, that is, in parallel with the first row ; each row or series, of 
cells producing the same E.M.F. and joined together at the ends, positive 



BATTERIES. 



19 



terminals to positive terminals, and negative to negative, adding their cur- 
rents together at the same E.M.F. as in Fig. 10 below. 

If still more current strength be needed, another series of cells may be 
added, and tbeir current added to the circuit, making tbree times the current 
of one series. 




EiG. 10. Battery Cells in Multiple. 



The reason for this is, that when two or more resistances are placed in 
parallel or multiple, the equivalent resistance is decreased, as is shown in 
another chapter. If the resistance of one series be 10 ohms, the resistance 
of two series in multiple would be one-half of ten, or 5 ohms ; that of three 
series in parallel, one-third, or 3.33 ohms ; and of four series, 2.5 ohms. 



Let 



E = E.M.F. of a single cell, 
r = internal resistance of one cell, 
R =z external resistance in a circuit. 



Then for n cells arranged in series, the current which will flow will be 
represented by the formula, 



If R is very small as compared with nr, then / = — , or the current is the 
same as that from one cell on short circuit. r 

If, as in telegraph work, nr is very small as compared with 7?, then 

nE 
Zzr — , or the current increases in proportion to the number of cells. 

The value of r is nearly inversely proportional to the area of the plates 
when fronting each other in the liquid, and directly as their distance apart. 
Therefore, if the area of the plate is increased a times, for one cell 



E 



aE 



r + aR 



Let 



A r = the total number of cells in the battery, 

ns = number of cells in each series, 

n P =z number of sets or series in parallel. 



Then the internal resistance of the whole battery 
n«r 

~ lip ' 

To find the best arrangement of a given number of cells (N) to obtain a 
maximum current (I) working through an external resistance (R), make 

— = R, or the internal resistance of the whole battery equal to R. 
rip 

.. . total E.M.F. 
In any circuit / = — r— > and for any arrangement 

tot<ii resist. 



20 SYMBOLS, UNITS, INSTRUMENTS. 

rieE n P nsE 



1 = 



n«r n 8 r -\- tipR 

n v """ 



When arranged for maximum current through a given external resistance fi, 

t /Nfi , . JNr 

lis = y — and np rr y — . 

To find the greatest current that can be obtained from a given number of 
cells (N ) through a given external resistance (11), 



2 1 fir 



▼ fir 



To find the number of cells in series (lis) and in parallel (n P ) required to 
give a current (/) through an external resistance (fi) and to have an effi- 
ciency (F). 

_,„. . „ External work 

Efficiency F = f „ ^ _ — 

Total work 

l*fi fi 



\n P ) n P 



The internal resistance of the whole battery is 
n s r _ fi(l — F) 
Tip ~ F 

and J =^T 

lfi 

na = EF 

Ir 

np ~ E(\-F)' 

These are instruments for measuring the magnitude or direction of electric 
currents. The term galvanometer can also be properly applied to the many 
types of indicating instruments, such as voltmeters and ammeters, where a 
needle or pointer is under the influence of some directive force, such as the 
earth's field, a spring, a weight, a permanent magnet, or other means, and 
is deflected from zero by the passing of an electric current through its 
coils. 

Nearly all galvanometers can be separated into two classes. The first is 
the moving-needle class. A magnetized needle of steel is suspended "with 
its axis horizontal so as to move freely in a horizontal plane. The suspen- 
sion is by means of a pivot or fiber of silk, of quartz, or of other material. 
The needle normally points in a north and south direction under the influence 
of the earth's magnetic field, or in the direction of some other field due to 
auxiliary magnets. Near to the needle, and frequently surrounding it, is 
placed a coil of wire whose axis is at right angles to the normal direction of 
the needle. When a current is passed through the coil the needle tends to 
turn into a new position, which lies between the direction of the original 
field and the axis of the coil. 

The second class is the moving coil or d'Arsonval class. A small coil is 
suspended by means of a fine wire between the poles of a magnet. Its axis 
is normally at right angles with the lines of the field. Current is led into 
the coil by means of the suspension wire, and leaves the coil by a flexible 
wire attached underneath it. 

The figure of merit of a galvanometer is (a) the current strength required 
to cause a deflection of one scale division ; or (b) it is the resistance that 
must be introduced into the circuit that one volt may cause a deflection of 
one scale division. This expression for the delicacy of a galvanometer is 



GALVANOMETERS. 



21 



insufficient unless the following quantities are also given : the resistance 
of the galvanometer, the distance of the scale from the mirror, the size of 
the scale divisions, and the time of vibration of the needle. 

The sensitiveness of a galvanometer is the difference of potential neces- 
sary to be impressed between the galvanometer terminals in order to pro- 
duce a deflection of one scale division. 

Moving'-Needle Galvanometers. 

(a.) The Tangent Galvanometer. If the inside diameter of the coil which 
surrounds a needle, held at zero by the earth's field, be at least 32 times the 
length of the needle, then the deflections of the needle which correspond to 
different current strengths sent through the coils, will be such that the 
current strengths will vary directly as the tangents of the angles of deflec- 
tion. Such an instrument is called a tangent galvanometer. It was for- 
merly much used for the absolute measurement of current. It has, however, 
many correction factors, some of which are of uncertain magnitude ; and, 
furthermore, for accuracy in the results yielded by it one must have an 
exact knowledge of the value of the horizontal component of the earth's 
magnetism. This quantity is continually changing, and is affected much 
by the presence of large masses of iron and the existence of heavy currents 
in the vicinity. 

Let r = the radius of a tangent galvanometer coil, in centimeters 
n = the number of turns in the coil, 
H= the horizontal intensity of the earth's magnetism, 
1= the current flowing in the coil in absolute units, and 
= the deflection of the needle, then 




Fig. 11. Tangent Galvanometers. 



22 



SYMBOLS, UNITS, INSTRUMENTS. 



2ir1l 



Htan i 



For convenience the term i.e., the strength of the field produced 

at the center of the coil by the unit of current, is called the constant of the 
galvanometer, and is represented by G, whence 

TT 

1= — ■ tan 9 

G 

The current in amperes equals 10 /. 

(b.) Thomson Galvanometers. The most sensitive galvanometers made are 
of a type due to Lord Kelvin. Fig. 12 shows one form of tbis instrument. The 
moving system consists of a slender quartz rod, to the center of which is 
fastened a small glass mirror. Parallel to the plane of the mirror, and at 

one end of the quartz tube, is fas- 
nua tened a complex of carefully se- 

lected minute magnetic needles. 
The north ends of those needles 
all point in the same direction. 
At the other end of the quartz 
tube is fastened a similar complex 
with the polarity reversed. Were 
the two complexes of exactly 
equal magnetic moment, then, 
when suspended in the earth's 
field, no directive action would be 
felt. In fact, this action is very 
small. The combination forms 
what is called an astatic system. 
Each magnetic complex is in- 
closed between two wire coils. 
The four coils are supplied with 
binding-posts, so as to permit of 
connection in series or in parallel. 
Current is sent through them in 
the proper direction, to produce 
in each case deflections the same 
way. Quartz fiber, which ex- 
hibits no elastic fatigue and 
which is very strong, is used as 
a suspension. An adjustable 
magnet is mounted on the top of 
the galvanometer. By means of 
it the directive action of the 
earth's field can be modified to 
any extent. Under weak direc- 
tive force the sensitiveness in- 
creases greatly, and the period of 
oscillation of the needle becomes 
long. The limit of sensitiveness 
is largely influenced by the pa- 
tience of the observer. 

For very precise work the de- 
flections of the needle are ob- 
served by means of a telescope 
and scale. Fig. 13 shows such an 
instrument. The moving mirror 
reflects an image of the scale into 
the objective of the telescope. 
Continuous work with the tele- 
scope is apt to injure the eyes, and is certainly tiresome. Where much gal- 
vanometer work is being done by the same person, a ray of light from a 
small electric, gas, or oil lamp is so directed as to be reflected from the 
mirror on the needle upon a divided scale. Such a lamp and scale is shown 
in Fig. 14. In order to bring the needle quickly to rest when under the in- 




FiG. 12, — Thomson Reflecting Astatic 
Galvanometer with Four Coils 



GALVANOMETERS. 



23 




Fig. 13. 




Fig. 14. 



24 



SYMBOLS, UNITS, INSTRUMENTS. 



fluence of a current, some method of damping must be employed. One 
method is to attach a mica vane to the moving system, and allow it to swing 
in an inclosed chamber which contains air or oil. Sometimes the moving 
needle is inclosed in a hollow made in a block of copper. The eddy currents 
induced by the moving needle react upon it and stop its swinging. 

Uloving'-Coil Galvanometers. 

These galvanometers are to be preferred in all cases except where the 
utmost of delicacy is required. In the most sensitive form, with permanent 
magnetic field, they can be made to deflect one millimeter with a scale dis- 
tance of one meter, when one microvolt is impressed between the terminals 
of the coil. This is sufficient for nearly all purposes. The sensitiveness can 
be further increased by using an electromagnetic field. The moving-coil 




Fig. 15. 



form of galvanometer has Jhe following good points : its readings are but 
slightly affected by the presence of magnetic substances in tbe vicinity, and 
are practically independent of tbe earth's Held ; the instrument can be easily 
made dead-beat ; and many forms are not much affected by vibrations. 
Fig. 15 shows a form of D'Arsonval galvanometer of high sensibility. The 
coil (shown at the right) is inclosed in an aluminum tube. Eddy currents 
are induced in this tube when the coil swings. They cause damping, and, 
with a proper thickness of tube, the system may be made aperiodic. 

Ballistic Galvanometers. 

Galvanometers are also used for measuring or comparing quantities of 
electricity such as flow in circuits when a condenser is discharged or mag- 
netic flux linkages are disturbed. The time of oscillation of the needle 



GALVANOMETERS, i * 25 



must in such cases be long as compared with the duration of the discharge. 
If there be no damping of the needle the quantities of electricity are pro- 
portional to the sines of half the angle of the first throws of the needle. All 
galvanometers have some damping. The comparison of quantities of elec- 
tricity can easily be made with galvanometers of moderate, or even strong 
damping. Absolute determination of quantity by means of the ballistic 
galvanometer requires great experimental precautions. (See the Galvano- 
meter, by E. L. Nichols.) 

"Voltmeters. 

These are indicating instruments which show the pressure impressed upon 
their terminals. They are in nearly all cases galvanometers of practically 
constant high resistance. Through them flow currents which are directly 
proportional to the impressed voltages. A pointer, connected to the mov- 
ing element, moves over a scale which is empirically graduated to cor- 
respond with the impressed voltages. The resistances of commercial 
voltmeters in ohms run from 10 to 150 times the full scale readings in 
volts. Thus a 150-volt voltmeter may have a resistance of from 1500 to 
22,500 ohms. The directive forces to bring the needle back to zero are 
generally obtained from springs, gravity, or magnets. Moving-coil instru- 
ments can be made so as to have high resistances and perfect damping. 
Moving-needle instruments are in common use for alternating current cir- 
cuits. The needle is of soft iron, and is given an alternating polarity by the 
currents flowing because of the impressed voltages, which are being meas- 
ured. Hot-wire voltmeters form a distinct class of instruments. The ex- 
pansions of a wire as a result of the passage of different currents of electricity 
are taken up by a spring. A pointer connected with the spring moves over 
an empirically divided scale. These instruments have a lower resistance 
per volt than the other types. They are quite dead beat. They record 
either alternating or direct currents. 

Ammeters. 

The scale of a voltmeter might be graduated and marked so as to indicate 
the currents passing through it instead of the volts impressed upon its 
terminals. It would then be an ammeter. To be of value its resistance 
must be small. Many ammeters consist of millivoltmeters connected to the 
terminals of shunts through which the currents to be measured are passed. 
The scales are graduated so as to indicate the currents passing through the 
shunts. The shunt type of instrument is particularly applicable to switch- 
boards. 

Northrup's Oscillating- Current Galvanometer. 

From catalogue of James G. Biddle. 

The working of this instrument depends upon the principle that when a 
metallic disk is suspended in a coil, the plane of the disk making with the 
plane of the coil an angle of about 45° the disk will tend to rotate, when 
alternating currents are sent through the coil, so as to increase this angle. 

The instrument is constructed to be exceedingly sensitive, to have a mini- 
mum of self-inductance, and practically no capacity. The disk is made of 
pure silver, about -fa?' thick and 9 mm. in diameter. Three coils are furnished 
with each instrument. One coil has about 20 turns of No. 20, one about 40 
turns of No. 42 ; and one about 100 turns of No. 36 B & S copper wire. Each 
coil is wound in two halves, so that the silver disk may be dropped down 
through the suspension tube and between the two halves of the coil. The 
inside diameter of the coils is about 1 mm. greater than the diameter of the 
disk. On either side of the hard-rubber upright piece which supports the 
coils are the poles of a permanent magnet. The coils are set at an angle of 
45° to the line joining the two poles, and the silver disk hangs so that its 
plane is in this line. 

The silver disk is fastened upon a light glass stem which carries a very small 
and thin mirror. This system is suspended upon an exceedingly fine quartz 
fiber. The complete period of swing of the system is about 12 seconds, and 
the magnet quickly dampens the oscillations to zero. Eor small angles the 



26 



SYMBOLS, UNITS, INSTRUMENTS. 



deflections are proportional to the square of the current and to its frequency. 
Hence as long as the frequency remains constant two currents are to each 
other as the square roots of the respective deflections indicating them. 

This instrument replaces and is far superior to the telephone in all cases 
where feeble, rapidly varying currents are to be detected or compared. 

The telephone fails to be of service when the frequency of the currents 
becomes very great ; the present instrument responds to currents of any 
frequency, including such as are set up in a Hertzian resonator. Since the 
self-induction of the instrument is very minute, it can be connected in series 
with any circuit in Avhich rapidly oscillating currents are passing, without 
appreciably changing their frequency. The instrument, therefore, serves 
in the performance of many Hertzian experiments. 

Galvanometer Slimnt Boxes, 

It is often desirable to use a galvanometer oi high sensibility for work 
demanding a much lower sensibility. Again, it may be convenient to cali- 
brate a galvanometer of low 
sensibility, while it would be 
inconvenient to calibrate a more 
sensitive one It is therefore 
useful to be able to change the 
sensibility in a known ratio. 
Convenience dictates that sim- 
ple ratios be used, and those 
almost universally taken are 10, 
100, and 1000 ; that is i, s \, or 9 | 9 , 
part of the current flowing is allowed to go through the galvanometer while 
the remainder is diverted through a shunt. In Fig. 16 let 
G = the resistance of the galvanometer, and 
S r= the resistance of the shunt, 

C 1 s 
the joint resistance of the two is 




VVW\A 



Fig. 16. 



then 

If 
if 
then 



G + S 

the total current flowing in the circuit, and 
the part flowing through the galvanometer, 



the Multiplying power of the shunt. 



_G_+S_ G 

i — s — s 

The resistance of a shunt which will give a certain multiplying power, n, is 

G 

equal to • Fig. 17 shows a form 

^ n — 1 

of shunt used with a galvanometer, al- 
though it is perfectly feasible to use an 
ordinary resistance box for the purpose. 
Messrs. Ayrton & Mather have developed 
a new shunt, which can be used with any 
galvanometer irrespective of its resist- 
ance : following is a diagram of it. 

A and B are terminals for the galvano- 
meter connections. B and C are the in- 
going and outgoing terminals for battery 
circuit. To short circuit G, place plugs 
in j and f. To throw all the current 
through G, put a plug in f only. To use 
the shunts, place a plug in h, and leave it 
there until through using. In this method 
it is not necessary to know the resistance 
of either G or r. The shunt box can 
therefore be used with any galvanometer. 
Temperature variations make no differ- 
ence, provided they do not take place Fig. 17. 
during one set of tests. The resistance 

r may be any number of ohms, but in order not to decrease the sensibility 
too much r should be at least as large as G. The resistance r is divided for 
use as follows : permanent attachments to the various blocks are made at 




points in the coil corresponding with 



1000, 100, 10 



ohms. 



RESISTANCES. 



27 




Fig. 18. Ayrton & Mather's Universal Shnnt. 



RE§ISTASCE§. 

The unit of resistance, the international ohm, is represented by the resist- 
ance of a uniform column of mercury 106.3 cm. long and 14.4521 grammes in 
mass, at 0° C ; but in practice it is not convenient to compare resistances 
with such a standard, and therefore sec- 
ondary standards (Fig. 19) of resistance 
are made up, and standardized with a 
great degree of precision. These second- 
ary standards are made of wire. The ma- 
terial must possess permanency of con- 
stitution and of resistivity, must have a 
small temperature coefficient of resistiv- 
ity, must have a small thermo-electric 
power when compared with copper, and 
should have a fairly high resistivity. 
Manganin when properly treated pos- 
sesses all of these qualities. Platinoid is 
also frequently used. An assemblage of 
standards of various convenient magni- 
tudes in a single case is called a resistance 
box, or rheostat. 

The form of resistance box most fre- 
quently met with is some type of " Wheat- 
stone's bridge," the theory of which is 
described elsewhere. 

The coils are usually of silk insulated 
wire wound non-inductively on spools, 
with the ends attached to brass blocks, so 
arranged that brass plugs can be inserted 
in a hole between two blocks, thus short circuiting the resistance of the 
particular bobbin over which the plug is placed. By non-inductive winding 
is meant that the wire is first doubled, then the closed end is placed on the 
bobbin and the wire wound double about the bobbin, by this method any 
electromagnetic action in one wire is neutralized by an equivalent action 
in the other, and there is no inductive effect when the circuit is opened 
or closed. , ,, . , 

The Post-office bridge, Figs. 20 and 21, is one of the most convenient 
forms. One arm of the bridge has separate resistances of the following 
values : 1, 2, 3, 4, 10, 20, 30, 40, 100, 200, 300, 400, 1000, 2000, 3000, and 4000 ohms. 




Fig. 19. 



28 



SYMBOLS, UNITS, INSTRUMENTS. 



Another arm is left open for the unknown resistance, x, which is to be 
measured. The remaining two arms each have three resistance coils of 

10, 100, and 1000 ohms respec- 
tively. Two keys are sup- 
plied with the P.O. bridge, 
one for closing the bat- 
tery circuit, and the other 
for closing the galvanometer 
circuit. The battery key 
should be closed first ; and in 
some instruments the two 
keys are arranged with the 
battery key on top of the gal- 
vanometer key, so that but 
one finger and one pressure 
are necessary. 

Prof. Anthony has devised 
a resistance box in which 
there are ten one ohm coils, 
10 tens, 10 hundreds, and 10 
thousands. Any number of 
The means of 




Pig. 20. Standard Resistance Coils with 
Wheatstone Bridge (Post Office Pattern), 
any group can be connected either in series or in multiple 
accomplishing this are seen clearly in the cut. 



Standard low 

Resistances of the ordinary form, 
which are smaller than ^ ohm, are 
very difficult to measure with great ac- 
curacy, owing to the uncertainty of the 
magnitude of the resistance of the leads 
and contact devices. Fortunately it is 
seldom that such a form ol resistance is 
used. Instead, the resistance between 
two potential points on a properly 
shaped conductor is used. Such stand- 
ard resistances of uj^ij, ^om ioo> etc -> 
ohms are now on the market, and are 
known as the Reichsanstalt form. They 
are made to carry very heavy currents. 
Fig. 23 shows such a resistance supplied 
with heavy contact terminals and a 
cooling coil. When this resistance is 
carrying a current, the drop between 
the two small terminals is such as 
would result from passing the same 
current through IO aoo ohrn. 



Resistances. 




Fig. 21. 



If one terminal of a 



Fig. 22 



< 4»\I»0:\*i:it». 

source of E.M.F. be connected to a conductor, 
and the other terminal be 
connected to another con- 
ductor adjacent to the 
first but insulated from 
it, it will be found that 
the two conductors ex- 
hibit a capacity for ab- 
sorbing a charge of elec- 
tricity that is somewhat 
analogous to the filling of 
a pipe with water before 
a pressure can be exerted. 
The charge will remain in 
the conductors after the 
removal of the source of 
supply. This capacity of 
the conductors to hold 
under a given E.M.F. a 




Standard Resistance Coils with Wheat 
stone Bridge (Anthony Form;. 



CONDENSERS. 



29 



charge of electricity is governed by the amount of surface exposed, by 
the nearness of the surfaces to each other, by the quality of the in- 
sulating material, and by the degree of insulation from each other. If 
the terminals of a battery be con- 
nected, through a battery and sensi- 
tive galvanometer, to a long sub- 
marine cable conductor and to the 
earth, it will be found that a very 
considerable time will elapse before 
the needle will settle down to a 
steady point. This sbows that the 
cable insulation has been filled with 
electricity ; and it is common in so 
measuring the insulation resistance 
of a cable to assume a standard length 
of time, generally three minutes, 
during which time such electrifica- 
tion shall take place. 

A condenser is an arrangement of 
metallic plates and insulation so 
made up that it will take a standard 
charge of electricity at a certain 
pressure. The energy represented by 
the charge seems to be stored up in 
the insulation between the conduct- 
ing plates in the form of a stress. This property of insulating materials 
to take on a charge of static electricity is known as inductive capacity, 
and a table in the section on the testing of capacity shows the specific in- 
ductive capacities of different substances. 

The unit of capacity is the international farad, which is defined as the 
capacity of a condenser which requires one coulomb (1 ampere for 1 second) 
to raise its potential from zero to one volt. 





Figs. 24 and 25. Queen Standard Condensers. 



As the farad is far larger than ever is met in practice, the practical unit 
is taken as one-millionth farad or the micro-farad. 

The commercial standard most in use is the § micro-farad, although 
adjustable condensers are often used, arranged so as to combine into many 
micro-farads or fractions of the same. Fig. 24 shows the ordinary a micro- 
farad condenser, and Fig. 25 one that is adjustable for different values. 
Diagram 26 shows an outline of the connections inside an adjustable con- 
denser. The ordinary commercial condenser is most usually made up of 



30 



SYMBOLS, UNITS, INSTRUMENTS. 



Mr 



r^i 



b6t 



ryi 



^ l 



~" - - 



Fig. 26. 




Fig. 27. Modified Mascart Electrometer. 



CONDENSERS. 



31 



sheets of tin foil separated from each other hy some insulator such as 
paraffined paper or mica. Every alternate sheet of foil is connected to a 
common terminal. As the capacity of a condenser depends upon the near- 
ness of the conductors to each other, and upon the area of the same, the 
insulating material is made as thin as possible, and still be safe from leakage 
or puncture. Many sheets of foil are joined together as described to make 
up the area. In adjustable condensers, the sheets are separated into bundles, 
and arranged so that any of them can be plugged in or out to add to or 
lessen the total capacity. If connected in multiple as shown, or if the 
positive side of one condenser be connected to the negative side of another, 
or a number of them are thus added together, then the condensers are said 
to be arranged in " cascade " or in series. This is seldom done unless it be 
to obtain greater variation in capacity. 

Electrometer. — Another instrument used somewhat in cable work, or 
where the measurement of electrostatic capacities or potentials is common, 
is the electrometer. A type of electrometer commonly used is the quadrant 
electrometer, for which we 
are indebted to Lord Kel- 
vin. The needle is a thin, 
flat piece of aluminium sus- 
pended in a horizontal po- 
sition by a thin metallic 
wire, in close proximity to 
four quadrants of thin sheet 
brass, that are supported on 
insulators without touching 
each other. Opposite quad- 
rants are connected by fine 
wires. A charge of elec- 
tricity is given the needle by 
connecting the suspension 
filament with a Leyden jar 
or other condenser. 

If the needle be charged 
positively it will be attracted 
by a negative charge and re- 
pelled by a positive charge. 
If, therefore, there be a dif- 
ference of potential between 
She pairs of quadrants, the 
needle will be deflected from 
zero. The usual mirror, 
scale, and lamp are used 
with this instrument, as in 
the case of the reflecting 
galvanometer. A form is 
shown in Fig. 27. 

Electrostatic Volt- 
meter. 

A modification of the elec- 
trometer, used for indicat- 
ing high, and in some cases low, alternating current potentials is the elec- 
trostatic voltmeter of Lord Kelvin. It is constructed on the principle 
of an air condenser. 

In the high potential instrument, Fig. 28, the needle is made of a thin 
aluminium plate suspended vertically on delicate knife-edges, with a pointer 
extending from the upper part to a scale. 

On either side of the needle, and parallel to its face, are placed two 
quadrant plates metallically connected and serving as one terminal of the 
circuit to be measured, while the needle serves as the other and opposite 
terminal. Any electi'ical potential difference between the needle and the 
plates will deflect the needle out of its neutral position. Calibrated weights 
can be. hung on the bottom of the needle to change the value of the scale 
indications. 

In the multicellular voltmeter, see Fig. 29, the needle consists of a number 
of thin plates, suspended horizontally and between corresponding quad- 




Fig. 28. Kelvin's Electrostatic Voltmeter, 



32 



SYMBOLS, UNITS, INSTRUMENTS. 




Fig. 29. Another Form of Lord 
Kelvin's Electrostatic Volt- 
meter. 

this fixed coil, and at right angles 
thereto, is suspended a movable coil 
of few turns. A carefully wound 
helical spring joins the movable coil 
to a torsion screw above the dial. A 
pointer on this torsion screw shows 
on the dial the degrees of angle 
through which it may be twisted. 
The lower ends of the movable coil 
dip into mercury cups to make con- 
nection with the fixed coil. If cur- 
rent flows through the two coils in 
series, the movable coil is turned 
from its position at right angles with 
the fixed coil, and tries to arrange 
itself in tbe same plane as the latter, 
according to law above. 



rant plates, thus multiplying 
the force tending to deflect the 
needles, and serving to indicate 
lower potential differences than 
the form described above is 
capable of. 

THE ELECTRO-DY- 
N AMOMLETjER. 

If currents be sent through 
two coils of wire, which are ca- 
pable of movement as regards 
each other, they will tend to 
place themselves in such a posi- 
tion as to bring the lines of force 
of their magnetic fields parallel 
to each other and in the same 
direction. The Siemen's electro- 
dynamometer acts according to 
this principle. 

Fig. 30 below shows the form 
most used in the United States. 
It consists of a fixed coil usually 
having two divisions, — one of a 
few turns of heavy wire for 
heavy currents, and another of 
many turns of finer wire for 
smaller currents. Outside of 



Fig. 30. Siemen's Electro- 
Dynamometer. 



ELECTRO-DYNAMOMETERS. 33 



The torsion screw is then turned in the opposite direction until the force 
of the spring overcomes the electrodynamic action of the coils, and the 
movable coil is brought to zero. 

If A be a constant depending upon the character of the torsion spring, / 
be the current, and d be the angle of deflection of the torsion screw to 
return the movable coil to zero, then 

I— A y/d. 
The electro-dynamometer is suited to measure alternating currents of ordi- 
nary frequencies. 

Wattmeter. — If the movable coil be of very fine wire, and have a coil 
of very high and non-inductive resistance in series with it, and if the fixed 
coil be of heavy wire, then the instrument may be used for measuring the 
work of a circuit in watts, by connecting the fixed coil in series with the 
circuit under test, and the movable coil across the terminals of the cir- 
cuit. In this case, if the voltage current be %, and the series current 
in the movable coil be i 2 , then the power equals K ifo, where K is a constant 
of the instrument. The two currents are supposed to be in phase with each 
other. If the movable coil be not brought back to zero, but a pointer con- 
nected with it be permitted to move over a graduated scale, the scale can be 
calibrated directly in watts. 

Weston's well-known wattmeter is constructed substantially on this 
principle. 

In order that a wattmeter (electro-dynamometer) may be reliable for 
measuring alternate-current power, it is needful that the fine-wire circuit, 
which is to be connected as a shunt to the apparatus under measurement, 
should have as little self-induction as possible in proportion to its resis- 
tance. The latter may be increased by adding auxiliary non-inductive 
resistances. The instrument must itself be so constructed that there shall 
not be any eddy currents set up by either circuit in the frames, supports, or 
case ; otherwise the indications will be false. 

Kelvin's Composite Electric Balance. 

This instrument is employed much as a standard for comparison of instru- 
ments used in all practical work for both continuous and alternating currents. 
It can be used as a voltmeter, ampere-meter, or wattmeter. The principle 




-O 

Fig. 31. Kelvin's Standard Composite Balance. 

of its action is similar to that of the electro-dynamometer. The attraction 
and repulsion between movable and stationary coils is balanced by the at- 
traction of gravity on a sliding weight connected with the movable coils. 

Above is a cut of the instrument in its latest form, and the diagram fol- 
lowing shows the theory on which the instrument works. 

In both cut and diagram the same letters indicate the same parts, a and 
b are two coils of silk-covered copper wire placed one above the other as 
shown, with their planes horizontal, and the whole being mounted on a 
slab of slate which is supported on leveling screws. 



34 



SYMBOLS, UNITS, INSTRUMENTS. 



Two coils c and d, of similar wire are made in rings that are secured to the 
ends of a balance beam B, which is suspended at its center by two flat liga- 
ments of fine copper wire. 

When for use with continuous currents two other coils, g and h, made of 
strip copper, and of cross-section heavy enough to carry large currents, say 
500 amperes, are secured to the base plate at the left in the same relative 
position as are the coils a and b at the right. When the instrument is to be 
used in the measurement of alternating currents, the coils g and h are made 
of two or three turns of a stranded copper conductor, each wire of which is 
insulated ; and, to as far as possible annul the effects of induction, the strand 
is given one turn or twist for each turn around the coil. 

The coils c and d of the balance are suspended equidistant between the 
right and left pairs of coils, with planes parallel to their planes, and centers 
coinciding with their centers. 

To Set the Balance. — Level the instrument with the adjustable legs, turn 
the stop screws back out of contact with the cross trunnions and front plate 
of the beam, leaving it free. 

To Use as Voltmeter or Centi-ampere Meter. — Connect the instrument to 
the circuit or source of E.M.F. through a non-inductive resistance is!, as shown 




WATT' 

WWWWV— J tf 



Fig. 32. Diagram of the Kelvin Composite Balance. 

in the preceding diagram, the resistance terminal to T and the other ter- 
minal to T y ; throw the switch H to the right to the " volt" contact. 

One of the weights v w x , vw 2 , v tt> s , is then used on the scale beam, and a 
is balance obtained. The current flowing in the instrument is then calcu- 
lated by a comparison of the scale-reading with the certificate accompanying 
the instrument. The volts E.M.F. at the terminals are calculated from the 
current flowing and the resistance in circuit, including the non-inductive 
resistance used, by Ohm's law, v = IE. 

To Use as Hekto-ampere Meter. — Turn the switch H to "watts," insert 
the thick wire coils in circuit with the current in such a way that the right- 
hand end of the beam rises. Use the " sledge " alone or the weight marked 
w.w. 

Terminals E and E x are then introduced into the circuit, and a measured 
current passed through the suspended coils g and h ; and the constants given 
in the certificate for the balance used in this way are calculated on the as- 
sumption that this current is .25 ampere. Any other current may be used, 
Bay / ampere, then the constant becomes t— .25 or 4 I. 



ELECTRO-DYNAMOMETERS. 35 



The current flowing in the suspended coils g and h may be measured by 
the instrument itself, arranged for the measurement of volts. To do this, 
first measure the current produced by the applied E.M.F. through the coils 
of the instrument and the external resistance, then turn the switch H to 
" watt," and introduce into the circuit a resistance equal to that of the fixed 
coils. 

To Use as a Wattmeter. — Insert the thick wire coils in the main circuit ; 
then join one end of the non-inductive resistance II to one terminal of the 
fine wire coils, and the other end of R to one of the leads ; the other termi- 
nal of the fine wire coils is connected to the other lead. The current flowing 
and the E.M.F. may now be determined by the methods described above. 
The watts can then be calculated from the E.M.F. of the leads, and the 
current flowing in the thick wire coils by the formula, 
P w = VI=iZB, 

Where i = current in the suspended coil circuit. 
/== current in the thick wire coils. 
Ji = resistance in the circuit. 

When working with alternating currents the non-inductive resistance JR 
must be large enough to prevent any difference of phase of the current 
flowing in the fine wire coils and the E.M.F. of the circuit. 



3G 



SYMBOLS, UNITS, INSTRUMENTS. 



Tal»lv of Doubled Square Roots for Lord Kelvin's 8tand- 
ai-d 131ectric Balances. 








100 


200 


300 


400 


500 


600 


700 


800 


900 







0.000 


20.00 


28.28 


34.64 


40.00 


44.72 


48.99 


52.92 


56.57 


60.00 





1 


2.000 


20.10 


28.35 


34.70 


40.05 


44.77 


49.03 


52.95 


56.60 


60.03 


1 


2 


2.828 


20.20 


28.43 


34.76 


40.10 


44.81 


49.07 


52.99 


56.64 


60.07 


2 


3 


3.464 


20.30 


2S.50 


34.81 


40.15 


44.86 


49.11 


53.03 


56.67 


60.10 


3 


4 


4.000 


20.40 


28.57 


34.87 


40.20 


44.90 


49.15 


53.07 


56.71 


60.13 


4 


5 


4.472 


20.49 


28.64 


34.93 


40.25 


44.94 


49.19 


53.10 


56.75 


60.17 


5 


6 


4.899 


20.59 


28.71 


34.99 


40.30 


44.99 


49,23 


53.14 


56.78 


60.20 


6 


7 


5.292 


20.69 


28.77 


35.04 


40.35 


45.03 


49.27 


53.18 


56.82 


60.23 


7 


8 


5.657 


20.78 


28.84 


35.10 


40.40 


45.08 


49.32 


53.22 


56.85 


60.27 


8 


9 


6.000 


20.88 


28.91 


35.16 


40.45 


45.12 


49.36 


53.25 


56.89 


60.30 


9 


10 


6.325 


20.98 


28.98 


35.21 


40.50 


45.17 


49.40 


53.29 


56.92 


60.33 


10 


11 


6.633 


21.07 


29.05 


35.27 


40.55 


45.21 


49.44 


53.33 


56.96 


60.37 


11 


12 


6.928 


21.17 


29.12 


35.33 


40.60 


45.25 


49.48 


53.37 


56.99 


60.40 


12 


13 


7.211 


21.26 


29.19 


35.38 


40.64 


45.30 


49.52 


53.40 


57.03 


60.43 


13 


14 


7.483 


21.35 


29.26 


35.44 


40.69 


45.34 


49.56 


53.44 


57.06 


60.46 


14 


15 


7.746 


21.45 


29.33 


35.50 


40.74 


45.39 


49.60 


53.48 


57.10 


60.50 


15 
16 


16 


8.000 


21.54 


29.39 


35.55 


40.79 


45.43 


49.64 


53.52 


57.13 


60.53 


17 


8.246 


21.63 


29.46 


35.61 


40.84 


45.48 


49.68 


53.55 


57.17 


60.56 


17 


18 


8.485 


21.73 


29.53 


35.67 


40.89 


45.52 


49.72 


53.59 


57.20 


60.60 


18 


19 


8.718 


21.82 


29.60 


35.72 


40.94 


45.56 


49.76 


53.63 


57.24 


60.63 


19 


20 


8.944 


21.91 


29.66 


35.78 


40.99 


45.61 


49.80 


53.67 


57.27 


60.66 


20 


21 


9.165 


22.00 


29.73 


35.83 


41.04 


45.65 


49.84 


53.70 


57.31 


60.70 


21 


22 


9.381 


22.09 


29.80 


35.89 


41.09 


45.69 


49.88 


53.74 


57.34 


60.73 


22 


23 


9.592 


22.18 


29.87 


35.94 


41.13 


45.74 


49.92 


53.78 


57.38 


60.76 


23 


24 


9.798 


22.27 


29.93 


36.00 


41.18 


45.78 


49.96 


53.81 


57.41 


60.79 


24 


25 


10.000 


22.36 


30.00 


36.06 


41.23 


45.83 


50.00 


53.85 


57.45 


60.83 


25 
26 


26 


10.198 


22.45 


30.07 


36.11 


41.28 


45.87 


50.04 


53.89 


57.48 


60.86 


27 


10.392 


22.54 


30.13 


36.17 


41.33 


45.91 


50.08 


53.93 


57.52 


60.89 


27 


28 


10.583 


22.63 


30.20 


36.22 


41.38 


45.96 


50.12 


53.96 


57.55 


60.93 


28 


29 


10.770 


22.72 


30.27 


36.28 


41.42 


46.00 


50.16 


54.00 


57.58 


60.96 


29 


30 


10.954 


22.80 


30.33 


36.33 


41.47 


46.04 


50.20 


54.04 


57.62 


60.99 


30 
31 


31 


11.136 


22.89 


30.40 


36.39 


41.52 


46.09 


50.24 


54.07 


57.65 


61.02 


32 


11.314 


22.98 


30.46 


36.44 


41.57 


46.13 


50.28 


54.11 


57.69 


61.06 


32 


33 


11.489 


23.07 


30.53 


36.50 


41.62 


46.17 


50.32 


54.15 


57.72 


61.09 


33 


34 


11.662 


23.15 


30.59 


36.55 


41.67 


46.22 


50.36 


54.18 


57.76 


61.12 


34 


35 


11.832 


23.24 


30.66 


36.61 


41.71 


46.26 


50.40 


54.22 


57.79 


61.16 


35 


36 


12.000 


23.32 


30.72 


36.66 


41.76 


46.30 


50.44 


54.26 


57.83 


61.19 


36 


37 


12.166 


23.41 


30.79 


36.72 


41.81 


46.35 


50.48 


54.30 


57.86 


61.22 


37 


38 


12.329 


23.49 


30.85 


36.77 


41.86 


46.39 


50.52 


54.33 


57.90 


61.25 


38 


39 


12.490 


23.58 


30.92 


36.82 


41.90 


46.43 


50.56 


54.37 


57.93 


61.29 


39 


40 


12.649 


23.66 


30.98 


36.88 


41.95 


46.48 


50.60 


54.41 


57.97 


61.32 


40 


41 


12.806 


23.75 


31.05 


36.93 


42.00 


46.52 


50.64 


54.44 


58.00 


61.35 


41 


42 


12.961 


23.83 


31.11 


36.99 


42.05 


46.56 


50.68 


54.48 


58.03 


61.38 


42 


43 


13.115 


23.92 


31.18 


37.04 


42.10 


46.60 


50.71 


54.52 


58.07 


61.42 


43 


44 


13.266 


24.00 


31.24 


37.09 


42.14 


46.65 


50.75 


54.55 


58.10 


61.45 


44 


45 


13.416 


24.08 


31.30 


37.15 


42.19 


46.69 


50.79 


54.59 


58.14 


61.48 


45 


46 


13.565 


24.17 


31.37 


37.20 


42.24 


46.73 


50.83 


54.63 


58.17 


61.51 


46 


47 


13.711 


24.25 


31.43 


37.26 


42.28 


46.78 


50.87 


54.66 


58.21 


61.55 


47 


48 


13.856 


24.33 


31.50 


37.31 


42.33 


46.82 


50.91 


54.70 


58.24 


61.58 


48 


49 


14.000 


24.41 


31.56 


37.36 


42.38 


46.86 


50.95 


54.74 


58.28 


61.61 


49 


50 


14.142 


24.49 


31.62 


37.42 


42.43 


46.90 


50.99 


54.77 


58.31 


61.64 


50 



DOUBLED SQUARE ROOTS. 



37 








100 


200 


300 


400 


500 


600 


700 


800 


900 




51 


14.283 


24.58 


31.69 


37.47 


42.47 


46.95 


51.03 


54.81 


58.34 


61.68 


51 


52 


14.422 


24.66 


31.75 


37.52 


42.52 


46.99 


51.07 


54.85 


58.38 


61.71 


52 


53 


14.560 


24.74 


31.81 


37.58 


42.57 


47.03 


51.11 


54.88 


58.41 


61.74 


53 


54 


14.697 


24.82 


31.87 


37.63 


42.61 


47.07 


51.15 


54.92 


58.45 


61.77 


54 


55 


14.832 


24.90 


31.94 


37.68 


42.66 


47.12 


51.19 


54.95 


58.48 


61.81 


55 


56 


14.967 


24.98 


32.00 


37.74 


42.71 


47.16 


51.22 


54.99 


58.51 


61.84 


56 


57 


15.100 


25.06 


32.06 


37.79 


42.76 


47.20 


51.26 


55.03 


58.55 


61.87 


57 


58 


15.232 


25.14 


32.12 


37.84 


42.80 


47.24 


51.30 


55.06 


58.58 


61.90 


58 


59 


15.362 


25.22 


32.19 


37.89 


42.85 


47.29 


51.34 


55.10 


58.62 


61.94 


59 


60 


15.492 


25.30 


32.25 


37.95 


42.90 


47.33 


51.38 | 55.14 


58.65 


61.97 


60 


61 


15.620 


25.38 


32.31 


38.00 


42.94 


47.37 


51.42 


55.17 


58.69 


62.00 


61 


62 


15.748 


25.46 


32.37 


38.05 


42.99 


47.41 


51.46 


55.21 


58.72 


62.03 


62 


63 


15.875 


25.53 


32.43 


38.11 


43.03 


47.46 


51.50 


55.24 


58.75 


62.06 


63 


64 


16.000 


25.61 


32.50 


38.16 


43.08 


47.50 


51.54 


55.28 


58.79 


62.10 


64 


65 


16.125 


25.69 


32.56 


38.21 


43.13 


47.54 


51.58 


55.32 


58.82 


62.13 


65 


66 


16.248 


25.77 


32.62 


38.26 


43.17 


47.58 


51.61 


55.35 


58.86 


62.16 


66 


67 


16.371 


25.85 


32.68 


38.31 


43.22 


47.62 


51.65 


55.39 


58.89 


62.19 


67 


68 


16.492 


25.92 


32.74 


38.37 


43.27 


47.67 


51.69 


55.43 


58.92 


62.23 


68 


69 


16.613 


26.00 


32.80 


38.42 


43.31 


47.71 


51.73 


55.46 


58.96 


62.26 


69 


70 


16.733 


26.08 


32.86 


38.47 


43.36 


47.75 


51.77 


55.50 


58.99 


62.29 


70 


71 


16.852 


26.15 


32.92 


38.52 


43.41 


47.79 


51.81 


55.53 


59.03 


62.32 


71 


72 


16.971 


26.23 


32.98 


38.57 


43.45 


47.83 


51.85 


55.57 


59.06 


62.35 


72 


73 


17.088 


26.31 


33.05 


38.63 


43.50 


47.87 


51.88 


55.61 


59.09 


62.39 


73 


74 


17.205 


26.38 


33.11 


38.68 


43.54 


47.92 


51.92 


55.64 


59.13 


62.42 


74 


75 


17.321 


26.46 


33.17 


38.73 


43.59 


47.96 


51.96 


55.68 


59.16 


62.45 


75 


76 


17.436 


26.53 


33.23 


38.78 


43.63 


48.00 


52.00 


55.71 


59.19 


62.48 


76 


77 


17.550 


26.61 


33.29 


38.83 


43.68 


48.04 


52.04 


55.75 


59.23 


62.51 


77 


78 


17.664 


26.68 


33.35 


38.88 


43.73 


48.08 


52.08 


55.79 


59.26 


62.55 


78 


79 


17.776 


26.76 


33.41 


38.94 


43.77 


48.12 


52.12 


55.82 


59.30 


62.58 


79 


80 


17.889 


26.83 


33.47 


38.99 


43.82 


48.17 


52.15 


55.86 


59.33 


62.61 


80 


81 


18.000 


26.91 


33.53 


39.04 


43.86 


48.21 


52.19 


55.89 


59.36 


62.64 


81 


82 


18.111 


26.9S 


33.59 


39.09 


43.91 


48.25 


52.23 


55.93 


59.40 


62.67 


82 


83 


18.221 


27.06 


33.65 


39.14 


43.95 


48.29 


52.27 


55.96 


59.43 


62.71 


83 


84 


18.330 


27.13 


33.70 


39.19 


44.00 


48.33 


52.31 


56.00 


59.46 


62.74 


84 


85 


18.439 


27.20 


33.76 


39.24 


44.05 


48.37 


52.35 


56.04 


59.50 


62.77 


85 


86 


18.547 


27.28 


33.82 


39.29 


44.09 


48.41 


52.38 


56.07 


59.53 


62.80 


86 


87 


18.655 


27.35 


33.88 


39.34 


44.14 


48.46 


52.42 


56.11 


59.57 


62.83 


87 


88 


18.762 


27.42 


33.94 


39.40 


44.18 


48.50 


52.46 


56.14 


59.60 


62.86 


88 


89 


18.868 


27.50 


34.00 


39.45 


44.23 


48.54 


52.50 


56.18 


59.63 


62.90 


89 


90 


18.974 


27.57 


34.06 


39.50 


44.27 


48.58 


52.54 


56.21 


59.67 


62.93 


90 


91 


19.079 


27.64 


34.12 


39.55 


44.32 


48.62 


52.57 


56.25 


59.70 


62.96 


91 


92 


19.183 


27.71 


34.18 


39.60 


44.36 


48.66 


52.61 


56.28 


59.73 


62.99 


92 


93 


19.287 


27.78 


34.23 


39.65 


44.41 


48.70 


52.65 


56.32 


59.77 


63.02 


93 


94 


19.391 


27.86 


34.29 


39.70 


44.45 


48.74 


52.69 


56.36 


59.80 


63.06 


94 


95 


19.494 


27.93 


34.35 


39.75 


44.50 


48.79 


52.73 


56.39 


59.83 


63.09 


95 


96 


19.596 


28.00 


34.41 


39.80 


44.54 


48.83 


52.76 


56.43 


59.87 


63.12 


96 


97 


19.698 


28.07 


34.47 


39.85 


44.59 


48.87 


52.80 


56.46 


59.90 


63.15 


97 


98 


19.799 


28.14 


34.53 


39.90 


44.63 


48.91 


52.84 


56.50 


59.93 


63.18 


98 


99 


19.900 


28.21 


34.58 


39.95 


44.68 


48.95 


52.88 


56.53 


59.97 


63.21 


99 


100 


20.000 


28.28 


34.64 


40.00 


44.72 


48.99 


52.92 


56.57 


60.01) 


63.25 


100 



MEASUREMENTS. 

REilSTAKCE MEA§UREMEHfTi. 

Obm's I^aw is the foundation of all electrical testing, and is written in 
the following forms : — 

E = IR; 

where 1= the current strength in amperes, 

R — the resistance in ohms, 
and E ■=. the electromotive force in volts. 

The Resistance of Multiple Circuits equals the reciprocal of 
the sum of the reciprocals of the resistances of each circuit individually. 

In the figure the joint resistance R± of the two cir- 
cuits r and i\, between a and b. 

R t = — ; — i and the resistance required to he joined 
r -f- i\ 

in parallel with r to give R t is 

_ r x R x 
r i - r _ El 
and the total resistance of the figure, neglecting that 
of the battery and connections, 

= B + r -X?±. 

r + r^ 

The joint resistance of any number of resistances in parallel, as, a, b, c, d, 
e, etc., will be 

1 

a ,1.1.1 . 

a 6 ' c ' d 

.Joint insulation Resistance. — If n = total insulation resistance 
of the figure, and y = insulation resistance of the 
section from a to c, then the insulation resistance 
x of the section from b to c will be 




> 



_ y X n _ 
y — n 

" Tlie Current Strengths in Parallel or 

- bI °- z ' Multiple Circuits are in proportior co the con- 

ductivities of the separate branches, or inversely 
proportional to their respective resistances. 
In the figure, total current flowing in R, 

I=E r + r 



Rr -f- Rr x -f- rr 1 
E 



Rr -\- Rr 1 -f- rr 1 

1 — Rr -\- Rr x -\- rr x ' 

Wheatstonc's Rruliie. — For accurate meas- 
urement of resistance the Wheatstone's bridge 
method is more generally used than any other. 

38 




PRECISE COMPARISON OF SMALL RESISTANCES. 



39 




The diagram Fig. 4 shows the theoretical connections of the bridge. 

In the diagrams Fig. 4 and Fig. 6 a, b, and R are known resistances, and 
x the unknown resistance to be meastired. G is 
the galvanometer ; B is a battery of several cells, 
the number being varied according to the resist- 
ance of x. a and b are adjustable, but may be 
left equal to each other ; when R may be ad- 
justed until there is no deflection of the galva- 
nometer needle. 
Then a : b : : R : x 

and ax = bR 

bR 

and x =. 

a 

Fig. 4. Note. — Always close the battery key before 

closing the galvanometer key, to avoid an in- 
stantaneous deflection of the galvanometer, which may be due to inductance 
in one of the arms of the bridge. This deflection might occur even though 
the resistances be properly balanced. 

If a = b the value of x is the same as R. Should x be higher than the 
capacity of R, or lower than its smallest unit, then a and b can be arranged 
to multiply or divide the resistance value of R, and the equation still remains 

a : b : : R : x. 
For example, 

let a = 10 

b = 1000 
R = 200 ; 
then 10: 1000:: 200: a; 

10ic = 200,000 
x = 20,000 ; 



and in practice the ratio a 
by 100. 
Again, let 



100, and any reading as R would be multiplied 

a = 1000 

6 = 10 

iZ = 200 
1000: 1Q::200:# 
1000^ = 2000 

x = 2; 

and the ratio a : 6 = yj^. and any reading as R would be divided by 100. 

Post-Office Bridge. — A very convenient form of Wheatstone's bridge 
is shown in Fig. 5, of which the connections are shown in^diagram 6. The 





ioojioo dp 80 so I 

I Mo I iTo oo-3uj> o ao oo 



Fig. 5. 




letters and figures are the same as in the former diagrams, and will need no 
further explanation. 



40 



MEASUREMENTS. 



Fig. 7 is a form of bridge designed by Prof. Anthony which employs a 
smaller number of plugs than are used in ordinary forms of bridges, and 
thereby dispenses with much of the accompanying contact resistance. 




£^p ^^^^ 



Fig. 7. 



Slide-wire Bridsre. — A very convenient form of bridge for ordinary 
use where extreme accuracy is not de- 
manded is the slide-wire bridge, shown in 
Fig. 8. It consists of a wire one meter 
long and about 1.5 mm. diameter stretched 
parallel with a meter scale divided into 
millimeters. A contact key is so arranged 
as to be moved along the wire so that con- 
tact with it can be made at any point. 

A known resistance R is connected as 
shown ; x is the unknown resistance ; the 
galvanometer and the battery are joined 
up as shown in the figure ; after closing 
the key k l the contact 3 is then moved 
along the wire until the galvanometer needle returns to zero : 
then again ; a : b : : R : x, 

bR 

and x = 




Tlie Cary-Foster !?9 <c tSiod . — For the very precise comparison of 
nearly equal resistances of from 1 to 100 ohms this method yields exquisite 
results. In Fig. 9, S x and S 2 represent the two 
nearly equal resistances to be compared, andi? lt 
R 2 represent nearly equal resistances, which, for 
best results, should not differ much in magnitude 
from S t and S 2 . S x and S 2 are connected by a 
slide-wire whose resistance per unit length p is 
known. The battery and galvanometer are con- 
nected as in the diagram. A balance is obtained 
by moving the contact c along the stretched Avire. 
Suppose the length of the wire on the left-hand 
side to the point of contact to be a units. Then 
exchange S t and S 2 for each other without alter- 
ing any other connections in the circuit. Upon 
producing a new balance, let a x be the length of 
wire to the left of the contact. 

Then S x = S 2 + (a — a-J p. 

Special commutators are upon the market which have for their purpose 
the easy exchange of Si and S 2 . 

To avoid thermal effects, which are quite considerable with resistances 
made of some materials, the battery should be commutated for each position 
of the resistances to be compared. The readings for the two balances ac- 
companying the battery commutation should be averaged. 



< 


T S V£ 

(g) ^\ 


a 


6 


T 


\< j^h 




|, ^. 


Fig. 9. 
B 


Cary-Foster 
ridge. 



PRECISE COMPARISON OF SMALL RESISTANCES. 



41 




Double Bridge. 



Thomson's I>onl>le Bridg-e. — If the resistances in a Wheatstone's 
bridge be much less than one ohm in magnitude, the accuracy of the results 

obtained is inferior. Samples of 
copper or other wires of moderate 
lengths and diameters have such 
small resistances that the resistiv- 
ities of the materials of which 
they are constructed cannot be 
determined satisfactorily by this 
method. Thomson designed a 
modified form of bridge which 
gives very satisfactory results. 
Its construction is represented 
diagrammatically in Fig. 10, where 
the unknown low resistance x is 
compared with a standard low re- 
sistance R. R and x represent 
the resistances of measured lengths of standard wire and test wire respec- 
tively. These two wires are firmly joined at y. The uncertainty of the 
exact point of separation between them would make it difficult to connect 
the galvanometer so as to yield a reliable balance. By the insertion of two 
auxiliary resistances n and o of such magnitudes that n : o — R : x = a : b, 
and by connecting the galvanometer through the key k t to a point between 
n and o, results of very good accuracy may be obtained. 

Precise Comparison of Very Small Resistances. — For com- 
paring the low resistances of ammeter shunts, etc., with standard side ter- 
minal resistances of the Reichsanstalt 
form, the method of Sheldon yields 
very accurate results. The unknown 
resistance x, Fig. 11, which may be as- 
sumed to be supplied with branch po- 
tential points a b, is connected by heavy 
conductors in series with a standard re- 
sistance R, having potential points c d. 
From the two free terminals T T 1 of 
these resistances are shunted two 10,000 
ohm resistance boxes S P, adjusted to 
the same normal temperature, and 
wound with wire of the same or negli- 
gable temperature coefficient, and con- 
nected in series. From the point of 

connection e, between the two boxes, connection is made to one terminal of 
the galvanometer g, the other terminal being connected successively with 
the potential points a, b, c, and d. At the outset all the plugs are removed 
from the box S, and all are in place in the box P. After connecting T and 
T 1 with a source of heavy current, plugs are transferred from one box to the 
corresponding holes in the other box (this keeps the total resistance in the 
two boxes constant) until no deflection is observed in the galvanometer. 
This operation is repeated for each of the potential points a, b, c, and d. Rep- 
resenting the resistances in the box S on the occasion of each of these bal- 
ances by Sa, Sb, Sc, and Sd respectively, we have the following expression 
for the value of the unknown resistance : — 




Measurement. 



Sb 



Sd 



R. 



Differential Galvanometer Method. — In galvanometers hav- 
ing two coils wound side by side, when two separate and equal currents are 
sent through the coils, but in opposite directions, the needle will not move. 
If the currents are unequal the needle will be deflected in proportion to the 
difference of current strength ; and, as the current can be varied by varying 
the resistance, this instrument will serve for comparing an unknown resist- 
ance with a known resistance. 

To determine if the coils have equal effect on the needle, connect them in 
series opposition, and pass a current through them ; if there be any deflec- 
tion of the needle one of the coils will have to be moved until the needle 
stands at zero ; or with the coils in multiple a resistance can be placed in 
series with the coil taking the most current. 



42 



MEASUREMENTS. 



RESISTANCE Or WIRES. 

By Simple Substitution. — Place the resistance to be measured in 
series with a galvanometer and battery or other source of steady current, 
and note the deflection of the needle. Replace the unknown resistance with 
a known adjustable resistance, and change the latter resistance until the 
same deflection of the galvanometer needle is obtained as with the unknown 
resistance ; then the unknown resistance equals the value of the known 
resistance that is necessary to produce the same deflection. 

Other methods and applications are shown in the section on voltmeter 
tests. 

RESISTANCE OE CiA LVAXOJIETERS. 



When a second galvanometer is available, by far the most simple and sat- 
isfactory method is to measure the resistance of the galvanometer by any 
of the ordinary Wheatstone's bridge methods. Take the temperature at 
the same time, and, if the instrument has a delicate system, remove the 
needle and suspension. 
Half Reflection Method. — Connect the galvanometer in series with 
a resistance r and battery as in the following figure. 
r Note the deflection d ; then increase r so that the new 

deflection d x will be one-half the first, or - = d x ; call 



? & 



the new resistance r-, ; then 

Resistance of Galvanometer = r, — 2r. 
-p IGr 12 If tne instrument be a tangent galvanometer, then 

d and d x should represent the tangents of the deflec- 
tions. 
Thomson's Method. — Connect the galvano- 
meter, as a? in a Wheatstone's bridge, as in Fig. 13. 
Adjust r until the deflection of G is the same, 
whether the key is closed or open. 

G = r b . 
a 

The result is independent of the resistance of the 
battery. The battery should be connected from the 
junction of the two highest resistances to that of 
the two lowest. 




| — ^V&V^Aa 



RESISTANCE OE RATTERIES. 

Condenser Method. — For this test is needed a condenser C, a ballistic 
galvanometer G, a double contact key fc l5 a resistance R, 
of about the same magnitude as the supposed resistance 
of the battery B, and a single contact key k 2 . Connect as 
in the following figure. With the key k 2 open, press the 
key &!, and observe the throw 6^ in the galvanometer. 
Then, after the needle has come to rest, with key k 2 
closed, repeat the operation observing the throw 2 . 
Then the resistance of the battery 

7 > 0i - e -i 



B 




Reduced Reflection Method. — Connect the 
battery B in circuit with a galvanometer G and a resist- 
ance r as in Fig. 15. Note the deflection d, and then in- 
crease r to r x and note the smaller deflection d A ; then, if the deflections of 
the galvanometer be proportional to the currents, 
B= rxd 1 -rd_ e 



B^= 




If r t is such that d t = ^ » 

then B —r x — (2r + G). 



RESISTANCE OF AERIAL LINES. 



43 



The E.M.F. of the battery is supposed to remain unaltered, during the 
measurement. 

IHance'g Method. — Connect the battery as a: 
in Wheats tone's bridge as in Fig. 16. Adjust r until 
the deflection of G is the same whether the key be 
closed or open. 

Then B = r-. 

a 

The galvanometer should be placed between the 
junction of the two highest resistances and that of 
the two lowest. 

Resistance of Battery while Working 1 . 

— Connect the battery B with a resistance r, and 

also in parallel with a condenser C, galvanometer G, and key 1c ; shunt the 

battery through s with key l\, as in Fig. 17. 
Close the key 7c, and note the deflection d of 

the galvanometer, keeping k closed, close l\ and 

note dj, the deflection in the opposite direction. 

Then the battery resistance 

B = s— * 





d-d,— 



d,s 



d s 
If r be large, the term — — is negligible, and 



B 



<*i 



d—dS 

s being the multiplying power of the shunt. 

Workshop Method, Applicable as well to Dynamos.- With 
dynamo or battery on open circuit, take the voltage across the terminals 
with a voltmeter, and call it d ; take another reading d 1 at the same points 
with the battery or dynamo working on a known resistance r : then the in- 
ternal resistance B = — — — - 1 r. 

d x 

In the case of storage batteries, if the current / be read from an inserted 
ammeter when charging, the resistance of the battery is 

A — d 



B — 



and when discharging 



/ 
d — d x 



RESISTANCE OF AERIAL LIBTES OR HOUSE 
CIRCUITS. 

Conductor Resistance. — When the circuit has metallic return, it is 
easily measured by any of the Wheatstone's bridge methods, or, if the circuit 
conductor can be supplied with current through an ammeter, then the fall 
of potential across the ends of the con- 
ductor will give a measure of the resistance 
by ohms law, viz., 

-r, . . drop in volts 

Resistance — — -r — . 

current 

If the circuit has earth return as in tele- 
graph and some telephone circuits, then 
place far end of the line to earth, and con- 
Earth^ nect witn bridge as in Fig. 18. 

Then the total resistance x of the line and 

earth, is x = r '— . 




--Earth' 



Fig. 18. 



If a second line be available, the resistance of the first line can be deter 
mined separated from that of earth, as well as the resistance of earth. 



44 MEASUREMENTS. 



Let r z= resistance of first line 

r / = resistance of second line 
r„ = resistance of earth. 

First connect the far end of r and r, together, and get the total resistance 
R ; connect r and r /t , and measure the resistance R, ; connect r y and r ln and 
get total resistance R /r Then if 

rr _R + R / +R // 





~ 




2 


r 


— 


T- 




', 


= 


T- 


-r" 


// 


=. 


T- 


-R. 



This test is particularly applicable to finding the resistance of trolley wires, 
feeders, and track. 



I]¥SUI,ATI©I¥ RESI§T-OCE OF XIECTRIC CIR- 
CUITS Il¥ III' I l.l>I\«*S. 

In the United States it is quite common to specify that the entire installa- 
tion when connected up shall have an insulation resistance from earth of at 
least one megohm. 

The National Code gives the following : — 

The wiring of any building must test free from grounds ; i.e., each main 
supply line and every branch circuit should have an insulation resistance of 
at least 100,000 ohms, and the whole installation should have an insulation 
resistance between conductors and between all conductors and the ground 
(not including attachments, sockets, receptacles, etc.) of not less than the 
following : — 

Up to 5 amperes . . 4,000,000. Up to 200 amperes . . 100,000. 

Up to 10 amperes . . 2,000,000. Up to 400 amperes . . 50,000. 

Up to 25 amperes . . 800,000. Up to 800 amperes . . 25,000. 

Up to 50 amperes . . 400,000. Up to 1,600 amperes . . 12,500. 

Up to 100 amperes . . 200,000. 

All cut-outs and safety devices in place in the above. 

Where lamp-sockets, receptacles, and electroliers, etc., are connected, 
one-half of the above will be required. 
Professor Jamison's rule is : — 

Resistance from earth = 100,000 X ? — : — '~r\ • 

number of lamps 

Kempe's rule is : — 

75 



Resistance in megohms 



number of lamps 
A rule for use in the U. S. Navy is : — 

E M F 

Resistance = 300,000 x , ' 1 ' , ,. • 

number of outlets 

Institution of Electrical Engineers' rule is : — 

E _ 7900 X E.M.F. 
number of lamps 

Phoenix Fire Office rule for circuits of 200 volts is that 

The least R= ™ ****** , 
number of lamps 

Twenty-five English insurance companies have a rule that the leakage 
from a circuit shall not exceed ^355 part of the total working current. 



MEASUREMENT OF ELECTROMOTIVE FORCE. 



45 



Below is a table giving the approximate insulation allowable for circuits 
having different loads of lamps. 
For a circuit having — 

25 lamps, insulation should exceed . . 500,000 ohms. 

50 lamps, insulation should exceed . . 250,000 ohms. 

100 lamps, insulation should exceed . . 125,000 ohms. 

500 lamps, insulation should exceed . . 25,000 ohms. 

1000 lamps, insulation should exceed . . 12,000 ohms. 

All insulation tests of lighting circuits should be made with the working 
current. (See page 58, voltmeter test.) 

In the following table Uppenborn shows the importance of testing with 
the working voltage. 

Table I. shows the resistance between the terminals of a slate cut out. 

Table II. shows the resistance between two cotton-covered wires twisted. 



I. 


II. 


Volts. 


Megohms. 


Volts. 


Megohms. 


5 
10 
13.6 

27.2 


68 
53 
45 
24 


5 
10 
16.9 

27.2 


281 
188 
184 
121 



MEASUREMENT OE ELECTROMOTIVE eorce. 

Of Batteries. — This can usually be measured near enough for all 
practical purposes by Weston or other high-class low-reading voltmeters 
(see voltmeter tests) ; but if greater accuracy be wanted, it can be obtained 
by comparing with a standard cell by the following method : — 

Eord Ma.yleigvh's Compensation Method. — In the following 
diagram let B and B 1 be two 10,000-ohm 
rheostats, B be the battery of larger E.M.F. 
than either of the cells to be compared, B x be 
one of the cells under test, G be a sensitive 
galvanometer, HB be a high resistance to 
protect the standard cell, and k be a key. 
Obtain a balance, so that the galvanometer 
shows no deflection on closing the key k, by 
transferring resistance from one box to the 
other, being careful to keep the sum of the 
resistances in the boxes equal to 10,000 ohms. 
Observe the resistance in B and call it B ± . 
Repeat with the other cell B 2 , and call the 
resistance B 2 . Then the E.M.F.'s of the two cells 

E 1 :E 2 = B 1 : B 2 . 

Electrometer Method. — Connect the cell whose E.M.F. it is desired 
to measure to the terminals of a quadrant electrometer, and note the deflec- 
tion d. Then substitute the standard cell for the first cell, and note the 
deflection d ± . 

e = the E.M.F. of the cell to be measured, 
e x = the E.M.F. of the standard, 
d t :d ::e 1 :e, 




Then, if 
and 



and 



Wheatstone's Method. — Connect the cell or battery to be compared 
in circuit with a galvanometer and high resistance r, and note the deflection 
d ; then add another high resistance r x (about equal to r), and note the de- 



46 



MEASUREMENTS. 



flection d,. Next, connect the cell with which the first is to be compared in 
circuit with the galvanometer, and connect in resistance until the gal- 
vanometer deflection is the same as d ; then add further resistance until 
the galvanometer deflection is the same as d r ; then, if e = the E.M.F. of the 
first cell, and E •=. the E.M.F. of the cell with which it is compared, 



and 



Il::e:E, 



MEASUBOG CAPACITY. 



Arrangement of Condensers. In Parallel. — Join like poles 

of the several condensers together as 
in the figure ; then, the joint capacity 
of the set is equal to the sum of the 
several capacities. 
Total capacity = c + c, + c„ -\- c //r 
Condensers in Series. — Join 
the unlike poles as if connecting up 
battery cells in series as in Fig. 21, 
then the joint capacity of all is the 



III 



Fig. 20. 




reciprocal of the sum of the reciprocals of the several capacities. 

Capacity C= — • 

±. + - + - + J_ 
o c / c„ c„, 
Capacity l»y Direct Discharge. — 

Charge a standard condenser, Fig. 22, Cs by 
a battery E for a certain time, say 30 sec- 
onds ; then discharge it through a ballistic 
galvanometer G ; note the throw d. 

Next charge the condenser to be measured, 
C x , by the same battery and for the same length of time, and discharge tbis 
p through the same galvanometer noting the throw d t ; 

! 1||( j Then Cb : C t :: d : d{. 

Cl - c d 

Thomson's Iflethod. — This method is that most gen- 
erally used for comparing capacities of condensers, cables, 
etc. 





Fig. 23. 



Earth 



B = battery, say 10 chloride of silver cells, 
R = variable resistance. 
i?, zr fixed resistance. 
G ■=. galvanometer. 
C— standard condenser. 
C, = cable or condenser to be measured. 
1, 2, 3, 4, 5 = keys. 



MEASURING CAPACITY. 



47 



Test. — Close key 1, thus joining the two resistances R and R x to earth. 
Then if Fand V-, = the potentials at the junctions of the battery with the 
resistances R and R,, 

V: V X ::R:R 1 . 

Close keys 2 and 3 simultaneously for a certain length of time, and charge 
the condenser Cand cable C\ to potentials Fand V, respectively. 

If C and Q be the respective capacities (in microfarads) of the condenser 
and cable, and Q and Q 1 the charges given to them, 

Q : (?! :: VC: V r C x . 

Release keys 2 and 3, then close key 4 for a fixed time, to allow the charges 
of condenser and cable to mix, then if Q is not = Q x when the key 5 is closed 
cutting in the galvanometer, there is a deflection. Change the ratio of R to 
R x until on trial there is no deflection. 

Then VC= V,C t 

or V,: V:: C : C t 

but we found V 1 : V::R 1 :R 

or R 1 :R::C:C 1 

7? 

and Cj = — C microfarads. 

M t 

Bridge Method. — For comparing the capacities of two condensers, 
Ca and C, which are approximately the same, connect as in Fig. 24 through 
two rather high inductionless resistances 
R t and R 2 to the key k which makes and 
breaks contacts at each end. E is a bat- 
tery. A galvanometer is inserted between 
the ends of the condensers where they 
join the resistances. Adjust the resist- 
ances so that no deflection results when 
the key is manipulated. 

R t Fig. 24. 

C— Ca-p-. 




Then 



Intermittent Current Method. — If a tuning fork, making n com- 
plete vibrations per second, and provided with a stylus, be connected as in 
Fig. 25, it will charge the condenser to the voltage of the battery E, and then 
discharge it through the galvanometer Q, n times 
per second. The effect on the galvanometer will 
be the same as though a constant current of 
strength, nEC, were flowing through it, where C is 
the capacity of the condenser. To determine the 
value of this current, connect the battery directly 
to the galvanometer through a total resistance R, 
so adjusted as to give the same deflection as 
before. 



& 



■=!_. 



Fig. 25. 



Then 



nEC — 



E 



n~R 



Coefficient of Self-Induction lofa Coil or Circuit. — The 

coefficient of self-induction of a coil or circuit is the equivalent in volts that 
would be produced in that coil or circuit by a rate of change of current 
equivalent to a uniform change of one ampere of current per second. It is 
numerically equal to the number of lines of force linked with the circuit 
per unit current in it. 

For example, if we have a coil of 150 turns of wire carrying 2 amperes and 
producing 200,000 lines of force, or 200 kilogausses, then one ampere would 
produce 100,000 lines ; and if it took the current one second to die out when 
the circuit was opened, then each turn would cut 100,000 lines in that time, 
and 150 turns would be equivalent to 1 turn cutting 15,000,000 lines. 1 volt 
= 10 8 lines cut by one coil ; therefore 



15,000,000 
100,000,000 



= .15 volts, or .15 henry — L. 



48 



MEASUREMENTS. 



KEAIVBEHESriS OF COEFFICIEHfTi OF INRUC- 

TIOH. 

Determination of the coefficients of inductance may be made with a 
Wheatstone's bridge, condenser, and variable non- 
inductive resistance ; connect up as follows : — 

In the cut let A and B be equal constant arms of 
the bridge ; R, the variable arm ; r, a variable non- 
inductive resistance in series with the inductive 
resistance, Ind. R, to be measured, and the ohmic 
resistance of which is R x , C being a condenser 
placed as a shunt around the two resistances. 
The resistance r is employed to enable one to use 
a condenser C of practicable size. Adjust C, r, 
and R, until there is no deflection of the galva- 
nometer when the battery circuit is opened ; 
then L=C(r + R^. 




Fig. 26. 



Another Method : — 

Let r = resistance of article to be measured, 
L = coefficient of self-induction of article, 
R — resistance = to r, 
C — capacity of a condenser in microfarads. 

Then proceed as follows : — 

1st. Balance for constant currents by adjusting r lf 
both k and k x being closed. 

2d. After closing the galvanometer key k lf close 
key k, and note the throw 1 in the ballistic galva- 
nometer. 

3d. Substitute in the bridge, for the article whose 
inductance is being measured, the condenser C 
shunted by the resistance Rz=.r. 

4th. Repeat the operation 2, and note the galva- 
nometer throw 2 . 




Fig. 27. 



Then 



L = O 2 



1,000,000 henrys. 




To Compare Two Coefficients of Self- 
induction. — Let the connections be made as in 
the cut, the two coefficients of self-induction being 
x and y in the arms A and B. 

Balance the bridge so there is no movement of the 
galvanometer needle, the key k being closed, when 
k t is opened or closed suddenly. 

Then, if the total resistance of the arm A, includ- 
ing the coil x be A, and the resistance of the arm B 
is B, including the coil y, the coefficient of the coil 
x and that of the coil y are such that 

, x a A 

we have - = •=- = -5 . 

y b B 



MEASUREMENT OF iEIF-IUfDUCTAHTCE WITH AN 

ALTERNATING CURRENT OF KNOWN 

FREQUENCY. 

For this test is needed a high resistance or electrostatic alternating cur- 
rent voltmeter, a direct current ammeter, and a non-inductive resistance. 

Connect as in Fig. 29, where i?, is an inductive resistance to be measured, 
and S a switch for short-circuiting the ammeter ; the A. C. dynamo of fre- 
quency n is so arranged that its terminals may be disconnected, and a 
battery be substituted therefore. 

With the connections as in Fig. 29, close the switch S, and take the drop 
with the voltmeter from a to b and the drop from ato C; then disconnect 



MEASUREMENT OF MUTUAL INDUCTANCE. 



49 



the A. C. dynamo, and connect the battery B ; open the switch s, and vary 
the continuous current until the drop from a to Cis the same as with the 
alternating current, both measurements being made with the same volt- 
meter ; then note the current shown by the ammeter, and measure the drop 




Fig. 29. 



from a to b with the voltmeter. Call the drop across R t from a to b, with 
alternating current, E, and the same with continuous current, E ± , and the 
reading of the ammeter with the latter, /. 



Then 



L — 



VE 2 — E? 



2irnl 

If the resistance B t be known, and the ammeter be suitable for use with 
alternating currents, the switch and non-inductive resistance may be dis- 

-A 2 



pensed with. "We then have L ■=. -±- , where I x is the value of the al- 
ternating current. 

Note. — The resistance of the voltmeter must be high enough to render 
its current negligible as compared with that through the resistance R x . 



MJEASlTMEltlliWar OJP MrTUAI lUTDTICTAUrCE. 

,. Let jl/=rthe mutual inductance between 

two coils, 
L = the self -inductance of one coil, 
L/ = the self -inductance of the other 

coil, 
L u = the self-inductance of both coils 
connected in series, 
Let L NI = the self -inductance of both coils 
connected in opposition to each 
other. 
Then, since L„ = L + L x + 2 M 
and L /// = L + L / — 2M 

„ L^ — Lj,, 
M=^ . 

Another M etltoil with battery is as 
follows : connect as in Fig. 30 where A and 
D are the two coils whose mutual induc- 
tance, M x , is required. R and R x are two 
non-inductive resistances, and C is a con- 




FiG. 30. 



50 



MEASUREMENTS. 



denser placed in shunt to R -\- i?,. Closing and opening the key k produces 
deflections of the galvanometer G by the mutual induction of the coils and 
proportional to M — CRR V Varying G gives different deflections ii 
d being the first deflection and d t a second deflection, 

CRR 1 _M— C 1 RR l 



in which, 



M 



d ~ dt ' 

d being the second value of the capacity of the condenser. 
Then M = CRR X when d is reduced to zero. 



mea§vri^g the odtctahtce oe aerial 

In the following figure a line is shown with a load of lamps or other trans- 
lating devices, although for the purpose of getting the line inductance 

alone, it would most likely be 
closed on itself. 

Connect up for a Wheat- 
stone's bridge method as 
shown in the cut ; close the 
key, and manipulate the slider 
p until a balance is obtained ; 
then vary the capacity of the 
condenser C until there is no 
movement of the needle when 
the battery circuit is broken 
with the key. 

Then, disregarding line ca- 
pacity, the inductance is 

L — cr 2 , 
and, if C = capacity of the 




line, and R be the resistance of the same, 
then L=zcr 2 4- i 



CR-. 



MEASrREXEITl OE MUTrAL IjJTDUCTA]¥CE OF 
AERIAI LIJVEi. 

To measure the mutual inductance of a pair of parallel lines, connect up 
as in the cut below. Earth both ends of each line separately, and, to avoid 
trouble from earth currents, put a small battery in secondary line with ad- 
justable shunt as shown. Adjust R and C until there is no movement of 



BATTERY 




EARTH 



PRIMARY LINE 



EARTH 



SECONDARY LINE 



' EARTH 



the galvanometer needle, when the circuit of the battery is opened with the 
key ; then, if 

R = the resistance of the rheostat 7? as finally arranged, 
R t = the resistance of secondary line, 
C = the capacity of the condenser as finally arranged, 
and M= mutual inductance, 

M— CRR X . 



MEASUREMENT OF POWER IN A. C. CIRCUITS. 



51 



MEA§URE1[E^T OF POWER I]¥ AIiTEIt]tfATII¥G 
CVRREnri CIRCHTS. 

In circuits carrying alternating currents, and having an inductance in 
some part of their length, either in the shape of motors or other inductive 
load, as unloaded transformers, and the self-induction of the wires them- 
selves, the ordinary methods of measurement of the power or watts con- 
veyed are not available, as the current is seldom exactly in phase with the 
E.M.E., and therefore the value of the current multiplied by the E.M.F. will 
not be the true watts of the circuit. 

In all alternating circuits the power, at any instant of time, is equal to 
the product of the instantaneous values of the current and voltage at that 
time. If the current be in phase with the voltage, each will have zero values 
at the same instant of time, and will have maximum positive and maximum 
negative values simultaneously. Inasmuch as the product of two negative 
quantities is a positive quantity, the power of the circuit, with no phase dif- 
ference, is made up of positive pulsations varying in magnitude from to 
a maximum. The latter is equal to the product of the maximum values of 
the current and E.M.F. If, however, the current differ by 90° in phase from 




the voltage, i.e., each having value when the other has a maximum value, 
the power will consist of a series of pidsations, first positive and then nega- 
tive, and the algebraic value of the work done, i.e., power times its dura- 
tion, woidd be equal to zero. The result is that no permanent work is done, 
and the circuit is said to have a " Power Factor " of 0. The current which 
flows is called a wattless current. If the phase difference be less than 90° 
and more than 0°, at some instants of time the product of the volts and am- 
peres will be negative, but oftener will be positive. The fractional part of 
the whole which is positive is called the power factor. It can be shown that 
the power factor is equal to the cosine of the angle of phase difference. 

Inasmuch as an ampere of alternating current is one whose maximum 
value is 1.41 amperes (V^), and a volt of alternating current is one whose 
maximum value is 1.41 volts, the following relations hold true : — 

If /= maximum value of E.M.F., 

a = maximum value of current, 
and 6 — angle of lag of current behind the E.M.F., 



then 



True Watts =^^~ X Cos 9. 



MEASUREMENTS. 



If E — E.M.F. by voltmeter : Vmean 2 , 

/= current by ammeter : Vmean 2 , 
6 = angle of lag, 
W = watts measured by watt meter, 

W 

then -= T = Cos 6 = Power factor, 

E X I ' 

or the power factor is the value by which the observed volt-amperes must 
be multiplied to give the true watts. 

If a wattmeter be without self-induction in its fine wire coils, and the 
supporting part be not subject to eddy currents, then it may be used for 
measuring the value of power in A. C. circuits ; in fact, in all full tests of 
alternating-current work it is necessary to have wattmeter, ammeter, and 
voltmeter readings. 

Three Voltmeter Method. Ayrton & Sumpner. 

This method is good where the voltage can be regulated to suit the load. 

In figure 31 let the non-inductive re- 
sistance R be placed in series with the 
load a b ; take the voltage V across Ike 
terminals of R ; V x across the load w b, 
and V 2 across both, or from a to c. 
Then the 

y 2 y 2 y 2 

True watts = — =-jr . 

The best conditions are when V = V v 
and, if R = J ohm, / 

F, 2 — V 2 . 




then 



w= v 2 2 

Three Ampere Meter Method (not recommended). 

This method, due to Fleming, can be used when it is not convenient to 
regulate the potential of load a b. 

In Fig. 35 R is a non-inductive resistance „ v 

connected in shunt to the inductive load 
a b, with the three ammeters connected as 
shown, 



Then 



True watts = — (A 2 



A 2 - A 2 ). 




Combined 



Voltmeter and 
ter Method. 



Amine- 



Fig. 35. 



This method, devised also by Fleming, is quite accurate, and enables the 
accuracy of instruments in use to be 
checked. In Fig. 36 R is a non-inductive 
resistance connected in shunt to the induc- 
tive load a b, and the voltmeter V measures 
the p. d. across x y. A and A x are ammeters 
connected as shown ; then 
R 




True watts 



(*-*-®y 



Fig. 36. 



If the voltmeter F takes an appreciable 
amount of current, it may be tested as fol- 
lows : disconnect R and Fat y, and see that A and A, arealike ; then con- 
nect R and V at y again, and disconnect the load a b. Then A x = current 
taken by R and V in multiple. 

As regards all the above mentioned tests with 3 voltmeters, ammeters, etc., 
it may be said that they were developed at a time when no good alternating 
current instruments were available. Since then a number of good A. C. 
voltmeters have been developed, and more recently the inclined coil instru- 
ments of the General Electric Co., and Schallenberger instruments of tbe 
Westinghauss Co., have placed instruments in our hands that make alternat- 
ing-current testing nearly as easy as d. c. testing. 



TESTS WITH VOLTMETER. 



53 



TE§TS WITH VOLTMETER. 

The following are a few of the more important tests for which a voltmeter 
is especially adapted, and have mostly been condensed from a very fine 
article by IT. Maschke, Ph.D. published in the Electrical World in April, 
1892. 

The scales of the better known portable instruments of to-day read in gen- 
eral from to 150 volts, or from to 750 volts, and in special instruments the 
two scales are combined, so that by connecting one wire to one or the other 
of two binding posts either scale is available. Instruments for battery use 
read from to 15 volts with a second scale reading as low as -^ g , or 1.5 volts. 
Millivoltmeters reading from to ■£$, or to jj-f,, etc., with divisions capable 
of being read as low as ttocjoo vou % are also obtainable. 

None of the refined laboratory methods will be given here, as the reader is 
referred to the text-books for such tests. 



EIECTROmOTIIE FORCE OF RATTERIE§. 

The positive post of voltmeters is 
usually at the right, and marked +• 
In a battery the zinc is commonly neg- 
ative, and should therefore be con- 
nected to the left or negative binding 
post. 

For single cells or a small number, 
a low-reading voltmeter, say one read- 
ing to 15 volts, Avill be used, the con- 
nections being as per diagrams. 





ELECIROMOIRE FORCE 
OF »Y]¥AJ¥IOS. 



Fig. 38. 



For voltage within range of the instrument available for the purpose, it is 
only necessary to connect one terminal of the voltmeter to a brush of one 
polarity, and the other terminal to a brush of the opposite polarity, and 
read direct from the scale of the instrument. As continuous current volt- 
meters usually deflect forward or back according to which pole is connected, 
it is necessary sometimes to reverse the lead wires, in which case the polar- 
ity of the dynamo is also determined. Of course the voltage across any cir- 
cuit may be taken in the same way, or the dynamo voltage may be taken at 
the switchboard, in Avhich case the drop in the leads sometimes enters into 
the calculations. Following are diagrams of the connections to bipolar and 
multipolar dynamos : — 





Fig. 40. 



In the case of arc dynamos or other machines giving high voltage, it is 
necessary to provide a multiplier in order to make use of the ordinary in- 
strument; and the following is the rule for determining the resistance 
which, when placed in series with the voltmeter, will provide the necessary 
multiplying power. 



54 



MEASUREMENTS. 



Let 



Then 



e = upper limit of instrument scale, for example 150 volts, 
E = upper limit of scale required, for example 750 volts, 
R = resistance of the voltmeter, for example 18,000 ohms, 

r = additional resistance required, in ohms. 



II 



or r = 18,000 



750 — 150 



The multiplying power 



150 
E 



= 72,000 ohms. 
750 „ 



Should the exact resistance not he available, then with any available 
resistance r x the regular scale readings must be multiplied by ( ~ -\- 1 ) . 



IMPOBTAICE OF IffB^M REilSTAl'CE 

VOSyFMFXERS. 



FOR 



r^v 



Xuu- 



Fig. 41. 



It is highly important, as reducing the error in measurement, that the in- 
ternal resistance of a voltmeter be as high as practicable, as is shown in the 
following example : — 

Let E in the figure be a dynamo, battery, or other 
source of electric energy, sending current through the 
resistance r ; and vm. be a voltmeter indicating the 
pressure in volts between the terminals A and B. Be- 
fore the vm. is connected to the terminals A and B there 
will be a certain difference of potential, which will be 
less when the voltmeter is connected, owing to the les- 
sening of the total resistance between the two points ; 
if the resistance of the vm. be high, this difference will 
be very small, and the higher it is the less the error. 
Following are the formulas and computations for de- 
termining the error. 

In the above figure let E be the E.M.F. of the dynamo, 
r the resistance of the circuit as shown between A and 
B, and r x be the resistance of the leads A and B plus 
that of the dynamo, and let R be the resistance of the voltmeter ; then before 
the vm. is connected the difference between A and B will be 

T 

e - —. — X E, 
r +r x 

and after connecting the voltmeter it will be 

e RXr X E 

1 R X r -f r x r x -\- r L x R 

The difference between the two results e and e x is then 

1 r x r, 

R r -j- r 1 

and this difference will be smaller the greater the resistance R of the vm. is. 

Example : — 
Let E = 10 \tdts 

r = 10 olims 
r x = '2 ohms 
R = 500 ohms 



then 



and 



500 X 10 



500 X 10 + 10 X 2 + 2 X 500 



1 10 v 2 

- Ci = ^ X ttt^t, X 10 = .0333. 



X 10 = 8.3056, 



500 ' N 10 + 2 
If R be made 1000 ohms, then 

1000 X 10 



and 



1000 X 10 + 10 X 2 + 2 X 1000 
1 10 X 2 



X 10: 



.32, 



1000 X 10 + 2 



Xl0= .0166. 



COMPARISON OF E.M.F. OF BATTERIES. 



55 



or just one half of the error ; it may be said that the error is therefore in 
inverse proportion to the resistance of the vm. 
If the error of measurement is not to exceed a stated per cent p, then r 

and r x must be such that J 



is smaller than ^ ^ ohms. 



If the circuit is not closed by a resistance r, then with vm. connected 
between A and B 

and the error between the true value and that shown on the vm. is 

and this error decreases in inverse proportion to the increase of the ratio 
between R and the internal resistance of the current generator r x . 
If the error is not to exceed p per cent, then the internal resistance r t must 



be 



than ohms. 



The E.M.F. of high-resistance cells cannot be correctly measured by the 
above method, even with voltmeters of relatively higli resistance, but it is 
better done by one of the methods mentioned below. 

COMPAKIiOJIf OF E.M.F. ©IF BATTERIES. 

l^lieatstone's Method. — To compare E.M.F. of two batteries A and 
X, with low-reading voltmeters, let E be the E.M.F. of A ; and E-. the E.M.F. 
of X 




Fig. 42. 



First connect battery A in series with the voltmeter and a resistance r, 
switch B being closed, and note the deflection V; then open the switch B, 
and throw in the resistance r x , and note the deflection V x . Now connect bat- 
tery Xin place of A. and close the switch B, and vary the resistance r until 
the same deflection Vol voltmeter is obtained and call the new resistance r 2 ; 
next open the switch B, or otherwise add to the resistance r 2 until the deflec- 
tion V x of the voltmeter is produced ; call this added, resistance r 3 , then 
E :E 1 ::r l :r,. 

If E be smaller than E^, the voltmeter resistance R may be taken as r, and 
it is better to have r x about twice as large as the combined resistance of r 
and the resistance of A. 

It is not necessary that the internal resistance of the cells be small as 
compared with R. 

J*o§-g-eia«lorff's Method Modified Iby Clark. 

To Compare the E.M.F. of a battery cell or element with a standard cell. 
Let S be a standard cell, 

T be a cell for comparison with the standard, 

B~be a, battery of higher E.M.F. than either of the above elements. 
A resistance r is joined in series with the battery B and a slide wire A D. 
A millivoltmeter is connected as shown, both its terminals being connected 
to the like poles of the battery B and the Standard S. 



MEASUREMENTS. 




Fig. 43. 



Move the contact C along the wire until the pointer of the instrument 
stands at zero, and let r 1 be the resistance of A C. 

Throw the switch b so as to cut out the standard S, and cut in the cell T ; 
now slide the contact C\ along the wire until the pointer again stands at 
zero, and call the resistance of A C x r 2 , 

Then the E.M.Fs. of the two cells 

T: S ::r 2 :r v 

If a meter bridge or other scaled wire be used in place of A D, the results 
may be read directly in volts by arranging the resistance r so that with the 
pointer at zero the contact C is at the point 144 on the wire scale, or at 100 
times the E.M.F. of the standard S, which may be supposed to be a Clark 
cell. All other readings will in this case be in hundredths of volts ; and 
should the location of C x be at 175 on the scale when the pointer is at zero 
on the voltmeter, then the E.M.F. of the cell, being compared, will be 1.75 
volts. 

*1R 1*1 111 Y4~ CrilREXT §TRE1«TH WITH A. 
VOLTMETER. 



If the resistance of a part of an electric circuit be known, taking the drop 
in potential around such resistance will determine the current flowing by 

ohms law viz., J= — . 
si 

In the figure let r be a known resistance be- 
tween the points A and B of the circuit, and I 
the strength of current to be determined ; then 
if the voltmeter, connected as shown, gives a 
deflection of V volts, the current flowing in r 

V 

will be I=i — . 

r 

For the corrections to be applied in certain 
cases, see the section on Importance of High 
Resistance for Voltmeters. 

Always see that the resistance r has enough 
carrying capacity to avoid a rise of temperature 
which would change its resistance. 

If the reading is exact to — volt the meas- 
urement of current will be exact to am- 

p Xr 

peres. If r =r .5 ohm, and the readings are taken on a low-reading volt- 
meter, say ranging from to 5 volts, and that can be read to ^ha volt, then 
the possible error will be 




300 X .5 



= _ ampere. 



MEASURING RESISTANCE WITH A VOLTMETER. 57 
If r be made equal to 1 ohm, then the volts read also mean amperes. 

Measurement of "Very Heavy Currents with a Milli- 
voltmeter. 

For this purpose the method outlined above is most generally used with 
the substitution of a millivoltmeter for the voltmeter. 

"Where portable instruments are used, there must be a calibrated shunt 
for the millivoltmeter, the shunt being made up of a metal that does not 
vary in resistance with change of temperature, and which is placed in series 
in the circuit, the millivoltmeter simply giving the drop around this shunt, 
its scale being graduated in amperes. 

For switchboard instruments the method is the same, being varied some- 
times by using as a shunt a measured part of a conductor or bus bar in place 
of a special resistance. 

MEASURING BXSIilAITCE WITH A TOITMETER. 

General Methods. — In the figure, let X = the unknown resistance 
that is to be measured, r — a known resistance, E, the dynamo or other 
steady source of E.M.F. 

When connected as shown in the figure, let 
the voltmeter reading be V; then connect the 
voltmeter terminals to r in the same manner 
and let the reading be V 1 ; then 

X:r:: V: 
and 

If, for instance, r = 2 ohms and V = 3 volts 
and V x — 4 volts then 

I= 2 4 3 = 1.5ohms. 
4 

If readings can be made to T -J- s volt, the error of resistance measurement 
will then be 



"""N®^ 




— vwww- 


■ AA/W- 




m 








Fn 


G. 


45. 




100Xxkr( T 4--jL) 



per cent. 



and for the above example would be 

1 (i + J) =± 0.58%. 
Should there be a considerable difference between the magnitudes of the 
two resistances X and r, it might be better to read the drop across one of 
them from one scale, and to read the drop across the other on a lower scale. 

Resistance Measurement with "Voltmeter and Ammeter. 

The most common modification of the above method is to insert an am- 

V 
meter in place of the resistance r in the last figure, in which case X=-=. 

where lis the current flowing in amperes as read from the ammeter. 

If the readings of the voltmeter be correct to t a<j and the ammeter read- 
ings be correct to the same degree, the possible error becomes : 

1Wx (iWT + ibl7) =percent - 

Measurement of Very Small Resistances with a Millivolt- 
meter and Ammeter. 

By using a millivoltmeter in connection with an ammeter, very small re- 
sistances, such as that of bars of copper, armature resistance, etc., can be 
accurately measured. 



58 



MEASUREMENTS. 





n 


M.Vm, 
V 




(a 






V 






' 


X 


() 










^\ . 


© 


Am. 


y 


l_ 


1 





Pig. 46. 

In order to have a reasonable degree of accuracy in measuring resistance 
by the "drop" method, as this is called, it is necessary that as heavy cur- 
rents as may be available be used. Then, if E be the dynamo or other source 
of steady E.M.F., Xbe the required resistance of a portion of the bar, V be 
the drop in potential between the points a and b, and / be the current flow- 
ing in the circuit as indicated by the ammeter, then 

The applications of this method are endless, and but a few, to which it is 
especially adapted, need be mentioned here. They are the resistance of 
armatures, the drop being taken from opposite commutator bars and not 
from the brush-holders, as then the brush-contact resistance is taken in ; the 
resistance of station instruments and all switchboard appliances, such as 
the resistance of switch contacts ; the resistance of bonded joints on electric 
railway work, as described in the chapter on railway testing. 



Measurement of Hig-h Resistances. 

With the ordinary voltmeter of high internal resistance, let R be the re- 
sistance of the voltmeter, X be the resistance to be measured. Connect them 
up in series with some source of electro- 
motive force as in the following figure. 

Close the switch b, and read the voltage 
V with the resistance of the voltmeter 
alone in circuit ; then open the switch, 
thus cutting in the resistance X, and take 
another reading of the voltmeter, V,. 

Then X=s(¥—l\. 

If the readings of the voltmeter be cor- 
rect to Jj of a volt the error of the above 

result will be — I -=-! — —■ 1 




per cent. 



MEASURING THE l\S|LlTIO> OF LIGHTING 
A]¥» POWER CIRCUITS WITH A A OLTMJT1H 

For rough measurements, where the exact insulation resistance is not re- 
quired, but it is wished to determine if such resistance exceeds some stated 
figure or rate, then the method above given will do, when applied as fol- 
lows : — 
Let X= insulation resistance to ground as in figure, 

X, =. insulation resistance to ground of opposite lead, 
R = resistance of voltmeter, 
F = potential of dynamo E, 

V, = reading of voltmeter, as connected in figure, 
V„ = reading of voltmeter, when connected to opposite lead. 






MEASURING LINE INSULATION. 



59 




Ground 



Then 



and 



X = R 



X, = R 



The above formula can be modified to give results more nearly correct by 
taking into account the fact that the path through the resistance R of the 
voltmeter is in parallel with tbe leak to ground on the side to which it is 
connected as shown in the following figure : — 




In this case the voltage V of the circuit will not only send current through 
the lamps, but through the leaks e f to ground, and through the ground to 
d and c, thence through d to b, and c to a, these two last paths being in par- 
allel, therefore having less resistance than if one alone was used ; thus if r 
be the resistance of the ground leak b d, and r t be the resistance of the leak 
e f, and R be the resistance of the voltmeter, then the total resistance by 
way of the ground, between the conductors, would be 
R Xr 

and if V= voltage of the circuit, 

v = reading of voltmeter from a to c, 
v, = reading of voltmeter from g to c. 

Then r = Bf r - (V + V ^ 



and 



r l = R 



The sum of the resistance r 



Vj ) 

Pi will be — R 



'( t . + r/ )(r-(p + p/)v 



Insulation Resistance of Arc Circuits. 

As arc lamps are by much the larger extent run in series, the insulation 
resistance of their circuits is found in a manner similar to that for multiple 



60 



MEASUREMENTS. 



circuits, but the formula differs a little. Let the following figure be a 
typical arc circuit, with a partial ground at c. 

First find the total voltage V between a and b of the circuit. This can 
most handily be done with a voltmeter having a high resistance in a sepa- 
rate box and so calibrated with the voltmeter as to multiply its readings by 




Fig. 50. 

some convenient number. For convenience in locating the ground, get the 
average volts per lamp by dividing the total volts V by the number of lamps 
on the circuit ; the writer has found 48 volts to be a good average for tbe 
ordinary 10 ampere lamp. With the 16 lamps shown in the above figure, V 
would probably be about 768 volts. 

Next take a voltmeter reading from each end of the circuit to ground. 
Call the reading from a to ground v, and from b to ground v n R being the 
resistance of voltmeter as before, and r the insulation resistance required. 

V—(v -\-vj)\ 



Then 



U 



v-\-v, 



and the location of the ground, provided there be but one, and the general 
insulation of the circuit be good, will be found closely proportional to the 
leadings v and v, ; in the above figure say we find the voltmeter reading 
from a to ground to be 28, and from b to ground to be 36 ; then the distance 
of the ground c from the two ends of the circuit will be in proportion to the 
readings 28 and 36 respectively. 

There being 16 lamps on the circuit, the number of lamps between a and c 
would be 28 -^ (28 + 36) = f f of 16 = 7, and from Hoc would be 36 -f 
(28 + 36) = || of 16 = 9 ; that is, the ground would most likely be found be- 
tween the seventh and eighth lamps, counting from a. 

Insulation across a Double Pole Fuse Block or Other 

Similar Device where Both Terminals are on 

the Same Base. 



Let ffbe fuses in place on a base, 
"F= potential of circuit, 
R ■=. resistance of voltmeter, 
v = reading of voltmeter, 
required the resistance r across the base 
a a, to b 6. . 

V — v E 

Then r — R . 



JTIE 1*1 18 i:\Ch THE IWSU- 
I.ATIOIV OF DYISAMOS. 




Fig. 51. 



The same formula as that used for measuring high resistances (see Fig. 
47) applies equally well to determining the insulation of dynamo conductors 
from the iron body of the machine 



MEASURING INSULATION RESISTANCE. 



61 




Fig. 52. 



Connect, as in Fig. No. 52, all symbols having the same meaning as 
before. 
Let r = insulation resistance of dynamo, then 



■=,( 



M£A§tRI]¥« THE IHTSUXATIOtf MJSISTABfCB OF 
MOTORS. 

Where motors are connected to isolated plant circuits with known high 
insulation, the formula used for insulation of dynamos applies ; but where 
the motors are connected to public circuits of questionable insulation it is 
necessary to first determine the circuit insulation, which can be done by 
using the connections shown in Fig. 48. Fig. 53 shows the connections to 
motor for determining its insulation by current from an operating circuit. 




Here, as before, 
V .\ 



Fig. 53. 
the insulation r of the 



total connected devices — 



*u 



If r = total resistance of circuit and motor in multiple to ground, and r, 
is the insulation of the circuit from ground, then X, the insulation of the 



motor will be 



X= 



MEASCREIHEIirT OF THE RFSISXAWCE OF THE 
HUMAIV BODY. 

The jars j j of the following figure (No. 54) are filled with a weak solution 
of caustic potash ; the person whose resistance is to be measured places his 
hands in the jars, if the measurement is to be made from hand to hand, or 



62 



MEASURE MENTS. 



makes an equally good connection with any other desirable portion of the 
body. 

First take a reading of tbe voltmeter with the switch K closed ; then 
have the subject plunge his hands 
into the jars, open the switch A, 
and take another reading of the 
voltmeter. The resistance r of the 
subject will be 



= <-)• 



in which R is the resistance of 
voltmeter, 

V is the reading of volt- 
meter alone, 

Vj is the reading of volt- 
meter with switch A 
open and the subject 
in series with volt- 
meter. 




MEA8UREME]¥T OF THE IHXEItlfAIi REilSTAlTCE 
OE A BATTERY. 



Fig. 55. 



In. the following figure (No. 55), let E be the cell or battery whose resistance 

is to be measured, K be a switch, and 
r a suitable resistance. 
liet V = the reading of voltmeter 
with the key, A, open 
(this is the E.M .F. of the 
battery), and 
V, = the reading of voltmeter 
with key, A, closed (this 
is the drop across the re- 
sistance r), 
Then the battery resistance 



«/ 


4 






\ 


Vm. 


<^1 




£ : 


Xr 


f 


:\H 




_s 







r, = rx 



ohms. 



§IE9IE^§.EROEIICH METHOD. 

In the following figure (No. 56), let E be the cell or battery to be measured, 
K a switch for closing resistance r to 
B or c ; r, r^ and r 2 be suitable resis- 
tances connected as" shown. The volt- 
meter should of course be a low-reading 
one. Close by the key A, A and c, and 
read the voltmeter ; next close by the 
key A, A and B, and read the volt- 
meter ; then adjust r 2 until the volt- 
meter reading is the "same for either 
position of the key A, and r 2 is then 
equal to the resistance of the battery A. 

In most cases it is best to connect 
some known resistance in series with the cell, so that the current may not 
be excessive and harm the cell ; if this be done, of course it is necessary to 
deduct this known resistance from the final reading r 2 . 




CO^TBTJCTIVITY WITH A MIILIVOLTMETER. 

This is a quick and convenient method of roughly comparing the conduc- 
tivity of a sample of metal with that of a standard piece. 

In Fig. 57, R is a standard bar of copper of 100% conductivity at 70° F. ; 
this bar may be of convenient length for use in the clamps, but of known 



CONDUCTIVITY WITH A MILLIVOLTMETER. 



63 



cross section. X is the piece of metal of unknown conductivity, but of the 
same cross section as the standard. E is a source of steady current, and if 
a storage battery is available it is much the better for the purpose. M is a 
millivoitmeter with the contact device d. The distance apart of the two 
points may be anything, so long as it remains unaltered and will go between 
the clamps on either of the bars. 

Now with the current flowing through the two bars in series the fall of 
potential between two points the same distance apart and on the same flow- 




FlG. 57. 



line will, on either bar, be in proportion to the resistance, or in inverse pro. 

portion to the conductivity ; therefore by placing the points of d on the bars 

in succession, the readings of the millivoitmeter will give the ratio of the 

conductivities of the two pieces. 

For example : — 

if the reading from B = 200 millivolts, 

and the reading from X = 205 millivolts, 

then the percentage conductivity of X as compared with R is 

205 : 200 : : 100 : conductivity of X, 

200 X 100 nr7 _„ 
or ___ = 97 .5 % . 



MAGNETIC PROPERTIES OP IRON. 

With a given excitation the flux $ or flux-density (E of an electromagnet 
will depend upon the quality of the iron or steel of the core, and is usually 
rated as compared with air. 

If a solenoid of wire be traversed with a current, a certain number of 
magnetic lines of force, JC> will De developed per square centimetre of the 
core of air. Now, if a core of iron be thrust into the coil, taking the place of 
the air, many more lines of force will flow ; and at the centre of the solenoid 
these will be equal to (^ lines per square centimetre. 

As iron or steel varies considerably as to the number of lines per square 
centimetre (g which it will allow to traverse its body with a given excitation, 
its conductivity towards lines of force, which is called its permeability, is 
numerically represented by the ratio of the flux-density when the core is 
present, to the flux-density when air alone is present. This permeability 
is represented by fx. 

The permeability ju. of soft wrought iron is greater than that of cast iron ; 
and that for mild or open-hearth annealed steel castings as now made for 
dynamos and motors is nearly, and in some cases quite, equal to the best 
soft wrought iron. 

The number of magnetic lines that can be forced through a given cross- 
section of iron depends, not only on its permeability, but upon its satura- 
tion. For instance, if but a small number of lines are flowing through the 
iron at a certain excitation, doubling the excitation will practically double 
the lines of force ; when the lines reach a certain number, increasing the 
excitation does not proportionally increase the lines of force, and an excita- 
tion may be reached after which there will be little if any increase of lines 
of force, no matter what may be the increase of excitation. 

Iron or steel for use in magnetic circuits must be tested by sample before 
any accurate calculations can be made. 



Data for (B-5C Curves. 

Average First Quality American Metal. 
(Sheldon.) 





u4 


u'B 


Cast Iron. 


Cast Steel. 


Wrought Iron 


Sheet Metal. 


JC 


Sac 

<!+S 33 
© 


© ^ j> 
111 


03 
. © 

~o 03 

do 


A © . 
S D0 " rH 

5h © GO 


03 
i © 

~ O °3 


X © . 

* as 

^ CD 03 

74.2 


03 

1 © 

_ O 03 


K © . 

•rH 03 03 


03 

1 © 

_ O 03 

be 


* © . 

5 °°" • 

•r-l OP OQ 


10 


7.95 


20.2 


4.3 


27.7 


11.5 


13.0 


83.8 


14.3 


92.2 


no 


15.90 


40.4 


5.7 


36.8 


13.8 


89.0 


14.7 


94.8 


15.6 


100.7 


30 


23.85 


60.6 


6.5 


41.9 


14.9 


96.1 


15.3 


98.6 


16.2 


104.5 


40 


31.80 


80.8 


7.1 


45.8 


15.5 


100.0 


15.7 


101.2 


16.6 


107.1 


50 


39.75 


101.0 


7.6 


49.0 


16.0 


103.2 


16.0 


103.2 


16.9 


109.0 


GO 


47.70 


121.2 


8.0 


51.6 


16.5 


106.5 


16.3 


105.2 


17.3 


111.6 


70 


55.65 


141.4 


8.4 


53.2 


16.9 


109.0 


16.5 


106.5 


17.5 


112.9 


80 


63.65 


161.6 


8.7 


56.1 


17.2 


111.0 


16.7 


107.8 


17.7 


114.1 


90 


71.60 


181.8 


9.0 


58.0 


17.4 


112.2 


16.9 


109.0 


18.0 


116.1 


100 


79.50 


202.0 


9.4 


60.6 


17.7 


114.1 


17.2 


110.9 


1S.2 


117.3 


150 


119.25 


303.0 


10.6 


68.3 


18.5 


119.2 


18.0 


116,1 


19.0 


122.7 


200 


159.0 


404.0 


11.7 


75.5 


19.2 


123.9 


18.7 


120.8 


19.6 


126.5 


J50 


198.8 


505.0 


12.4 


80.0 


19.7 


127.1 


19.2 


123.9 


20.2 


130.2 


;;oo 


238.5 


606.0 


13.2 


85.1 


20.1 


129.6 


19.7 


127.1 


20.7 


133.5 



oc 



1.258 ampere turns per cm. = .495 ampere turns per inch. 



64 



MAGNETIC PROPERTIES OF IRON. 



65 



g I 



Ct' 



1 










1 








1 


1 








l_ 










1 






























































\ 
















!\ 










1 1° 


















14 








2 
















\ 








1 








\ 








H \ 










t ' 








H \ 










I 






liU 










1 


















-\ 






— p 


-»\ \ 










\ 
















_W1 






m 


\ 








\ 






!\ 


\ 








: r 








\ 








- A 








\ 


\ 








_ _\ 










A\ 








L_ 










\\\ 








- \ 










\\\ 








_ \ 










u 








V 










\ 








\ 










\ 










\ 








\ 










V 


















V; 




•o 


9 » a 






•<J 




«- O O CO 







!IS 



< 


< 


■* 

CM 
CM 


o 


ce 
o 

CM 


o 


3 


c 
<* 


s 


c 


o 


o 
o 
■* 


* 


o 


CO 


o 


"~ 


CO 


k 


c 

CM 


s 


o 


o 


o 
c 

CM 


s 


o 


CO 


o 

CM 


8 


O 


S 


§ 



HONiauvnos bad sniaMxvwonx 



Fig. 1. Magnetic Properties of Iron. 



66 



MAGNETIC PROPERTIES OF IRON. 



In large generators, having toothed armatures and large flux densities in 
the air-gap, the flux is carried chiefly by the teeth. This results in a very 
high tooth flux density, and a correspondingly reduced permeability. The 
related values of (ft, JC, ancl M are given in the following table. These 
values are for average American sheet metal. 

Permeability at Hig-h flux Densities. 





Ampere 


Ampere 


(B 


Kilomax- 




3C 


Turns per 


Turns per 


Kilo- 


wells per 


M 




cm. Length. 


Inch Length. 


gausses. 


Square in. 




200 


159 


404 


19.8 


127 


99.0 


400 


318 


808 


21.0 


135 


52.5 


600 


477 


1212 


21.5 


138 


35.8 


800 


637 


1616 


21.8 


140 


27.3 


1000 


795 


2020 


22.0 


142 


22.0 


1200 


954 


2424 


22.3 


144 


1.8 


1400 


1113 


2828 


22.5 


145 


1.6 



METHODS OF DETERMINING THE MAGNETIC 
aVALITIEi ©E IRON AND §TEEL. 

The methods of determining the magnetic value of iron or steel for elec- 
tro-magnetic purposes are divided by Prof. S. P. Thompson into the follow- 
ing classes : Magnetometric, Balance, Ballistic, and Traction. 

The first of these methods, now no longer used to any extent, consists in 
calculating the magnetization of a core from the deflection of a magneto- 
meter needle placed at a fixed distance. 

In the Balance class, the deflection of the magnetometer needle is bal- 
anced by known forces, or the deflection due to the difference in magnetiza- 
tion of a known bar and of a test bar is taken. 

The Ballistic method is most frequently used for laboratory tests, and for 
such cases as require considerable accuracy in the results. There are really 
two ballistic methods, the Ring method and the Divided-bar method. 

In either of these methods the ballistic galvanometer is used for measur- 
ing the currents induced in a test coil, by reversing the exciting current, or 
cutting the lines of force. 

Ring- Method. — The following cut shows the arrangement of instru- 
ments for this test, as used by Prof. Rowland. The ring is made of the 
sample of iron which is to undergo test, and is uniformly wound with the 



BALLISTIC 
GALVANOMETER 




Fig. 



SWITCH 

Connections for the Ring Method. 



exciting coil or circuit, and a small exploring coil is wound over the excit- 
ing coil at one point, as shown. The terminals of the latter are connected 
to the ballistic galvanometer. 



MAGNETIC TEST METHODS. 



67 



The method of making a test is as follows : — 

The resistance, R, is adjusted to give the highest amount of exciting cur- 
rent. The reversing switch is then commutated several times with the gal- 
vanometer disconnected. After connecting the galvanometer the switch is 
suddenly reversed, and the throw of the galvanometer, due to the reversal 
of the direction of magnetic lines, is recorded. The resistance, R, is then 
adjusted for a somewhat smaller current, which is again reversed, and the 
galvanometer throw again recorded. The test is carried on with various 
exciting currents of any desired magnitude. In every case the exciting cur- 
rent and the corresponding throw of the galvanometer are noted and 
recorded. 

If i — amperes flowing in the exciting coil, 

% = number of turns of wire in exciting coil, 
I rr length in centimetres of the mean circumference of the ring, 
then the magnetizing force 



oe-- 



-for 1.257 X^-. 



If I" = length of the ring in inches, then 
3C" = -495 



IF' 



If = the throw of the galvanometer, 
K= constant of the galvanometer, 
R = resistance of the test coil and circuit, 
n 2 = number of turns in the test coil, 
a =z area of cross-section of the ring in centimetres, then 

~ 1&RK9 

04 ~~ 2 an 2 ' 

To determine K, the constant of the galvanometer, discharge a condenser 
of known capacity, which has been charged to a known voltage, through it, 
and take the reading 1 , then 



If 



c — capacity of the condenser in microfarads, 

e = volts pressure to which the condenser is charged, 



then the quantity passing through the galvanometer upon discharge in 
coulombs is Q= T JZ±- o , 
and the galvanometer constant 



1,000,000 6 1 



Divided-Bar Method. 

obtain samples in the form of 
a ring, and still more incon- 
venient to wind the coils on it, 
Hopkinson devised the di- 
vided-bar method, in which 
the sample is a long rod \" 
diameter, inserted in closely 
fitting holes in a heavy 
wrought iron yoke, as shown 
in the following cut. 

In the cut the exciting coils 
are in two parts, and receive 
current from the battery and 
through the ammeter, resist- 
ance, and reversing switch, 
as shown 



- As it is often inconvenient or impossible to 

AMMETER 
DIVISION IN 

V. TEST P^ECE- 
HANDlE 




'TO V--MEAN.CENGT.H 
„ L OF TEST. PIECE 



Fig. 3. Arrangement for Hopkinson s di- 
vided-bar method of measuring permea- 
bility. . 
The test bar is divided near the centre at the point indicated m tbe cut, 
and a small light test coil is placed over it, and so arranged with springs as 



68 



MAGNETIC PROPERTIES OF IRON. 



to be thrown clear out of the yoke when released by pulling out the loose 
end of the test bar by the handle shown. 

In operation, the exciting current is adjusted by the resistance R, the test 
bar suddenly pulled out by the handle, thus releasing the test coil and pro- 
ducing a throw of the galvanometer. As the current is not reversed, the 
induced pressure is due to i^only, and the equation for (35 is 



(B = 


_ 10» R K e 

an 2 


3C = 


_4tt 
= 10 




Where L - 


= the mean 



, and 



1.257 



i' 



the mean length of the test rod as shown in the cut. 

In using the divided-bar method, a correction must be made, for the rea- 
son that the test coil is much larger than the test rod, and a number of 
lines of force pass through the coil that do not through the rod. This cor- 
rection can easily be determined by taking a reading with a wooden test 
rod in place of the metal one. 

An examination of the cut will show that the bar and yoke can also be 
used for the method of reversals. 

The fourth or Traction class is exceedingly simple, and was devised by 
Prof. Silvanus P. Thompson. 

The following cut shows the method with sufficient clearness. A heavy 
yoke of wrought iron has a small hole in one end through which the test 
rod is pushed, through the exciting coil 
shoAvn, and against the bottom of the 
yoke, which is surfaced true and smooth, 
as is the end of the test rod. 

In operation, the exciting current is ad- 
justed by the resistance R, and the spring 
balance is then pulled until the sample or 
test rod separates from the yoke, at which 
time the pull in pounds necessary to pull 
them .apart is read. Then 




= 1,317 X 



s/ 



■oe- 



Where P — pull in pounds as shown on 
the balance, 

A = area of contact of the rod 
and yoke in square inches. 

JC is found as in the Hopkinson method 
preceding this. 

Following is a description of a practical adaptation of the permeameter to 
shop-work as used in the factory of the Westinghouse Electric and Manu- 
facturing Co. at Pittsburgh, Pa. 



Fig. 4. S. P. Thompson's per- 
meameter. 



Xlie Permeameter, as used by tlie Westing-house Electric 

and IMfgr. Co. 

Design and Description prepared by Mr. C. E. Skinner. 



A method of measuring the permeability of iron and steel known as the 
" Permeameter Method " was devised by Prof. Silvanus P. Thompson, and is 
based on the law of traction as enunciated by Clerk Maxwell. According to 
this law the pull required to break any number of lines of force varies as the 
square of the number of lines broken. (A complete discussion of the theory 
of the permeameter, with the derivation of the proper formula for calculating 
the results from the measurements will be found in the " Electro Magnet," 
by Prof. S. P. Thompson.) 

A permeameter which has been in use for several years in the laboratory 
of the Westinghouse Electric and Manufacturing Company, and which has 
given excellent satisfaction, is shown in the accompanying drawings. The 



THE PERMEAMETER. 69 

yoke, A, consists of a piece of soft iron 1" x %\" x 2J", with a rectangular 
opening in the centre 1\" x 4". The sample, X, to he tested is §" in diam- 
eter and 1\ H long, and is introduced into the opening through a § " hole in the 
yoke, as shown in the drawing. The 1 est sample is finished very accurately to 
f " in diameter, so that it makes a very close fit in the hole in the yoke. The 
lower end of the opening in the yoke and the lower end of the sample are 
accurately faced so as to make a perfect joint. The upper end of the sam- 
ple is tapped to receive a \" screw %" long, twenty threads per inch, hy 
means of which a spring balance is attached to it. The magnetizing coil, C, 
is wound on a brass spool, S, 4" long, with the end flanges turned up so that 
it may be fastened to the yoke by means of the screws. The axis of the coil 
coincides with the axis of the yoke and opening. The coil has flexible leads, 
which allow it to be easily removed trom the opening for the inspection of 
the surface where contact is made between the yoke and the test sample. 

The spring balance, F, is suspended from an angle iron fastened to the up- 
right rack, /, which engages with the pinion, J. The balance is suspended 
exactly over the centre of the yoke through which the sample passes, to 
avoid any side pull. A spring buffer, K, is provided, which allows perfectly 
free movement of the link holding the sample for a distance of about a", 
and then takes up the jar consequent upon the sudden release of the sample. 
The frame, B, which supports the pulling mechanism, is made of brass, and 
has feet cast at the bottom, by means of which the complete apparatus is 
fastened to the table. Two spring balances are provided, one reading to 30 
lbs. and the other to 100 lbs. These spring balances are of special construc- 
tion, having comparatively long scales. (They were originally made self- 
registering ; but this was found unnecessary, as a reading could be taken 
with greater rapidity and with sufficient accuracy without the self-register- 
ing mechanism.) Any good spring balance may be used. The spring should 
be carefully calibrated from time to time over its whole range ; and if there 
is a correction it will be found convenient to use a calibration curve in cor- 
recting the readings. With a sample §" in diameter, or ^ of a square inch 
area cross-section, the maximum pull required for cast iron is about 25 lbs., 
and for mild cast steel about 70 lbs. 

With the number of turns on the coil given above, the current required 
for obtaining a magnetizing force of J£= 300, is about 12.5 amperes. This 
is as high a value as is ever necessary in ordinary work. For furnishing the 
current a storage battery is ordinarily used, and the variations made by 
means of a lamp board which has in addition a sliding resistance, so that 
variations of about .01 ampere may be obtained over the full range of cur- 
rent from 0.1 ampere to 12.5 amperes. 

The operation of the permeameter is as follows : — 

The sample to be tested is first demagnetized by introducing it into the 
field of an electro-magnet with a wire core, through which an alternating 
current is passing, and gradually removing it from the field of this electro- 
magnet. The sample is then introduced into the opening in the yoke, care 
being taken to see that it can move without friction. Measurements are 
taken with the smallest current to be used first, gradually increasing 
to the highest value desired. In no case should a reading be taken with a 
current of less value than has been reached with the sample in position, 
unless the sample is thoroughly demagnetized again before reading is taken. 
It is usually most convenient to make each successive adjustment of cur- 
rent with the sample out of position, then introduce the sample and give it 
a half turn, to insure perfect contact between the sample and the yoke. The 
lower end of the sample and the surface on which it rests should be care- 
fully inspected to see that no foreign matter of any kind is present which 
might introduce serious errors in the measurements. The pull is made by 
turning the pinion slowly by means of a handle, E, carefully noting each 
position of the index of the spring balance as it advances over the scale, 
and noting the point of release. The mean of three or four readings is 
usually taken as the corrected value for pull, the current in the coil remain- 
ing constant. With practice the spring balance can be read to within less 
than 1% ; and as the square root of the pull is taken, the final error becomes 
quite small, especially with high readings. 

The evaluation of the results for the above permeameter is obtained by 
the use of the following formula : — 

The magnetizing force JC= T , . 



MAGNETIC PROPERTIES OF IRON. 



Where % = number of turns in the magnetizing coil = 223, 
i = current in amperes, 

I = length of magnetic circuit in centimetres, estimated in this 
case as 11.74. 
Substituting the known values in the above formula we have 
OC = 23.8 i. 







Permeameter 




Coil and Sheff 
Fig. 5. 
The number of lines of force per square centimetre, 
(B= 1,317 JI + 3Q.- 



r* 



Where P = pull in lbs. 

A = area of the sample in square inches = 0.3068. 
JC = value of the magnetizing force for the given pull. 



THE PERMBAMETER. 



71 



Substituting the value of A in the above formula we have 
($>= 2,380 VP + 3C- 

There are several sources of error in measurements made by the permea- 
meter which should be carefully considered, and eliminated as far as possible. 

a. The unavoidable air gap between the sample and the yoke where it 
passes through the hole in the upper part of the yoke, together with the 
more or less imperfect contact at the lower end of the sample, increases the 
magnetic reluctance and introduces errors for which it is impossible to make 
due allowance. By careful manipulation, however, these can be reduced 
to a minimum, and be made practically constant. 




b. As the magnetization becomes greater the leakage at the lower end of 
the sample increases more rapidly ; and there is considerable error at very 
high values from this source, as the leakage lines are not broken with the 
rest. 

c. Errors in the calibration and reading of the spring balance. None 
but the best quality of spring balance should be used, and the average of 
several readings taken with the current remaining perfectly constant for 
each point on the (B"3C curve. As the square root of the pull is taken, the 
errors due to reading the spring balance make a larger and larger percent- 
age error in (g as P approaches zero, thus preventing accurate determina- 
tions being made at the beginning of the curve. 



72 



MAGNETIC PROPERTIES OF IRON. 



From the above it will be seen that the permeameter is not well adapted 
for giving the absolute values of the quality of iron and steel, but is especially 
suitable for comparative values, such as are noted in ordinary work, where 
a large number of samples are to be quickly measured. A complete curve 
can be taken and plotted in ten minutes. By suitable comparison of known 
samples measured by more accurate methods, the permeameter readings may 
be evaluated to a sufficient degree for use in the calculations of dynamo 
electric machinery. 



CORE BOSSES. 

These result from Hysteresis and Eddy currents. 

Professor Ewing has given the name Hysteresis to that quality in iron 
which causes the lagging of the induction behind the magnetic force. It 
causes a loss when the direction of the induction is reversed, and results in 
a heating of the iron. It increases in direct proportion to the number of 
reversals, and as the 1.6th power of the maximum value of the induction in 
the iron core. The heat produced has to be dissipated either by radiation 
or conduction, or by both. Steinmetz gives the following formula for hys- 
teresis loss in ergs per cubic centimeter, of iron per cycle ; h = rj (J$ 1-6 , 
where ij =: a constant depending upon the kind of iron. 



Hjsteretic Constants for Different Material*. 



Material. 


Htsteketic Constant. 




.002 


Very thin soft sheet iron 

Thin good sheet iron 


.0015 

.003 
.0033 


Most ordinary sheet iron 

Transformer cores 

Soft annealed cast steel • . . 


.004 
.003 
.008 
.0094 




.012 




.016 




.025 







Eddy Currents are the local currents in the iron core caused by the E.M.F's 
generated by moving the cores in the held, and increase as the square of the 
number of revolutions per second. The cure is to divide or laminate the 
core so that currents cannot flow. These currents cause heating, and unless 
the core be laminated to a great degree, are apt to heat the armature core so 
much as to char the insulation of its windings. 

Wiener gives tables showing the losses by Hysteresis and Eddy currents 
at one cycle per second, under different conditions. These are changed 
into any number of cycles by direct proportion. Following are the 
tables : — 



CORE LOSS. 



73 



Hysteresis factors for Different Core Densities. 

(Wiener.) 



*3% 


Watts dissipated at 


1-1 H 


Watts dissipated at 


A FREQUENCY OF ONE 


fc 


A FREQUENCY OF ONE 


COMPLETE MAGNETIC 


g3g 


COMPLETE MAGNETIC 


a .<* 


CYCLE PER SECOND. 


CYCLE PER SECOND. 


£ H 02 






hi 

2£s 

Ei " O 

fc < o 
cs £ <*< 

< « & 






Sheet iron. 


Iron wire. 


Sheet iron. 


Iron 


wire. 


2 1> ^ 

« < ? 


p.c.ft. 


p. lb. 


p.c.ft. 


per lb. 


p.c.ft. 


per lb. 


p.c.ft. 


perlb. 




V 


tj-^480 


■n 


r)-J-480 


V 


i|-=- 480 


n 


77-H80 


10,000 


1.25 


.0026 


14.3 


.030 


66,000 


25.72 


.0537 


294.0 


.613 


15,000 


2.40 


.0050 


27.4 


.057 


67,000 


26.34 


.0550 


301.0 


.628 


20,000 


3.79 


.0079 


43.3 


.090 


6S,000 


26.97 


.0563 


308.2 


.643 


25,000 


5.42 


.0113 


62.0 


.129 


69,000 


27.61 


.0576 


315.5 


.658 


30,000 


7.30 


.0152 


83.5 


.174 


70,000 


28.26 


.0589 


322.8 


.673 


31,000 


7.70 


.0160 


88.0 


.183 


71,000 


28.91 


.0603 


330.1 


.688 


32,000 


8.10 


J0168 


92.6 


.192 


72,000 


29.56 


.0617 


337.6 


.704 


33,000 


8.50 


.0177 


97.2 


.202 


73,000 


30.22 


.0631 


345.1 


.720 


34,000 


8.91 


.0186 


101.8 


.212 


74,000 


30.89 


.0645 


352.9 


.736 


35,000 


9.33 


.0195 


106.5 


.222 


75,000 


31.56 


.0659 


360.7 


.752 


36,000 


9.76 


.0204 


111.5 


!232 


76,000 


32.23 


.0673 


368.5 


.768 


37,000 


10.20 


.0213 


116.5 


.242 


77,000 


32.91 


.0687 


376.3 


.784 


38,000 


10.65 


.0222 


121.6 


.253 


78,000 


33.60 


.0701 


384.2 


.800 


39,000 


11.10 


.0231 


126.8 


.264 


79,000 


34.29 


.0715 


392.1 


.817 


40,000 


11.55 


.0240 


132.0 


.275 


80,000 


34.99 


.0730 


400.0 


.834 


41,000 


12.01 


.0250 


137.2 


.286 


81,000 


35.69 


.0745 


408.0 


.851 


42,000 


12.48 


.0260 


142.5 


.297 


82,000 


36.40 


.0760 


416.0 


.868 


43,000 


12.96 


.0270 


148.0 


.308 


83,000 


37.11 


.0775 


424.0 


.885 


44,000 


13.45 


.0280 


153.7 


.320 


84,000 


37.82 


.0790 


432.4 


.902 


45,000 


13.95 


.0290 


159.4 


.332 


85,000 


38.54 


.0805 


440.8 


.919 


46,000 


14.45 


.0300 


165.1 


.344 


86,000 


39.27 


.0820 


449.2 


.936 


47,000 


14.95 


.0311 


170.8 


.356 


87,000 


40.01 


.0835 


457.0 


.954 


48,000 


15.45 


.0322 


176.6 


.368 


88,000 


40.75 


.0850 


466.0 


.972 


49,000 


15.96 


.0333 


182.4 


.380 


89,000 


41.50 


.0865 


474.5 


.990 


50,000 


16.48 


.0344 


188.3 


.392 


90,000 


42.25 


.0881 


483.0 


1.008 


51,000 


17.01 


.0355 


194.3 


.405 


91,000 


43.00 


.0897 


491.5 


1.023 


52,000 


17.55 


.0366 


200.6 


.418 


92,000 


43.76 


.0913 


500.0 


1.042 


53,000 


18.10 


.0377 


206.9 


.431 


93,000 


44.53 


.0929 


509.0 


1.064 


54,000 


18.65 


.0388 


213.2 


.444 


94,000 


45.30 


.0945 


518.0 


1.080 


55,0u0 


19.21 


.0400 


219.5 


^157 


95,000 


46.07 


.0961 


527.0 


1.098 


56,000 


19.78 


.0412 


226.0 


.470 


96,000 


46.85 


.0977 


536.0 


1.116 


57,000 


20.35 


.0424 


232.6 


.484 


97,000 


47.63 


.0993 


545.0 


1.135 


58,000 


20.92 


.0436 


239.2 


.498 


98,000 


48.41 


.1009 


554.0 


1.154 


59,000 


21.50 


.0448 


245.8" 


.512 


99,000 


49.20 


.1025 


563.0 


1.173 


60,000 


22.09 


.0460 


252.5 


.526 


100,000 


50.00 


.1041 


572.0 


1.192 


61,000 


22.69 


.0472 


259.4 


.530 


105,000 


54.06 


.1127 


618.0 


1.290 


62,000 


23.29 


.0485 


266.3 


.554 


110,000 


58.23 


.1215 


666.0 


1.388 


63,000 


23.89 


.0498 


273.0 


.568 


115,000 


62.53 


.1305 


715.0 


1.490 


64,000 


24.50 


.0511 


280.0 


.583 


120,000 


66.95 


.1400 


765.0 


1.595 


65,000 


25.11 


.0524 


287.0 


.598 


125,000 


71.50 


.1500 


817.5 


1.705 



74 MAGNETIC PROPERTIES OF IRON. 



The Sten-by-Step Method of Hysteresis Test. 

The samples for hysteresis tests, being generally of sheet iron, are made 
in the form of annular disks whose inner diameters are not less than § of 
their external diameter. A number of these disks are stacked on top of 
each other, and the composite ring is wound with one layer of wire form- 
ing the magnetizing coil of ?i t turns. This coil is connected through a re- 
versing switch to an ammeter in series with an adjustable resistance, and a 
storage battery. A secondary test coil of n 2 turns is connected with a bal- 
listic galvanometer, as shown in Fig. 7. 

BALLISTIC 

GALVANOMETER 




Fig. 7. 

To make the test, adjust the resistance for the maximum exciting current. 
Reverse the switch several times, the galvanometer being disconnected. 
Then connect the galvanometer, and reduce the current by moving the con- 
tact arm of the rheostat up one step. This rheostat must be so constructed 
that an alteration in resistance can be made without opening the circuit even 
for an instant. Note the throw in the galvanometer corresponding to the 
change in exciting current. Follow this method by changing resistance 
step-by-step until the current reaches zero. Reverse the direction, and in- 
crease step-by-step up to a maximum and then back again to zero. Reverse 
once more, and increase step-by-step to the original maximum. In every 
case note and record the value of the exciting current i, and the corre- 
sponding throw of the galvanometer, 0. Form a table having the following 
headings to its columns : — 

i, 3C> e > change of (E, (B- 

Values of /Tare obtained from the formula, 

3C = T n ! , when I = average circumference of the test ring. 
Change of (Bis obtained by the formula, 
10 8 R K 9 



an 2 

where all letters have the same significance as in the formula on page 67. 
Remember that we started in our test with a maximum unknown value of (g, 
and that we gradually decreased this by steps measurable by the throw of 
the galvanometer, and that we afterwards raised the (Bin an opposite direc- 
tion to the same maximum unknown value, and still further reduced this to 
zero, and after commutation produced the original maximum value. Ac- 
cording to this, if due consideration be paid to the sign of the (5J which is 
determined by the direction of the galvanometer throw, the algebraic 
sum of the changes in (B should be equal to zero ; the algebraic sum of the 
first or second half of the changes in (B should be equal to twice the value 
of the original maximum, (g. Taking this maximum value as the first under 
the column of the table headed (B, and applying algebraically to this the 
changes in (B for successive values, we obtain the completed table. Plot 
a curve of J£and($$. The area enclosed represents the energy lost in carry- 
ing the sample through one cycle of magnetization between the maximum 
limits +(B an( i — (B- Measure this area, and express it in the same units as 
is employed for the co-ordinate axes of the curve. This area divided by "Jw 



CORE LOSS. 



75 



gives the number of ergs of work performed per cycle upon one cubic centi- 
meter of tbe iron, the induction being carried to the limits -|- (£>and — (g. 

Tlit" WattiiM'tcr method of Hysteresis Tests. 

Inasmuch as the iron, a sample of which is submitted for test, is generally 
to be employed in the manufacture of alternating-current apparatus, it is 
desirable to make tbe test as nearly as possible under working conditions. 
If the samples be disks, as in the previous method, and these be shellacked 
on both sides before being united into the composite test-ring in order to 
avoid as much as possible foucault current losses, the test can be quickly 
made according to the method outlined in the following diagram : — 




Fig. 8. Wattmeter Test for Hysteretic Constant. 



Alternating current of / alternations per second is sent through the test- 
ring. Its voltage, E, and current strength, i, are measured by the alternating- 
current voltmeter, V, and ammeter, A. If r be the resistance of the test- 
ring coil of % turns, then the watts lost in hysteresis W, is equal to the 
wattmeter reading W — i 2 r. If the volume of the iron be V cubic centi- 
meters, and the cross section of the iron ring be a square centimeters, then 
Steinmetz's hysteretic constant 

_ 10 7 W / V2tt wt/q y-" 

Foucault current losses are neglected in this 
formula, and the assumption is made that the 
current is sinusoidal. 

Eivsiig-'.w Hysteresis Tester. — In this in- 
strument, Fig. 9, the test sample is made up of 
about seven pieces of sheet iron %" wide and 3" 
long. These are rotated between the poles of a 
permanent magnet mounted on knife edges. 

The magnet carries a pointer which moves 
over a scale. Two standards of known hyster- 
esis properties are used for reference. The de- 
flections corresponding to these samples are 
plotted as a function of their bysteresis losses, 
and a line joining the two points thus found is 
referred to in subsequent tests, this line show- 
ing the relation existing between deflection and 
hysteresis loss. The deflections are practically 
tbe same, with a great variation in the thick- 
ness of the pile of test-pieces, so that no cor- 
rection has to be made for such variation. This 
instrument has the advantage of using easily 
prepared test samples. 




Fig. 9. 



Hysteresis Mieter, Used l>y General Electric Co. 

Designed and Described by Fkank Holden. 

During the last few weeks of the year 1892 there was built at the works of 
the General Electric Company, in Lynn, Mass., under the writer's direction, 
an instrument, shown in Fig. 10, by which the losses in sheet iron were 
determined by measuring the torque produced on the iron, which was 
punched in rings, when placed between the poles of a rotating electro-mag- 
net. The rings were held by a fibre frame so as to be concentric with a 



MAGNETIC PROPERTIES OF IRON. 



vertical shaft which worked freely on a pivot bearing at its lower end. 
They had a width of 1 centimeter, an outside diameter of 8.9 centimeters, 
and enough were used to make a cylinder about 
1.8 centimeters high. The top part of this in- 
strument, which rested on a thin brass cylin- 
der surrounding the rings, was movable. On 
the upper surface was marked a degree scale, 
over which passed a pointer, with which the 
upper end of a helical spring rotated. It was 
so constructed that when the vertical shaft 
with the rings and the upper part of the instru- 
ment with the spring was put in place, the 
lower end of the spring engaged witb the shaft, 
and consequently rotated with the rings. A 
pointer moving with the lower end of the spring 
reached to the zero of the degree scale when 
the apparatus was ready for use. By this ar- 
rangement it was found what distortion it was 
necessary to give the spring in order to bal- 
ance the effect of the rotating magnet, and the 
spring having been calibrated, the ergs spent 
on the rings per cycle were determined by mul- 
tiplying the degrees distortion by a constant. 
A coil, so arranged that it surrounded but did not touch the rings, made 
contact at its ends with two fixed brushes that rested in diametrically oppo- 
site positions on a two-part commutator, which revolved with a magnet. 
The segments were connected each to a collector ring against which rubbed 
a brush, the latter two brushes being joined through a sensitive Weston 
voltmeter. If this were so arranged that the coil was at right angles to the 




Fig. 10. Hysteresis Meter. 





1000 2000 3000 4000 


5000 C000 7000 


T 




(|3- " M^ 




DUGf-IOIjl hPER-CYCLE 






r-r-y^ — few 5 






t±""2-==i ¥ * 












: / 






- * 








cuoo -- 




tzo^^i^r ' 




:±::==J-==-z^ 






^ 






_y 






: T :: 


-- = 5P= = = I-J 










A- '- 












7 
























= = = - a \\~ 




















I »-- J 








-1000 -- 







5000 

4000 



100 200 300 400 500 GOO 
REVOLUTIONS PER MINUTE, 



Fig. 11. 



induction, when the brushes changed contact from one segment to the other, 
it is evident, the self-induction of the circuit being negligible, that the 
mean value of the current in the circuit was proportional to the total flux 
through the coil. Knowing the constant of the voltmeter, the deflection was 
easily calculated from the speed of the magnet, the number of turns in the 
coil, cross-section of the rings, and the resistance of the circuit. From an 
induction of 2,000 gausses to at least 10,000 gausses, the leakage across the 
interior space of the rings was negligible. 

Carried on the shaft below the magnet was a pulley around which passed 
a flat belt driven with a pulley of the same size on an electric motor, so that 
the speed of the magnet could be found by observing that of the motor. In 
operating, the deflections to be produced on the voltmeter at a certain speed, 
with the desired induction in the rings, were first calculated. Five hundred 



HYSTERESIS METER. 



77 



revolutions per minute was generally adopted as the speed in this case. 
The motor being run at the desired speed, the magnetizing current was ad- 
justed until the calculated deflection was produced on the voltmeter. Keep- 
ing the magnetizing current constant, the speed was changed successively in 
value to certain values, and the corresponding distortions of the* spring 
necessary to balance the effect of the magnet noted. When this process 
was carried out at different induction values, and the ergs expended per 
cycle on the rings plotted as a function of the speed, a series of lines was 
produced, as shown in Figs. 11 and 12. It was found that the slope of the 
lines decreased very rapidly with the decrease in thickness of the iron sheet 
used so as to indicate that had it been thin enough the slope would have 
been zero between 100 and 800 revolutions per minute, which was about the 
highest speed permissible. From this it would seem that, in these tests, the 
total loss per cycle had two components ; one remaining constant, due to 
hysteresis, and the other varying as the speed of the magnets, due to cur- 
rents induced in the iron. 

Fig. 15 gives observations of eddy current loss and thickness of iron sheet 
on this assumption. The line drawn is a parabola, so that it would appear 
that with the range of observations made the loss varied about as the square 
of the thickness of the sheets. 



.4000 5000 6000 7000 



8000 
'7000 
6000 
£000 
4000 





















































r 


r 












' 














































1 DUC 


10 






































^F 




































X 






































± 
























f 














-"PER 




























































































/ 




































/ 




































/ 














































































































r 




































/ 




































/ 












































































































/ 



















































































































































































































































































































































































































7000 
6000 



5000 
4000 

3000 



100 200 300 .400 500 600 700 

REVOLUTIONS PER MINUTE 

Fig. 12. 

Fig. 11 gives lines from iron .04 centimeters thick. Speed readings were 
not taken lower than 250 revolutions per minute, as it had been found that 
the lines were always straight, and speeds below this value could not be 
read with the tachometer available for this particular test. Plotting the 
hysteresis as a function of the induction, in this case the points are all quite 
close to a curve whose equation is, Ergs = A constant x (Density per square 
centimeter) 1 - 47 , three points in the latter calculated curve being shown by 
the crosses. The iron, a test on which is shown in Fig. 12, was .1 centimeter 
thick, and shows a greater eddy current loss. The equation for the hystere- 
sis curve for this sample is, Ergs = A constant x (Density per square centi- 
meters) 1-4 , some points in the latter curve being shown by crosses, as before. 

The eddy current losses for these two samples are plotted as functions of 
the induction in Fig. 14. The curves drawn are parabolas; showing that in 
these cases the eddy current loss varied approximately as the square of the 
induction, although there were often greater variations from that law than 
these two samples show. The average exponent for the hysteresis curves 
was a little over 1.5, although it varied from 1.4 to 1.7. Rings tested in this 
manner were wound and tested with a ballistic galvanometer, using the 
step-by-step method. There were discrepancies of as much as 4 per cent be- 
tween the two results, but an average of ten tests showed the ballistic gal- 
vanometer method gave results 2.5 per cent lower than the other. This 
difference is easily attributable to experimental errors. 

It being noticed that for a given induction in the rings, the magnetizing 
currents for different samples did not vary much, it was planned shortly 



78 



MAGNETIC PROPERTIES OF IRON. 




after completing the above apparatus to construct a modified instrument 
which would use electro-magnets of such high reluctance that the variations 
of the rings would be negligible, and induction 
be dependent only on the current. By making 
the electro-magnets of suitable iron and of 
about one-third the cross-section of the rings 
used, the iron may he so highly saturated 
that the induction will remain quite constant 
under considerable variation in the magnet- 
izing current, thus rendering unnecessary 
any accurate comparisons of magnetizing 
currents, and the rings can be at about their maximum permeability when 
thus magnetized. Such an instrument is shown in Fig. 13 in its original ex- 
perimental form, with the rings in position ready for test. The rings are 
here allowed to rotate in opposition to the action of a spring and carry a 
pointer over a scale, so that is is quite direct reading. Twenty-live compar- 



Fig. 



13. Modified Hyster- 
esis Meter. 



90C0 - -T" TT 




onm '.'" 


i-" - 


8000 |N i uc |,^ N " S" 

































































200 400 600 800 1000 1200 1400 1600 

ergs per cm 3 per cycle 

eddy current loss 
speed 700 rev's per win. 
Fig. 14. 

isons of this instrument with the original one gave results that agreed 
within 6 per cent in all cases, and more than half were within 2 per cent of 
agreement. Permanent magnets had been previously tried, but the attempt 
seemed to show that the instrument would not, in that case, compare sam- 
ples of iron widely different in character ; and the writer not being able to 























































































































































































































































































































p 


























































































































































T 


H 


CKNE 


3S 


IN 


AM 
















y 




























































y 






























































y 






























































y 






























































' 






























































y 






























































, 


' 




























































- 


/ 


' 






























































/ 




























































































































., 




/ 











































































































































































































































































































































































































































































100 £00 300 400 500 000 700 800 900 10001100 12OO130014OO15OO10O0 1700 

erg8 per cm' 3 per cycle 
Fig. 15. 

give any attention to the matter, no further investigations in that direction 
were attempted. 

The instrument first described has been in use continuously since its com- 
pletion at the works of the General Electric Company, in Schenectady. 



EDDY CURRENT FACTORS. 



79 



edd1 currjbwt factors for different 

cork densities aid tor various 

eamfnations. 

(Wiener.) 



u o * 


Watts dissipated 


B|B 


Watts dissipated 


PER CUBIC FOOT OF 


*%*< 


PER CUBIC FOOT OF 


B°S 


IRON AT 


A FRE- 


H ° fa 1 


IRON AT A FRE- 


» as 


QUENCY OF 1 CYCLE 


ggfa 


QUENCY OF 1 CYCLE 


£ o 


PER SECOND. 


PER SECOND. 


^ r-l fa 
B'9 












id 8* 


Thickness of lamination,^ 


|3sa 

^ ^ & 


Thickness of lamination, 5 




















.010" 


.020" 


.040" 


.080" 




.010" 


.020" 


.040" 


.080" 


10,000 


.0007 


.003 


.012 


.046 


66,000 


.0315 


.126 


.503 


2.013 


15,000 


.0016 


.007 


.026 


.104 


67,000 


.0325 


.130 


.519 


2.075 


20,000 


.0029 


.012 


.046 


.185 


68,000 


.0335 


.134 


.534 


2.137 


25,000 


.0045 


.018 


.072 


.288 


69,000 


.0345 


.138 


.550 


2.200 


30,000 


.0065 


.026 


.104 


.416 


70,000 


.0355 


.142 


.566 


2.265 


31,000 


.0070 


.028 


.111 


.444 


71,000 


.0365 


.146 


.582 


2.330 


32,000 


.0074 


.030 


.118 


.472 


72,000 


.0375 


.150 


.599 


2.396 


33,000 


.0079 


.032 


.126 


.503 


73,000 


.9385 


.154 


.616 


2.463 


34,000 


.0084 


.034 


.134 


.534 


74,000 


.0396 


.158 


.633 


2.530 


35,000 


.0089 


.036 


.142 


.567 


75,000 


.0407 


.163 


.650 


2.600 


36,000 


.0094 


.038 


.150 


.600 


76,000 


.0418 


.167 


.668 


2.670 


37,000 


.0099 


.040 


.158 


.633 


77,000 


.0429 


.171 


.685 


2.740 


38,000 


.0104 


.042 


.167 


.667 


78,000 


.0440 


.176 


.703 


2.810 


39,000 


.0110 


.044 


.176 


.703 


79,000 


.0451 


.180 


.721 


2.883 


40,000 


.0116 


.046 


.185 


.740 


80,000 


.0462 


.185 


.740 


2.958 


41,000 


.0122 


.049 


.194 


.777 


81,000 


.0474 


.190 


.758 


3.033 


42,000 


.0128 


.051 


.204 


.815 


82,000 


.0486 


.194 


.777 


3.108 


43,000 


.0134 


.054 


.214 


.855 


83,000 


.0498 


.199 


.796 


3.184 


44,000 


.0140 


.056 


.224 


.896 


84,000 


.0510 


.204 


.815 


3.260 


45,000 


.0146 


.059 


.234 


.937 


85,000 


.0523 


.209 


.835 


3.340 


46,000 


.0153 


.061 


.245 


.979 


86,000 


.0535 


.214 


.855 


3.420 


47,000 


.0160 


.064 


.256 


1.022 


87,000 


.0548 


.219 


.875 


3.500 


48,000 


.0167 


.067 


.267 


1.066 


88,000 


.0560 


.224 


.895 


3.580 


49,000 


.0174 


.070 


.278 


1.110 


89,000 


.0573 


.229 


.916 


3.662 


50,000 


.0181 


.072 


.289 


1.055 


90,000 


.0586 


.234 


.937 


3.745 


51,000 


.0188 


.075 


.300 


1.200 


91,000 


.0599 


.240 


.958 


3.830 


52,000 


.0195 


.078 


.312 


1.248 


92,000 


.0612 


.245 


.979 


3.915 


53,000 


.0202 


.081 


.324 


1.297 


93,000 


.0625 


.250 


1.000 


4.000 


54,000 


.0210 


.084 


.337 


1.346 


94,000 


.0638 


.255 


1.021 


4.085 


55,000 


.0218 


.087 


.349 


1.397 


95,000 


.0651 


.261 


1.043 


4.170 


56,000 


.0226 


.091 


.362 


1.448 


96,000 


.0665 


.266 


1.064 


4.257 


57,000 


.0234 


.094 


.375 


1.500 


97,000 


.0679 


272 


1.086 


4.345 


58,000 


.0242 


.097 


.389 


1.555 


98,000 


.0693 


.277 


1.109 


4.436 


59,000 


.0251 


.101 


.403 


1.610 


99,000 


.0707 


.283 


1.132 


4.528 


60,000 


.0260 


.104 


.416 


1.665 


100,000 


.0722 


.289 


1.156 


4.622 


61,000 


.0269 


.108 


.430 


1.720 


105,000 


.0797 


.319 


1.274 


5.095 


62,000 


.0278 


.111 


.444 


1.776 


110,000 


.0875 


.350 


1.398 


5.593 


63,000 


.0287 


.115 


.458 


1.833 


115,000 


.0955 


.382 


1.528 


6.113 


64,000 


.0296 


.118 


.473 


1.891 


120,000 


.1040 


.416 


1.664 


6.655 


65,000 


.0305 


.122 


.486 


1.951 


125,000 


.1128 


.451 


1.806 


7.222 



80 



MAGNETIC PROPERTIES OF IRON. 



ipiciric EitfKitGir DisiiPAiioir m abmaiihe 

COItE. 

(Weiner.) 







Hysteresis 


LOSS 


FOR 


Eddy-current loss for 






SHEET IRON AT FRE- 


.030 // (.075 CM.) LAMINATION, 


Magnetic 


QUENCY OF ONE MAG- 


AT ONE CYCLE PER SECOND 


density. 


NETIC CYCLE PER 


PROPORTIONAL TO FRE- 






SECOND (IN 


WATTS). 


QUENCY (IN WATTS). 




Lines 


















Gaus- 


of force 


Per 


Per 


Per 


Per 


Per 


Per 


Per 


Per 


ses. 


per 
sq. in. 


cm. 3 


c. ft. 


kg. 


lb. 


cm. 3 


eft. 


kg. 


lb. 


2,000 


12,900 


.00007 


1.98 


.0091 


.0041 


.0000004 


.011 


.000051 


.000023 


3,000 


19.350 


.00013 


3.68 


.0140 


.0077 


.0000009 


.026 ! .000119 


.000054 


4,000 


25,800 


.00020 


5.75 


.0265 


.0120 


.OOOUOIO 


.046 ! .000212 


.000096 


5,000 


32,250 


.00029 


8.20 


.0378 


.0171 


.0000025 


.071 .000327 


.000148 


6,000 


38,700 


.00039 


11.03 


.0508 


.0230 


.0000036 


.102 ! .000471 


.000213 


7,000 


45,150 


.00050 


14.15 


.0652 


.0295 


.0000049 


.139 


.000640 


.000290 


8,000 


51,600 


.00062 


17.5 


.0806 


.0365 


.0000064 


.181 


.000833 


.000377 


9,000 


58,050 


.00074 


20.9 


.0963 


.0436 


.0000081 


.229 


.001054 


.000478 


10,000 


64,500 


.00087 


24.6 


.1133 


.0513 


.0000100 


.283 


.001303 


.000590 


11 ,000 


70,950 


.00102 


28.3 


.1303 


.0590 


.0000121 


.343 


.001580 


.000715 


12,000 


77,400 


.00118 


33.1 


.1524 


.0690 


.0000144 


.408 


.001878 


.000S50 


13.000 


83.850 


.00134 


37.9 


.1745 


.0790 


.0000169 


.479 


.002204 


.000998 


14,000 


90,300 


.00150 


42.7 


.1966 


.0890 


.0000196 


.555 


.002553 


.001157 


15.000 


96,750 


.00168 


47.5 


.2193 


.0990 


.0000225 


.637 


.002923 


.001328 


16,000 


103,200 


.00187 


52.9 


.2440 


.1103 


.0000256 


.725 


.003340 


.001512 


17,000 


109,650 


.00206 


58.3 


.2680 


.1212 


.0000289 


.818 


.003770 


.001708 


18,000 


116,100 


.00225 


63.7 


.2932 


.1328 


.0000324 


.917 


.004220 


.001911 


19,000 


122,550 


.00246 


69.6 


.3200 


.1450 


.0000361 


1.022 


.004710 


.002130 


20,000 


129,000 


.00267 


75.6 


.3480 


.1575 


.0000400 


1.133 


.005225 


.002362 



ELECTRO-MAGNETS. 



MOPERTIFS OF, 



Residual Magnetism is the magnetization remaining in a piece of magnetic 
material after the magnetizing force is discontinued. 

Betentiveness is the measure of the magnitude of residual magnetism. 

Coercive Force is the force which holds the residual magnetism, and is 
measured by the strength of the reverse field required to remove all mag- 
netism. 

Permanent magnetism is residual magnetism of great coercive force, as in 
hard steel, which has little retentiveness ; while soft iron has great reten- 
tiveness but little coercive force. 

The following paragraphs are condensed from S. P. Thompson's " The 
Electromagnet." 

Magrneto-lttotive Force. — The magneto-motive force, or magnetiz- 
ing power of an electro-magnet is proportional to the number of turns of 
wire and the amperes of current flowing through them ; that is, one ampere 
flowing through ten coils or turns will produce the same magneto-motive force 
as ten amperes flowing through one coil or turn. 

If n = number of turns in the coil, 
1= amperes of current flowing, 

1.257 = ~ (to reduce to C. G. S. units). 

Magneto-motive force = 1.257 x nl= $. 

Intensity of Magnetic Force. — Intensity of magnetic force in an 
electro-magnet varies in different parts of the magnet, being strongest in 
the middle of the coil, and weaker toward the ends. In a long electro-mag- 
net, say a length 100 times the diameter, the intensity of magnetic force will 
be found nearly uniform along the axis, falling off rapidly close to the ends. 

In a long magnet, such as described above, and in an annular ring wound 
evenly over its full length, the value of the magnetic force, J£, is deter- 
mined by the following expression : — 

3£= 1.257 — y , in which 1= centimeters. 

If the length is given in inches, then 

3C — .495 -j — , in which I/,— inches. 

If intensity of the magnetic force is to be expressed in lines per sq. inch, 

3C//= 3.193 X^. 

Value of 3C at tlte centre of a Single-turn of Conductor. — 

In a single ring or turn of wire of radius r, carrying / amperes of current 



9 r 

0C= w X -= -6284 X 



10 ~ r ' r 

Force on Conductor (carrying- current) 
in a Magnetic Field. — A conductor carrying 
current in a magnetic field is repelled from the 
field Dy a certain mechanical force acting at right 
angles both to the conductor itself and to the lines 
of force in the field ; see cut. 

The magnitude of tbis repelling force is deter- 
mined as follows, assuming the field to be uniform. 

3£ =: magnetizing force, or intensity of the field. 
I =z length of conductor across the field in cm. 
l /t =z ditto in inches. 

/= amperes of current flowing in the conductor, 
F— repelling force. 

F in dynes =: ^- — F in dynes — ''. ■ F in grains = 

81 




FIG. 1. Action of Mag- 
netic Field, on Con- 
ductor carrying cur- 
rent. „„ , r 

3£„h,l 



82 ELECTRO-MAGNETS. 

Work done by Conductor (carrying Current) in moving 
across a Magnetic field. 

tJV^ c ^ ducto 5 1 descri , b ed in the preceding paragraph he moved across 
the field of force, the work done will be determined as follows • in addition 
to the symbols there used, let b = breadth of field in and across which the 
conductor is moved ; w = work done in ergs. ^iumj wnicn tne 

w=I r b= mu t 

10 ' 
bl = area of field, 
N=bl x 4> = number of lines of force cut, 

NI 
W =W 

Rotation of Conductor (carrying- current) around a Magnet 

JPole. 

If a conductor (carrying current) be so arranged that it can rotate about 
tne pole of a magnet, the force producing tbe rotation, called torque, will be 
determined as follows : The whole number of lines of force radiating from 
the pole will be 4 77 times the pole strength m. 

47r ml 
w — ~^Tq— = 1.257 ml. 

Dividing by the angle 2ir, the torque, T, is 

T — w= 2mL 

fl Every magnetic circuit tends to place itself so as to embrace the maximum 

^sssi^^r as current flowi,,g - the 

Magnetic flux = Ma g"eto-motive fo rce 
reluctance 

+ =*. 
(ft. 

<rr — 47r nI 

. 1.257 nl 
An 

1.257 



EXCITING POWER AND TRACTION. 



83 



If dimensions are in inches, and A is in square inches, then 
nl=<t>-^- X -3132. 
and $ = (ft" A". 
The Law of Traction. — The formula for the pull or lifting-power 
of an electro-magnet is as follows : — 

Pull (in dynes) = ^- . 



Pull (in grammes) : 



Pull(in pounds) = - 



(ft 2 -* 
8tt X 981 

(B 2 ^ 



In inch measure, Pull (in pounds): 



11,183,000 
A" 



72,134,000 ' 
Magnetization and Traction of Electro Magnets. 



® 


®" 


Dynes 


Grammes 


Kilogs 


Pounds 


Lines per 


Lines per 


per 


per 


per 


per 


sq. cm. 


sq. inch. 


sq. cm. 


sq. cm. 


sq. cm. 


sq. inch. 


1,000 


6,450 


39,790 


40.56 


.04056 


.577 


2,000 


12,900 


159,200 


162.3 


.1623 


2.308 


3,000 


19,350 


358,100 


365.1 


.3651 


5.190 


4,000 


25,800 


636,600 


648.9 


.6489 


9.228 


5,000 


32,250 


994,700 


1,014 


1.014 


14.39 


6,000 


38,700 


1,432,000 


1,460 


1.460 


20.75 


7,000 


45,150 


1,950,000 


1,987 


1.987 


28.26 


8,000 


51,600 


2,547,000 


2,596 


2.596 


36.95 


9,000 


58,050 


3,223,000 


3,286 


3.286 


46.72 


10,000 


64,500 


3,979,000 


4,056 


4.056 


57.68 


11,000 


70,950 


4,815,000 


4,907 


4.907 


69.77 


12,000 


77,400 


5,730,000 


5,841 


5.841 


83.07 


13,000 


83,850 


6,725,000 


6,855 


6.855 


97.47 


14,000 


90,300 


7,800,000 


7,550 


7.550 


113.1 


15,000 


96,750 


8,953,000 


9,124 


9.124 


129.7 


16,000 


103,200 


10,170,000 


10,390 


10.390 


147.7 


17,000 


109,650 


11,500,000 


11,720 


11.720 


166.6 


18,000 


116,100 


12,890,000 


13,140 


13.140 


186.8 


19,000 


122,550 


14,360,000 


14,630 


14.630 


208.1 


20,000 


129,000 


15,920,000 


16,230 


16.230 


230.8 



Exciting' Power and Traction. — If we can assume that there is 
no magnetic leakage, the exciting power may be calculated from the follow- 
ing expression ; all dimensions being in inches, and the pull in pounds. 



nl= [ 



\"l" 



X .3132. 



($>" = 



I" X .31 32 ' 
Pull 



w/=2661X — X 
If dimensions are in metric measure, 



also, (ft" = 8494 y 



Pull 
Area" 



(ft = 1316.6 



u 



w/=3951 



Pull in lbs. 



V' 



Area in sq. ins. 



Pull in kilos 
Area in sq. cms 

(£ = 4965^: 



Pull in kilos. 
Area sq. cm. 



84 



ELECTRO-MAGNETS. 



The 
D = 

d = 

t = 
L = 

K — 
V= 

N = 
T = 
n=z 
p = 

B = 



1* 'iutling- of IWag-net Coils. 

following nomenclature is employed : — 
diameter of insulated wire in mils, 
diameter of bare wire in mils. 

thickness of insulation on wire in inches (i.e., — 



— d> 



t0 inchef' 11 ° f Wll ' e hl COil in feet ' a ' & ' k ' and Z = coil dimensions in 

ratio of diameter of insulated wire to bare wire. 

volume of winding space in cubic inches. 

total number of convolutions on spool. 

number of layers of wire on spool. 

number of convolutions per linear inch. 

^S ohVs n at n io r c a ) ti0nal ° hmS ° f mil " f ° 0t ° f PUI * e C ° Pper Wire ' 
total resistance of coil in ohms. 
r = resistance per foot of wire in ohms. 

/=-= feet in one ohm. 

lm = mean length of convolution in inches. 

The winding will vary between two extremes, one the " square " winding 

in which it is assumed that 
the convolutions lie to- 
gether as if the wire was 
of square cross-section, and 
the other the "conical" 
winding in which it is as- 
sumed that the wires lie 
together as if the wire was 
of hexagonal cross-section. 
On the assumption that 
the same volume is occu- 
pied by insulating mate- 
rial about 15 per cent more 
copper volume is obtained 
by the " conical " method 
of winding. 
The square winding is 









f 




«-- 1 * 




| 




1 

b 




a 
1 




1 




i 




i 
h 




1 




i 







Fig. 2. 



assumed in the following, unless otherwise specified. 

The diameter of wire necessary to fill a given coil space with a given num 
ber of convolutions is 



d= \/- 



1000000 I h 

N 

1000000 I h 

K*N 



4 /500000 / (a - 


-&) 


- * If 


_ * /500000 I (a - 


-.6) 



K*N 



The total length of wire of given diameter which can be wound in a given 
coil space is 

65450 I (a 2 — £ 2 ) 



L = 



D* 



From the above formula the dimensions of a spool to hold a specified length 
of wire of given diameter may be determined. 
If a and b are known 

1= LD2 



If b and I are known 
If a and I are known 



65450 (a 2 — W) 

_ k l&L + 65450 lb* 
a ~ V 65450"T~ 



'65450 lb"-—B' , -L 



65450 I 



WINDING OF MAGNET COILS. 



85 



The resistance of a coil expressed as a function of tne volume is 

_ 862500 V 

If the volume of wire is increased ten per cent to allow for the layers fit- 



ting into one another, 



948700 V 
Z> 2 d 2 



Hence the diameter of wire necessary to fill a given volume with a given 
resistance is 



d* = 



9 48700 V 
~K°-R 



The last three formula are general, whatever the shape of the spool, i.e., 
whether the core is of circular, square, rectangular, elliptical, etc., cross- 

Se The I next smaller gauge number than the diameter corresponding to the 
formula should be used in order to allow for irregularities in winding and 
for insulation between the layers. 
If R is taken at other than 68° F (20° C), a new value of R, i.e., R', must be 



taken, where 



R' = R (1 + 0.0022 6/), 



where 0/ is the rise in temperature above 68° F. ,.,,,«. t ,„ 

A formula known as Brough's formula is often applicable to the calcula- 
tions of the diameter of wire necessary to give a stated resistance. 
For circular cores, 



Kv 



677400 (a 2 — ft 2 ) I 
R 



+ £■ 



T 









<=.— 


B *-* 


■■■! 

{ 




t 

\ 

i 




. J < 


1 

I 




i. 


1 


i 







Fig. 3. 



Fig. 4. 




KG.5. 



For square cores, Fig. 3 
d 



_ F , /862500 (a 2 — & 2 ) Z _j_ ^l 2 _ j. 



For rectangular cores, Fig. 4, 



rf _r / 431250lZ= a) {A + ^ + « + *>) + ff ~| *_ . 
For core made up of square and two semi-circles, Fig. 5, 



radius of core-circle, b. 
radius of outer-circle, b. 



86 



Ks/' 



ELECTRO-MAGNETS. 



862500 (B — b) [n (B + b) -f 2 a] 



LI 



-'J 



Thickness of Wire Insulation. — The thickness of insulation upon 
wire varies with the manufacturer, and no fixed value can he given to cover 
all cases. The following table represents the practice of several large man- 
ufacturers. To determine the diameter of insulated wire, add to the dia- 
meter of the bare wire. 





FOR COTTON. 


FOR 


SILK. 


B & S Gauge 


Single 


Double 


Single 


Double 


OtolO 
10 to 18 
18 up 


7 mils 
5 mils 
4 mils 


14 mils 
10 mils 
8 mils 


2 mils 


4 mils 



The above values correspond to It in the formulae. 

Relation of JLmpere -turns to Dimensions of Coil. 

For a coil of stated dimensions it can be shoAvn that 

Ed? 



NI. 



.16 



lm (1. + 0.0022 0/) 
where E = difference of potential across terminals of coil. 

The ampere-turns are independent of the length of the coil, of the thick- 
ness of insulation, and of the method of winding, depending upon the 
diameter of the wire, the mean length of a turn, and the temperature of 
the coil. 

To keep the number of ampere-turns constant in a coil of given volume, 
d°- of the wire must vary inversely as E. 

Relations Holding- between Constants of Coils. 

In the following it is assumed that the thickness of insulation is propor- 
tional to the diameter of wire, and that all coils are uniformly wound. The 
results obtained under this consideration are practically but not strictly 
correct. 

The weight of copper required to fill a given coil volume is constant, 
whatever tbe size of the wire used. 

The resistance in a given volume varies inversely as the fourth power of 
the diameter of the wire used. 

The resistance in a given volume varies inversely as the square of the 
cross-sectional area of the wire used. 

The number of convolutions in a fixed volume varies inversely as the 
square of the diameter, or inversely as the cross-sectional area of the wire 
used. 

The resistance of a coil of given volume varies directly as the square of 
the number of turns. 

The magnetic effect produced by an electro-magnet of given shape, size, 
and construction is proportional to the product of the current into the 
square root of the resistance of the coil. 

If two coils of same dimensions are wound with different size wire, the 
current must vary with the cross-sectional area of the wire, in order to 
obtain the same heating effect, or same temperature rise. 

For same energy loss E 2 must vary inversely as (area) 2 of wire, or for 
same heating effect the voltage across terminals of coil must vary inversely 
as the cross-sectional area of the wire used. 



AMPERAGE AND DEPTH OP WINDING POP. MAGNETS. 87 



AETEHWATINCJ-CUItiaENT EEECTMO-MACJNETS, 

The cores of electro-magnets to be used Avith alternating currents must be 
laminated, and the laminations must run at right angles to the direction in 
which eddy currents would be set up. Eddy currents tend to circulate par- 
allel to the coils of the wire, and the laminations must therefore be longitu- 
dinal to or parallel with the axis of the cores. 

The coils of an alternating-current electro-magnet offer more resistance to 
the passage of the alternating current than the mere resistance of the con- 
ductor in ohms. This extra resistance is called inductance, and this com- 
bined with the resistance of the conductor in ohms produces the quality 
called impedance. (See Index for Impedance, etc.) 

If L = coefficient of self-induction, 
2Tz= periods per second, 
B =- resistance, 



and, 



Impedance = Vi2 2 + 47i- 2 iV 2 i 2 ; 

Maximum E.M.P. 



Maximum current : 
Mean current : 



Impedance 

Mean E.M.E. 

Impedance. 

If the current lags behind the E.M.P. by the angle <f>, then 

Mean E.M.F. 

Mean current — — - — — X cos 6. 

Resistance 

HEATIIG OF MAGKET COIIS. 

Professor Forbes. 
/= current permissible. 

r x = resistance of coil at permissible temperature. 
Permissible temperature = cold r x 1.2. 

t =i rise in temperature C°. 

s = sq. cms. surface of coil exposed to air. 

^ .0003 x t x~s 
~ .24 x r t ' 

I»EItItIISSIBEE AMPEBACJl AND PERMI§§IBIE 

DEPTH OP WINDING EOR MAOHTETi WITH 

COTTON-COVERED WIRE. 

(Walter S. Dix, Electrical Engineer, Dec. 21, 1892.) 



/ 12 X W 



M 

Where /= current ; 

W= emissivity in watts per sq. inch ; 
to = ohms per mil-foot ; 
M — circular mils ; 
T= turns per linear inch ; 
n = number of layers in depth. 
The emissivity is taken at .4 watt per sq. in. for stationary magnets for a 
rise of temperature of 35° C. (63° F.). For armatures, according to Esson's 
experiments, it is approximately correct to say that .9 watt per sq. in. will 
be dissipated for a rise of 35° C. 

The insulation allowed is .007 inch on No. to No. 11 B. and S. ; .005 inch 
on No. 12 to 24 ; and .0045 inch on No. 25 to No. 31 single ; twice these values 
for insulation of double-covered wires. Fifteen per cent is allowed for 
imbedding of the wires. 

The standard of resistance employed is 9.612 ohms per mil-foot at 0°. The 
running temperature of tables is taken at 25° + 35° = 60° C. The column 
giving the depth for one layer is the diameter over insulation. 



88 



ELECTRO-MAGNETS. 



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AMPERAGE AND DEPTH OF WINDING FOR MAGNETS. 89 



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SPACES OCCUPIED BY WIRES. 



91 



Table of Spaces occupied by Wire* of different Sizes, witis 

Single Cotton Insulation, tog-etber with Data of 

the Copper. 

Compiled by Schuyler S. Wheeler. 







Data of the Insulated Wire. 








bib 






















































w S.S 


Pi 

c« . 








. A 


A 


. A 






us£ 


.S«} . 




S>A 


^A 


32 




3 2 




No. 


43 ^tj 


oj^ bC 


02 £ 


£5 


£S 


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o 


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o 


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2 
3 
4 


4.5 


4.87 


22.1 


1.84 


.0004576 


.24 


7. 


4 


.75 


5 


5.09 


5.82 


29.6 


2.46 


.000773S 


.24 


9. 


5 


.74 


6 


5.66 


6.41 


36.3 


3.02 


.0011963 


.24 


11.5 


6 


.74 


7 


6.2 


7.3 


45.3 


3.77 


.001780 


.24 


14. 


7 


.73 


8 


7.05 


8. 


56.5 


4.7 


.0029654 


.24 


17.5 


8 


.73 


9 


7.66 


8.42 


64.5 


5.37 


.0042574 


.24 


22. 


9 


.73 


10 


8.54 


9.6 


82. 


6.83 


.00683 


.238 


27. 


10 


.72 


11 * 


9.7 


11. 


116.7 


9.72 


.012254 


.236 


34. 


11 


.72 


12 


11.2 


12.8 


143.4 


11.95 


.0150654 


.233 


42. 


12 


.71 


13 * 


12. 


14. 


168. 


14. 


.03627 


.23 


55. 


13 


.71 


14 


13. 


15.4 


200. 


16.66 


.0431627 


.227 


68. 


14 


.70 


15 


15.37 


17.9 


275.5 


22.96 


.071520 


.224 


87. 


15 


.68 


16 


16.74 


19.4 


324.7 


27.06 


.108757 


.22 


110. 


16 


.64 


17 


17.74 


21.33 


378.4 


31.53 


.15980 


.217 


140. 


17 


.62 


18 * 


19.5 


23. 


448.5 


37.38 


.2389 


.19 


175. 


18 


.61 


19 


22.77 


24.9 


567. 


47.25 


.39165 


.185 


220. 


19 


.60 


20 


25.7 


29.7 


763.3 


63.60 


.6464 


.184 


280. 


20 


.58 


21 


28.3 


32.5 


920. 


76.6 


.98163 


.182 


360. 


21 


.57 


22 


31. 


36. 


1116. 


93. 


1.502 


.18 


450. 


22 


.55 


23 


34.4 


40.36 


1390.3 


115.86 


2.36 


.178 


560. 


23 


.52 


24 


36.9 


44.6 


1649. 


137.4 


3.53 


.168 


715. 


24 


.45 


25 


38. 


47. 


1790. 


149.2 


4.734 


.145 


910. 


25 


.43 


26 * 


42. 


50.5 


2100. 


170. 


7. 


.14 


1165. 


26 


.41 


27 * 


48. 


55.5 


2600. 


210. 


10.5 


.135 


1445. 


27 


.40 


28 


53.28 


61.1 


3256. 


271.3 


17.63 


.13 


1810. 


28 


.39 


29 * 


59. 


68. 


4000. 


335. 


27. 


.125 


2280. 


29 




30. 


63.26 


76.8 


4860. 


405. 


41.84 


.121 


2805. 


30 


.38 


31 




















32 




















33 




















34 




















35 




















36 





















* Estimated. 



RELATION AND DIMENSIONS OF CON- 
DUCTORS FOR DISTRIBUTION. 



RELATION OF E.M.F.; < I It It I VI DISTANCE, 

CROSS-8ECII02T, AN» WFIOHT Of 

COKDIJCTORi. 



a. Current or E.M.F. varies directly with the amount of energy trans- 
mitted. 

b. Given the work done, loss on the line, and the E.M.F. at the motor 
terminals and point of distribution ; then the cross-section of conductor 
varies directly with the distance and weight as the square of the distance. 

c. With the same conditions as above, the weight of conductor will vary 
inversely as the square of the E.M.F. at the motor terminals. 

d. With a given cross-section of conductor, the distance over which a 
given amount of power can be transmitted will vary as the square of the 
E.M.F. 

e. Given, the weight of conductor, the amount of power transmitted, and 
the loss in distribution ; then the distance over which the power can be 
transmitted will vary directly as the E.M.F. 



PRECI§IO]V OF CALCULATIOU8 OF DIIIRIRVT- 
TXG SYSTEMS. 

While it is possible and in every way the best to make complete compu- 
tations for the conductors for isolated plants and for plants of a permanent 
nature, it is practically impossible to make anything like precise computa- 
tions for large public systems of distributions, such as a large Edison 
system. 

In the early days of the Edison stations, exact sizes of conductors were 
computed for entire systems ; but when the network system was introduced, 
and it became possible to keep the E.M.F. constant all over a system by 
varying the number of feeders, all such exact computations were dropped ; 
and to-day such systems are equipped with a few standard sizes of conduc- 
tors, feeders being of one or two sizes only, and mains being of but two or 
three sizes, judgment of the management being used as to which size will 
best fit given conditions. 



ECONOMICAL CONDITIONS. 

In the laying out of a system of electrical distribution, there are eight 
points to bear in mind in order to obtain the best economy ; and they have 
been so well stated by Abbott, that I quote from his book the following : — 

" 1. The conductors must be so proportioned that the energy transmitted 
through them will not cause an undue rise of temperature. 

2. The conductors must have such mechanical properties as to enable 
them to be successfully erected, and so durable as to require a minimum 
of annual maintenance. 

3. The conductors may be so designed as to entail a minimum first cost in 
line construction. 

92 



ECONOMICAL CONDITIONS. 93 

4. The conductors may be designed to attain a minimum first cost for 
station construction. 

5. The conductors may be so designed as to reduce first cost of plant, and 
cost of operation and maintenance to a minimum. 

6. The conductors may be designed to secure minimum total first cost of 
installation. 

7. The conductors may be so designed as to secure maximum conditions 
of good service. 

8. The conductors may be so designed as to attain a maximum of income 
with a minimum of station first cost." 

1. If cost of production of electric energy is low, and cost of conductors 
high, make conductors small in cross-section, and of such size that the in- 
terest on its cost plus the expense of maintaining it will be a minimum, and 
balance the cost of energy lost in heating. 

In no case, however, should the conductor be made of a size so small as to 
heat dangerously, for which see tables in " National Code." 

When the cost of electric energy is high, and that of the conductors low, 
then the cross-section of conductor must be larger, in order that the cost of 
energy lost may not- be too high ; but the balance, with that of interest and 
maintenance, should still be maintained. 

2. In all cases, conductors of sufficient size to have mechanical strength 
to suit the particular position they are to occupy, should be used. Due 
attention should be given to liability of snow and sleet, breaking of poles, 
etc., if conductors are overhead. 

3. When a plant is installed for a temporary purpose, and the line sal- 
vage will be small, while no harm will be done to the generating plant, the 
cost of the line should be a minimum, and the conductors may well be of a 
size just sufficient to carry the current with safety, both as regards heating 
and mechanical strength. 

4. The minimum first cost of station can be obtained, as far as influenced 
by the distribution system, by reducing the losses in the conductors to a 
minimum, thus calling for the smallest amount of current to do the work. 

5. As a decrease in the expenditure for line and construction demands an 
increase in the cost of central station, and apparatus for producing the 
extra energy lost in the line, and increases the operating expense of the 
station likewise, it is evident there must be a point where the total of 
the interest and depreciation on the line can be made practically equal to 
the cost of the energy lost in the line ; and at this point the expenses will 
be the least. Care must be used in applying this law, which was first stated 
by Lord Kelvin in 1881, as follows : " The most economical area of conductor 
will be that for which the annual interest on capital outlay equals the 
annual cost of energy wasted." One side of this equation would be the 
interest, depreciation, repairs, and maintenance of the conductor, the other 
would be the cost of producing the energy at the generator terminals, in- 
cluding interest, depreciation, and operating expense. 

Kapp says that the above law only applies where the capital outlay is 
proportional to the weight of metal contained in the conductor, a condition 
seldom obtaining in practice, and states the correct rule as follows : — 

" The most economical area of conductor is that for which the annual cost 
of energy wasted is equal to the annual interest on that portion of the cap- 
ital outlay which can be considered to be proportional to the weight of 
metal used." 

Prof. George Forbes, in his Cantor lectures in 1885, called that portion of the 
cost of the distributing system which is proportional to the weight of metal 
used, " the cost of laying one additional ton of copper ; " and he shows that, 
for a given rate of interest charge (inclusive of depreciation), and a given 
cost of copper, " the most economical section of the conductor is indepen- 
dent of the E.M.F., and of the distance, and is proportional to the current." 

Professor Forbes at the same time published some tables to facilitate the 
calculations ; and Prof. H. S. Carhart has enlarged them, and reduced the 
values to United States money. 



94 



CONDUCTORS. 



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96 



CONDUCTORS. 



The engineer first decides on what will he the cost of laying one additional 
ton of copper, and the rate of interest (+ depreciation) ; then, referring to 
the first table, he finds in the top line the amount corresponding to his cost 
of copper, and follows it down to the line corresponding to the rate of inter- 
est he is to charge ; and the number found at this intersection must then 
be taken to the second table, where, commencing on the line giving, at the 
left, the estimated cost of one electrical horse-power per annum, he follows 
to the right, stopping at the number nearest in value to that determined 
from the first table. At the top of this column will be found the area in 
circular mils and in square inches of the most economical conductor for 100 
amperes of current, and size for other currents is in proportion. 

The preceding rule determines the most economical cross-section of con- 
ductor for a maximum current, and not for the varying current of practice ; 
therefore it is necessary to multiply the result obtained from the previous 
tables by a ratio found in the following table, which was also calculated by 
Professor Forbes from the following formula : — 



Mean current recurrent = 






where t % , t 2 , t a , t 4 represent the number of hours per annum during which 
one-quarter, one-half, three-quarters of the full current and the full current 
is respectively passing through the conductor. 

TO FIND MEAN ANNUAL CURRENT. 



Fraction of time per year 
during which 



is passing through the 
conductor. 












I 


t 











1 


1 





I 





\ 


I 





\ 


\ 



Ratio. 



1.000 
.944 
.901 
.884 
.875 
.838 
.820 
.810 
.790 
.771 



Fraction of time per year 
during which 



43 






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is passing through the 
conductor. 



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\ 
















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I 


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1 












1 





i 












Ratio. 



.760 
.744 
.729 
.718 
.685 
.661 
.650 
.611 
.586 
.545 



The figures in the columns headed, " \ current," " £ current," " £ current," 
and " Full current," represent fractions of the total annual time during 
which a, J, f- of the full current and the full current is passing through the 
conductor. 

The figures in the column headed " Ratio " are those with which the most 
economical area for the maximum current must be multiplied to obtain the 
most economical area for a varying current. 

The following table constructed under the direction of Professor Forbes, 
by the writer, Avill assist in approximate quick determinations, and can be 
used for any cost of power or copper. 

For example : What would be the most economical density of current for 
a line, Avith copper at 14 cents per pound, and power costing 19 dollars per 
horse-power per annum. 

Multiply the constant difference, .0406 in column h, by the cost of power, 
19 x .0406= .7714, and divide this result by the cost of copper in cents, 14, 

or -^=.0551. 

Now look in column/ of differences for the nearest number to this result. 



HORSE-POWER AT MOTOR-TERMINALS. 



97 



which is .0546 ; and to the left in the first column will be found 375 amperes 
per square inch. 
All other data can be calculated from the data given in the other columns. 

I. Horse-power at Motor-Terminals. ?.46 amperes at 
lOO volts, distance lOO© feet. 

Am. Inst. E.E. standard, pure, soft-drawn copper at 20° C; 1000 ft., 1 sq. in. 
weighs 3851.16 lbs.; R= .008129. 





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175 


.07460 
.05968 
.04973 
.04262 


574.58 
459.68 
383.06 
328.28 


$57,458 
45.968 
38.306 
32.828 


$2.8729 
2.2984 
1.9153 
1.6414 


.5745 
.3831 
.2739 


.01626 
.02032 
.02439 
.02845 


$.1626 
.2032 
.2439 
.2845 


101.626 
102.032 
102.439 
102.845 


1.626 

2.032 
2.439 

2.845 


200 

225 
250 
275 


.03730 
.03316 
.02984 
.02713 


287.28 
255.40 
229.84 
208.94 


28.728 
25.540 
22.984 
20.894 


1.4364 
1.2770 
1.1492 
1.0447 


.2050 
.1594 
.1278 
.1045 


.03252 
.03658 
.04065 
.04471 


.3252 
.3658 
.4065 
.4471 


103.252 
103.658 
104.065 
104.471 


3.252 
3.658 
4.065 
4.471 


300 

325 
350 
375 


.02486 
.02295 
.02131 
.01989 


191.52 
176.79 
164.14 
153.22 


19.152 
17.679 
16.414 
15.322 


.9576 
.8839 
.8207 
.7661 


.0871 
.0737 
.0632 
.0546 


.04878 
.05284 
.05691 
.06097 


.4878 
.5284 
.5691 
.6097 


104.878 
105.284 
105.691 
106.097 


4.878 
5.284 
5.691 
6.097 


400 

425 
450 
475 


.01865 
.01755 
.01658 
.01570 


143.64 
135.19 
127.70 
120.97 


14.364 
13.519 
12.770 
12.097 


.7182 
.6759 
.6385 
.6048 


.0479 
.0423 
.0374 
.0337 


.06504 
.06910 
.07317 
.07723 


.6504 
.6910 
.7317 
.7723 


106.504 
106.910 
107.317 
107.723 


6.504 
6.910 
7.317 
7.723 


500 

525 
550 
575 


.01492 
.01420 
.01356 
.01297 


114.92 

109.44 

104.47 

99.93 


11.492 
10.944 
10.447 
9.993 


.5746 
.5472 
.5223 
.4996 


.0302 
.0274 
.0249 
.0227 


.08130 
.08536 
.08942 
.09348 


.8130 
.8536 
.8942 
.9348 


108.130 
108.536 
108.942 
109.348 


8.130 
8.536 
8.942 
9.348 


600 

625 
650 
675 


.01244 
.01193 
.01147 
.01105 


95.76 
91.93 
88.39 
85.12 


9.576 
9.193 
8.839 
8.512 


.4788 
.4596 
.4419 
.4256 


.0208 
.0192 
.0177 
.0163 


.09756 
.10162 
.10568 
.10974 


. .9756 
© 1.0162 
S 1.0568 

1 1.0974 

CD 


109.756 
110.162 
110.568 
110.974 


9.756 
10.162 
10.568 
10.974 


900 

725 
750 
775 


.01066 
.01029 
.00995 
.00962 


82.08 
79.25 
76.61 
74.14 


8.208 
7.925 
7.661 
7.414 


.4104 
.3962 
.3830 
.3707 


.0152 
.0142 
.0132 
.0123 


.11382 
.11788 
.12194 
.12600 


g 1.1382 
g 1.1788 
£ 1.2194 
3 1.2600 


111.382 
111.788 
112.194 
112.600 


11.382 
11.788 
12.194 
12.600 


soo 

825 
850 

875 


.00933 
.00905 
.00878 
.00854 


71.82 
69.64 
67.59 
65.66 


7.182 
6.964 
6.759 
6.566 


.3591 
.3482 
.3379 
.3283 


.0116 
.0109 
.0103 
.0096 


.13008 
.13414 
.13820 
.14226 


| 1.3008 
■g 1.3414 
R 1.3820 
O 1.4226 


113.008 
113.414 
113.820 
114.226 


13.008 
13.414 
13.820 
14.226 


ooo 

925 
950 
975 


.00829 
.00807 
.00785 
.00766 


63.84 
62.12 
60.48 
58.93 


6.384 
6.212 
6.048 
5.893 


.3192 
.3106 
.3024 
.2946 


.0091 
.0086 
.0082 
.0078 


.14634 
.15040 
.15446 
.15852 


1.4634 
1.5040 
1.5446 
1.5822 


114.634 
115.040 
115.446 
115.852 


14.634 
15.040 
15.446 
15.852 


lOOO 


.00746 


57.46 


5.746 


.2873 


.0073 


.16258 


1.6258 


116.258 


16.258 



Res. of 1000 ft., 1 sq. in. at 
80° C. = . 010,0678. 



98 CONDUCTORS. 

6. When a plant is installed for more or less temporary work, it is, of 
course, policy to make the first cost a minimum ; and again, in many places, 
and perhaps in most places, it is impossible to predetermine the cost of 
power per unit, or number of hours it will be necessary to run, or the num- 
ber of hours of heavy and of light load, and many other items necessary to 
be known in order to determine and calculate the most economical form of 
plant to install. 

In such cases it is often necessary to feel one's way by installing a plant of 
low cost until the market is developed or its direction detei-mined, after 
which it is much easier to lay out a plant that will produce the most econom- 
ical results. 

Sprague says that the least cost of plant is determined when the variation 
in the cost of the generator is equal to that in the cost of the line ; Avhich is 
practically true, provided the cost of motors and generators per horse-power 
or unit capacity is the same. Sprague then develops the following law : — 

" With fixed conditions of cost and of efficiency of apparatus, the number 
of volts fall to get the minimum cost of plant, is a function of distance 
alone, and is independent of the E.M.F. used at the motor." 

" With any fixed couple and commercial efficiency, the cost of the wire 
bears a definite and fixed ratio to the cost of the generating plant." 

" The cost of the wire varies directly with the cost of the generating 
plant." 

" If we do not limit ourselves in the E.M.F. used, the cost per horse-power 
delivered exclusive of line erection is, for least cost and for a given commer- 
cial efficiency, absolutely independent of the distance." 

Without going into the detail, if we work out problems based on the above 
laws, the result shows that the law first stated by Professor Forbes, i.e., that 
" the most economical section of conductor is independent of the distance 
or E.M.F., and is proportional to the current," is correct. 

Badt develops the following law : — 

" For minimum initial cost of plant, and assuming certain prices per 
horse-power of motors and generators and power plant (all erected and 
ready for operation), and assuming a certain price per pound for copper (de- 
livered at the poles), the total cost of the plant, excluding line construction, 
is a constant for a certain efficiency of the electric system, no matter what 
the E.M.F. of the motor and the distance may be." 

" At a given efficiency of the electric system, the E.M.F. of the motor and 
distance will increase and decrease in the same ratio." 

7. In designing for the accomplishment of the best service, series circuits 
can be economically laid out under some of the previous rules ; but in de- 
signing circuits for parallel distribution, they must be arranged for furnish- 
ing a constant and unvarying pressure at the lamps or motors of the 
customer, regardless of the cost of conductors ; and therefore service require- 
ments and not minimum first cost govern, as no service will be a paying 
investment that has not a uniform pressure and is not continuous in its 
character. 

Parallel distribution is fully treated in another chapter. 

8. It is the attempt of all engineers to attain a maximum income from a 
minimum first cost of plant. 

If power is cheap and transportation costly, it is better to construct plant 
under Section 3. In some cases, though, so much of the station capacity 
might be wasted in the conductors as to leave little from which an income 
could be received ; but increasing the carrying capacity of the conductors 
somewhat, provided it did not cost too much to accommodate the extra 
machinery, would enable a paying income to be made. 

In order to determine the proper relation of line to station and plant, it is 
necessary to study the prospective loads. If street-lighting by series arcs is 
to be one of the sources of income, then a study of the hours of lighting 
must be made, and all the data as to number of hours burning, etc., will be 
found in the chapter on lighting schedules. 

For parallel and other methods of distribution, it will be necessary for 
some one acquainted with the system to make the necessary examination of 
the territory, and determine from its nature the probable load-curves. 



CALCULATION OF SIZE OF CONDUCTORS. 



99 



Efficiency in Electric Power Transmission. 

From Badt's " Electric Transmission Hand-Book." 



1. 


2. 


3. 


4. 


5. 


6. 


a> a -^ 


^ 3 2 

i-h" i" a 
KG 


S3 

PM.S 


£a^' 

*-g a 


Mech. H.P. to 

be delivered 

at generator 

pulley. 


y 0Q <D 
k " H 


N. 




% 






I. 


1.00 
1.00 
1.00 
1.00 


1.1111 
1.1111 
1.1111 
1.1111 


0.0 
1.0 
2.0 
3.0 


1.1111 

1.1223 
1.1337 
1.1454 


1.2346 
1.2470 
1.2597 
1.2727 


81.00 
80.19 
79.38 

78.57 


1.00 
1.00 
1.00 
1.00 


1.1111 
1.1111 
1.1111 
1.1111 


4.0 
5.0 
6.0 
7.0 


1.1574 
1.1696 
1.1721 
1.1947 


1.2860 
1.2995 
1.3134 
1.3275 


77.76 
76.95 
76.14 
75.33 


1.00 
1.00 
1.00 
1.00 


1.1111 
1.1111 
1.1111 
1.1111 


8.0 
9.0 
10.0 
12.5 


1.2077 
1.2210 
1.2345 
1.2698 


1.3419 
1.3567 
1.3717 
1.4109 


74.52 
73.71 
72.90 
70.88 


1.00 
1.00 
1.00 
1.00 


1.1111 
1.1111 
1.1111 
1.1111 


15.0 
17.5 
20.0 
22.5 


1.3072 
1.3468 
1.3888 
1.4336 


1.4524 
1.4964 
1.5447 
1.5929 


68.85 
66.83 
64.80 
62.78 


1.00 
1.00 
1.00 
1.00 


1.1111 
1.1111 
1.1111 
1.1111 


25.0 
27.5 
30.0 
32.5 


1.4815 
1.5325 
1.5873 
1.6464 


1.6461 
1.7028 
1.7636 
1.8293 


60.75 
58.73 
56.70 
54.68 


1.00 
1.00 
1.00 
1.00 


1.1111 
1.1111 
1.1111 
1.1111 


35.0 
37.5 
38.3 
40.0 


1.7094 

1.7778 
1.8000 
1.8518 


1.8993 
1.9753 
2.0000 
2.0576 


52.65 
50.63 
50.00 
48.60 


1.00 
1.00 
1.00 
1.00 


1.1111 
1.1111 
1.1111 
1.1111 


42.5 
45.0 
47.5 
50.0 


1.9323 
2.0210 
2.1164 

2.2222 


2.1470 
2.2446 
2.3515 

2.4622 


46.58 
44.55 
42.53 
40.50 



CAICUUATION OF THE SIZE OE CONDUCTORS 
FOE CONTINUOUS CURRENTS. 



Parallel distribution : — 

Resistance of one mil-foot pure copper at"0° C = 9.59 ohms ; 
Temp, coefficient for 70° F. = 1.084 

Resistance of 1 mil-foot of pure copper at 70° F.= 10.395 ohms 
Resistance of 1 mil-foot of 96% conductivity 

copper wire at 70° F. r= 10.81 ohms ; 



L.ofC. 



100 CONDUCTORS. 

Resistance of a copper wire conductor is then equal to 
Length in feet x 10.81 



dia.s =tf.ohms. (1) 



and the cross-section in circular mils or 



For lamps : — 



dia. 2 = Length in feet x 10.81 ^ 

Resistance ' 



Let w — watts per candle-power ; 

then candle-power x w = watts per lamp, = W '■' 

and if E = voltage, or P.D. of circuit ; 

W 
then — = i = current in amperes per lamp. 

A voltage at which lamps are to he run is usually assumed, and a drop or 
loss of pressure of a certain percentage of this, determined on, and all wiring 
is calculated with those points as data. For instance, the most common 
voltage is 110 or thereabouts, and 5% drop, or 5.5 volts, is commonly assumed 
as the loss in pressure ; then the size of wire to produce this drop, with a 
given number of lamps, N, taking, say, I amperes will be 

10.81 x 2 distance x / ,. , . , ., „ 

rr — -= -— — dia. 2 , or circular mils of copper. (3) 

volts drop 5.5 ' ^ v ' 

For example : 120 lamps taking .5 amp. each are to be wired at a distance 
of 60 feet from the dynamo to the centre of distribution, at a drop of 3 volts. 

_,. 10.81 x 2 x 60 7 x 60 amps. ___. . . .. „ _ _ , _ 

Then, — ±— =25944 cir. mils, or No. 6 B. and S. 

3 volts. ' 

If the hot resistance of one lamp be given, and the number of lamps and 
distance, with the percentage of loss, then 

., 10.81 x 2 distance x no. of lamps 100 ... 

cir. mils = — — ~ = z- x =-. — ■ • (*) 

Resistance of one lamp % loss 

Example : — Take the same case as above : 120 lamps ; distance 60 feet ; 
drop in circuit, 3 % ; hot resistance of lamp, 200 ohms. 

10.81 X 2 X 60 / X 120 100 rtB ... . ., 
Then, /A X -s~ = 25944 cir. mils. 

For motors : — 

1 Electric horse-power = 746 watts. 
Therefore, horse-power x 746 = watts. 
And watts -J- volts = amperes. 
Let 2?= volts at terminals of motor. 
v z= volts lost in conductor. 
2? + v = E.M.F. at generator terminals. 

7= current required at motor to deliver iVmechanical h.p. at shaft 

of motor. 
D= single distance between motor and generator. 
A r = number of mechanical h.p. delivered at motor shaft. 
A = area of cross-section of conductor in cir. mils. 
i2 = conductor resistance both ways. 
wt = weight in pounds of conductor copper. 
m% = commercial efficiency of motor. 
g % = commercial efficiency of generator. 
I %=. commercial efficiency of whole system. 
c% = per cent of energy lost in conductor, 
all % expressed as a decimal, as, 90 % = .90, 

N 
Then, —^ — electrical horse-power delivered at motor terminals ; 

m% 

and J =¥3nS £ = amperes. (5) 

By formula No. 1, R = ^ — '- — = resistance of conductor both ways. 



Or, reducing R : 



SIZES OF CONDUCTORS. 101 

D X 21.62 



A 
The drop or loss in the line v=zl R, or 

„ = IX7>-X 21.62. (6) 

and i = fxJxM - e2 . (7) 

Substituting the value for /, 

. 746 X-^X-^X 21.62 

we have, A = ^ — ^ ; (8) 

^ X »i% X v ' w 

, , . . 16128.5 xNX-D 

and reducing we have, — - ^ . 

& ' Exm%xv 

Example : — 

Motor 20 h.p. m% =90%. 
Volts at terminals = 500. 
Distance =200 ft. 

Loss in conductors = 5 %. 

Then, E.M.F. of generator = ^— = 526.3 volts, 
and drop in line, v = 526.3 — 500 = 26.3 ; 

t> i-v * i «v r 746 ^ t 746X20 OD 

But by formula (5), /= ^-^ , or I = ^^ = 33 amperes ; 

and the National code only allows 8 amperes for No. 16, and 33 amperes 
would need at least No. 10 wire. 

The volts drop and per cent loss in No. 10 B. and S. wire, required to carry 
the 33 amperes as above shown, will be found as follows : — 
R of No. 10 B. and S. = .0009972 per foot ; 
R of 400 ft. = .39888 ohms ; 
Volts drop = IR = 33 X 39888 = 13.16 volts ; 
Volts at generator =500+ 13. = 513. 

13 
Per cent drop = — — = 2.5 %. 
olo 

SIZES OF CONDUCTORS FOtt HTCA»DE§CEJfT 
CIHCUITI. 

(By W. D. Weaver.) 

The most accurate method of determining the proper sizes of incandescent 
lamp conductors is to refer all measurements back to the dynamo, converter, 
or street tap. 

To illustrate, suppose we have an installa- 
tion of 150 lights, consisting of a feeder or 
dynamo main 20 feet long (to distributing 
point), and several mains, A, B, and C, their 
lamps and lamp centres being respectively 
60, 50, and 40 in number, and 38, 60, and 90 
feet from the end of the feeder. Let us ' — c 

calculate the sizes of the feeder and one 4m 

main, and of one branch having 12 lamps, centre, a 
with centre 20 feet from the main, the 
branch starting 18 feet from the distribut- s 

ing point. (See cut.) "Fig. 1. 

To find the size of the branch wire, refer 
to the appropriate table with 20 + 18 + 20 
feet, or 58 feet for 12 lamps. 

To find the size of the main, imagine the branches on one side to be 
revolved (or lay them out thus on a diagram), so that all are on the same side 



I -1-4- -«b 5 -Sj 

mm 

1 A 



SS-18-lo 



102 CONDUCTORS. 



of the main ; then estimate or calculate the lamp centre of the resultant group, 
which in this case Ave will suppose to be 23 i'eet from the main, and 38 feet 
from the distributing point measured along the main, and refer to the table 
with 20 + 38+23 feet for 12 + 30+18 lamps, or 81 feet for 60 lamps. 

To find the size of the feeder, suppose the mains to be revolved about the 
distributing point so that they all overlap, and with all the branches on one 
side of the overlapping mains ; then estimate or calculate the lamp centre 
of the resultant group (comprising all the lamps), which in this case we will 
suppose to be 20 feet from the overlapping mains measured at right angles, 
and 48 feet from the distributing point measured along the main, and refer 
to the table with 20 + 48 + 20 feet, or 88 feet for 150 lights, or for the largest 
number of lights that will ever be used at one time. 

In simple cases the quantities may be estimated either directly (especially 
for branches) or from rough diagrams ; and for more complex cases, or where 
a perfectly accurate result is desired, the following rules are given : — 

For Branches, follow the method given above. 

For M ain.<*. multiply the number of lamps on each branch of a main by 
the distance of their lamp centre from the distributing point, always meas- 
ured along the lead, of the main and branch; add the products thus obtained 
for all the branches on the main, and divide by the whole number of lamps 
on the branches. Add the length of feeder, and refer to the table with the 
resultant distance and lamps. 

Example : — (See cut, main A.) 

(18 + 20) X 12= 456 
(33 + 30) X 30 = 1890 
(60 + 15) X 18 = 1350 
456 + 1890 + 1350 , OA . . , . an . 
12+ 30 + 18 + 20 = 81 feet for 60 lam P s - 

For feeders, add the sum of the products obtained as above for all 
the mains, divide by the entire number of lamps on the feeder, add the 
iength of the feeder, and refer to the table with this distance and all the 
lamps on the feeder, or the largest number that will ever be used at one time. 
Example : — (See cut.) 

Main A. 456 + 1890 + 1350 = 3696 
Main B. 60 X 50 =3000 

Main C. 90 X 40 =3600 

3696 + 3000 + 3600... .. „ , „ ... . 
' — ' 1- 20 = 88 feet for 150 lamps. 

Care must be taken not to confound a lamp centre (so-called) with a geo- 
metrical centre. For example, suppose a series of branches of equal length 
radiating from the end of a main like the spokes of a wheel, and having 
lamps at equal intervals. Here the geometrical centre is the radiating 
point, while the lamp centre is on a circle passing through the centres of 
the various groups, or the length of the radius from the radiating point. In 
the case of the main A given above, the geometrical centre is 15 feet from 
the main, while the true lamp centre is 23 feet. It is to preclude the error 
of geometrical centres that the branches and mains are laid down, or ima- 
gined, revolved. 

Sul»-1»raiiclies and Taps may in general be considered as groups of 
lamps directly on the branch itself, and thus included in the calculation for 
the branch. 

The above method is applicable to all systems of wiring, and is particularly 
valuable and economical in securing proper distribution of light on low volt- 
age circuits having a small percentage of loss. By stringing the branches 
first, when possible, this method may be easily followed without the aid of 
a diagram, even in complex cases. With the "closet" system of wiring, 
diagrams and calculations as a rule will not be required. 

The " tree" system of wiring is to be avoided where possible, on account 
of the unequal distribution of light it entails. In many cases, secondary 
centres of distribution may be substituted ; and if carefully calculated, the 
weight of wire in the latter case need not exceed that in the former. 

The voltmeter should always be connected with the centre of distribution, 
and not with the feeder near the dynamo, unless it is desirable to have a 
steady light in a particular locality, when it should be connected with the 
line there. 









CALCULATION OF SIZE. 



103 



Owing to the exceedingly small current passing through a voltmeter, the 
resistance of even a very small wire in ordinary cases will not practically 
affect its readings. Where the line is very long, a No. 12 or 14 insulated, 
iron wire may be used, and the voltmeter at the dynamo set once for all by 
comparison with a standard voltmeter temporarily attached at the point 
which is to be maintained at a constant potential. 



CALCULATION OF THE SIZE OF CONDUCTORS 
FOR ALTERNAIOG CURRENT CIRCUITS. 

When alternating currents first came into use, it was customary to calcu- 
late the sizes of conductors by the ordinary rules used in connection with 
direct currents. This did very well as long as small currents were in use, 
and distances were comparatively short ; but before long new effects began 
on the lines that were unaccountable to any one not familiar with the action 
of such currents in a conductor, and this led to a more thorough study of the 
problems. 

Briefly stated there are, besides the ohmic resistance of the copper, the 
following effects, due to the use of alternating currents : — 

Skin effect, a retardation of the current due to the property of alternating 
currents of apparently flowing along the outer surface or shell of the con- 
ductor, thus not making use of the full area. 

Inductive effects, a, self -induction of the current due to its alternations, in- 
ducing a counter E.M.F. in the conductor ; and b, mutual inductance, or the 
effect of other alternating current circuits. 

Capacity Effects, due to the fact that all lines of conductors act as electri- 
cal condensers, which are alternately charged and discharged with the 
fluctuations of the E.M.F. 

Skin Effect. 

The increase in resistance due to skin effect can be found by the use of the 
following table : — 

Skin Effect Factors, for Conductors carrying* Alternating- 
Currents. 

Note. — For true resistance, multiply ohmic resistance by factor from 
this table. 



Diam. 
and 


Frequencies. 


B.&S. 






















gauge. 


15 


20 


25 


33 


40 


50 


60 


80 


100 


130 


2" 


1.111 


1.160 


1.265 


1.405 


1.531 


1.682 


1.826 


2.074 


2.290 


2.560 


If 


1.072 


1.114 


1.170 


1.270 


1.366 


1.495 


1.622 


1.841 


2.030 


2.272 


n 


1.042 


1.064 


1.098 


1.161 


1.223 


1.321 


1.420 


1.610 


1.765 


1.983 


H- 


1.019 


1.030 


1.053 


1.084 


1.118 


1.176 


1.239 


1.374 


1.506 


1.694 


V' 


1.010 


1.019 


1.035 


1.059 


1.080 


1.124 


1.168 


1.270 


1.382 


1.545 


1.005 


1.010 


1.020 


1.038 


1.052 


1.080 


1.111 


1.181 


1.263 


1.397 


r 


1.002 


1.002 


1.007 


1.014 


1.016 


1.028 


1.040 


1.066 


1.100 


1.156 


0000 


1.001 


1.001 


1.002 


1.005 


1.006 


1.007 


1.008 


1.011 


1.022 


1.039 






1.001 


1.003 


1.005 


1.005 


1.006 


1.010 


1.015 


1.027 


000 








1.001 


1.002 


1.002 


1.005 


1.007 


1.010 


1.017 


00 










1.001 


1.001 


1.002 


1.004 


1.006 


1.010 

















1.001 


1.002 


1.005 


1.008 


1 
















1.001 


1.002 


1.005 


2 


















1.001 


1.002 


3 




















1.001 


4 




















1.000 



104 



CONDUCTORS. 



For other frequencies, Emmet gives the following table : — 



Product of Cir. Mils 
by Cycles per sec. 

10,000,000 

20,000,000 

30,000,000 

40,000,000 

50,000,000 

60,000,000 

70,000,000 

80,000,000 

90,000,000 
100,000,000 
125,000,000 
150,000,000 



Factor. 

1.00 
1.01 
1.03 
1.05 
1.08 
1.10 
1.13 
1.17 
1.20 
1.25 
1.34 
1.43 



EFFECTIVE OR ENERGY E.M.F. 

Fig. 2. 



Factors in the above table multiplied by the resistance in ohms will give 
the resistance of circular copper conductors to alternating currents. 

Effects of Self-induction. — Owing to the periodic variations of 
current in alternating-current circuits, a counter E.M.F. is set up, which 
does not coincide with the current, and which is not continuous, but periodic ; 
and, owing to the fact that such E.M.F. is the strongest when the current is 
increasing or decreasing most rapidly, the counter E.M.F. differs in phase 
with the current by 90°. 

If tbere be no inductive effect in a circuit (without considering anything 
else at present), the current produced by an impressed E.M.F. would be in 
phase, and the watts would be, as in direct currents, the product of the 
E.M.F. and current. Taking into account the inductive effect, the current 
is never in phase with the impressed E.M.F., and the watts are therefore 
never equal to the product of the two, but are less, according to the angle 
of phase difference ; and if they could be in quadrature, the product would 
be zero. 

The E.M.F. impressed on the circuit may be 
said to be made up of two components, one in 
phase with the current, as in direct currents, 
and the other in quadrature with it, as shown 
below in a right-angle triangle. 

Counter or inductive E.M.F. varies with the 
frequency of alternations ; but if the out-going 
and returning wires are close together, there is 
little induction ; if wound in a coil, the self-induction is much increased, 
and if an iron core be introduced into the coil, the flux is very much in- 
creased, and therefore tbe self-induction. 

Impedance. —In a plain, alternating-current circuit without iron, the 
current due to a given E.M.F. will depend upon a resistance which is the 
resultant of two components : its resistance as in 
direct currents, and its inductive resistance, or 
the current divided into the inductive E.M.F. 
These two components are compounded at right 
angles, and the resultant is called impedance, and 
can be represented by the same triangle as was 
used to illustrate the two E.M.F. 's and their 
resultant. 

Impedance also varies with the rate of alternations the same as does the 
counter or inductive E.M.F. 

If we have a circuit including a number of parts 
in series, each having a different angle of lag, and 
represented as below by different triangles joined 
together, it will be seen that the sum of all the 
E.M.F.'s impressed upon the parts or impedances 
is greater than the E.M.F. impressed upon the 
whole circuit ; and in order to arrive at the latter 
value, it is necessary to lay out each case sepa- 
rately, all the horizontal lines representing energy 



NERGY RESISTANCE 

Fig. 3. 




TOTAL ENERGY E.M F. 

Fig. 4. 



CALCULATION OF SIZE. 



105 



E.M.F.'s (or resistances), and all the vertical lines representing inductive 
E.M.F.'s (or resistances, now called reactances). 

To find the impedance equal to two impedances in parallel, construct a 
parallelogram, the adjacent sides of which will 
De the reciprocals of their values ; the diagonal 
of this parallelogram will be the reciprocal of 
the value of the resulting impedance ; and, as 
the lines representing the given impedances are 
joined at the proper phase angle with eacb other, 
the direction of the diagonal will represent the 
resulting phase. 

In the above figure -p= = J. 




1 

AC 



Fig. 5. 




-j— = AD = 1.3 ohms. 
Ax 

If two impedances, connected in parallel, have such values as to give a 

phase difference of 90°, i.e., are at right angles with each other, their result- 
ant value can be found by constructing a right- 
angle triangle, whose adjacent sides represent 
in direction and length the values of the two 
impedances in parallel. Join the two ends, 
and a line drawn from this hypothenuse at 
right angles and meeting the others at their 
junction, will be equal to and in the direction 
of the resultant value. 
■piQ g If etc and ce are two impedances in parallel, 

with a difference in phase of 90°, then cd equals 

in direction and in length the resultant of the two. 
Capacity Effects. — A condenser connected in multiple across the 

leads of an a.c. circuit is charged as the E.M.F. 

rises, and discharged as the E.M.F. falls, thus 

returning E.M.F. to the line just at the time 

that the inductive E.M.F. is opposing the line 

E.M.F., and both can be so arranged as to neu- 
tralize each other, or enough capacity can be 

introduced to cause a negative lag-angle, as shown 

in the following figure. 
When a condenser or a line having capacity is 

subjected to an alternating E.M.F., current will 

flow in to fill the capacity equal to Ex Cx «, 

where E is the E.M.F., C, the capacity in farads, and w = 2n JV. 
Thus, if a line has a capacity of 3 micro-farads, i? = 2000 volts, and jV = 30, 

then — 



ENERGY E.M.F. 




Fig. 7. 



Amperes J= 



1,000,000 



X 2000 X 30 X 6.28 = 1.1304. 



And a condenser may be said to have a reactance of -^- • 

This reactance is also in quadrature with the energy E.M.F., as is the in- 
ductive reactance, but acting in the opposite direction to that of the induc- 
tance ; and may therefore be so arranged as to neutralize it. Line capacity 
acts like a condenser placed in multiple at the middle point of the length 
of the line. 

Lag angles and power factors of alternating-current motors of the induc- 
tion type vary with the load they carry and with the design and size, some 
of large size having power factors as high as 97% at full load, while poorly 
designed motors may have but 75% or less. 

Synchronous motors run with a separately excited field, which may be so 
varied as to produce a leading or lagging current, or be made to take from or 
return energy to the line. When running with but little load, with field cur- 
rent high, energy will be absorbed from the line as the impressed E.M.F. 



106 



CONDUCTORS. 



rises, and returned to the line as it falls, thus acting like a condenser, and 
tending to steady the E.M.F. of the circuit, which may be disturbed and 
lowered by the inductance of induction motors. 

Closed circuit transformers with secondary open have a power factor of 
about 70%, and when loaded with non-inductive load, large sizes have a 
power factor of over 99%, with an induction component of say 6%, even at 
half-load the power factor is over 99%. 

In the ordinary alternating-current lighting circuits, the elements are, the 
lamps, the secondary circuits, the transformers, the primary mains, and 
feeders. 

If distances are considerable and the wires large, there will be some in- 
duction due to the primary and secondary mains ; but most of the effect will 
come from the transformer, provided, of course, that nothing but incandes- 
cent lamps are used as load on the secondary. With good-sized transformers, 
the total power factor will be above 99%. 

In the following table will be found the angles of lag, together with the 
power-factors and factors of induction due to each, from which may be com- 
puted the effects on lines of different inductances. 



Power Factor.*! and Induction Factor* for Different 
Angles of Lag*. 



bCCS 

o 




00 r- ' 
o fl o 


o . 




CO - 

'" i s 

o S.o 


°« 

bud 

r 


^ CO 


2 , fl 


® bo 

afi 


o 2 


cfl.o 


fi£ 


<D 


«B 


■ ■'>"-■ 


<a> 


<a> 


I o 3 


<3i 


<35 


■ 03 


q> 


«a 


b 


a 


0) <D 

fig 


on 

o 


a 


fi£ 


CO 

O 


a 


fi£ 


cg 
O 


a 


on 


O 


rn 


be 


O 


m 


be 


o 


OQ 


fee 


a 


53 


1 


.9998 


.0174 


24 


.9135 


.4067 


46 


.6946 


.7193 


69 


.3584 


.9336 


2 


.9994 


.0349 


25 


.9063 


.4226 


47 


.6820 


.7313 


70 


.3420 


.9397 


3 


.9986 


.0523 


26 


.8988 


.4384 


48 


.6691 


.7431 


71 


.3256 


.9455 


4 


.9976 


.0698 


27 


.8910 


.4540 


49 


.6561 


.7547 


72 


.3090 


.9511 


5 


.9962 


.0872 


28 


.8829 


.4695 


50 


.6428 


.7660 


73 


.2924 


.9563 


6 


.9945 


.1045 


29 


.8746 


.4848 


51 


.6293 


.7771 


74 


.2756 


.9613 


7 


.9925 


.1219 


30 


.8660 


.5000 


52 


.6156 


.7880 


75 


.2588 


.9659 


8 


.9903 


.1392 


31 


.8572 


.5150 


53 


.6018 


.7986 


76 


.2419 


.9703 


9 


.9877 


.1564 


32 


.8480 


.5299 


54 


.5878 


.8090 


77 


.2249 


.9744 


10 


.9848 


.1736 


33 


.8387 


.5446 


55 


.5736 


.8191 


78 


.2079 


.9781 


11 


.9816 


.1908 


34 


.8290 


.5592 


56 


.5592 


.8290 


79 


.1908 


.9816 


12 


.9781 


.2079 


35 


.8191 


.5736 


57 


.5446 


.8387 


80 


.1736 


.9848 


13 


.9744 


.2249 


36 


.8090 


.5878 


58 


.5299 


.8480 


81 


.1564 


.9877 


14 


.9703 


.2419 


37 


.7986 


.6018 


59 


.5150 


.8572 


82 


.1392 


.9903 


15 


.9659 


.2588 


38 


.7880 


.6156 


60 


.5000 


.8660 


83 


.1219 


.9925 


16 


.9613 


.2756 


39 


.7771 


.6293 


61 


.4848 


.8746 


84 


.1045 


.9945 


17 


.9563 


.2924 


40 


.7660 


.6428 


62 


.4695 


.8829 


85 


.0872 


.9962 


18 


.9511 


.3090 


41 


.7547 


.6561 


63 


.4540 


.8910 


86 


.0698 


.9976 


19 


.9455 


.3256 


42 


.7431 


.6691 


64 


.4384 


.8988 


87 


.0523 


.9986 


20 


.9397 


.3420 


43 


.7313 


.6820 


65 


.4226 


.9063 


88 


.0349 


.9994 


21 


.9336 


.3584 


44 


.7193 


.6946 


66 


.4067 


.9135 


89 


.0174 


.9998 


22 


.9272 


.3746 


45 


.7071 


.7071 


67 


.3907 


.9205 








23 


.9205 


.3907 








68 


.3746 


.9272 









Inductive Resistance of lines. — As previously stated, two par- 
allel wires carrying alternating currents induce in each other counter or in- 
ductive E.M.F.'s that tend to retard the flow of current. The closer together 
these wires are, the less is this effect, and the more nearly the current waves 
are to the simple harmonic curve, the less is the retardation. 

The counter E.M.F. is somewhat larger for small wires than for large, 



INDUCTANCE FACTORS. 



107 



provided the current and distance between centres be the same, and the 
effect is about 150 times greater in iron wire circuits than with copper, as 
will be seen by reference to the following formulae, by which both are cal- 
culated. 

ODUCTAUfCE FACTOR!. 

In Tables I. and II. below are given the formuhe for inductance of two 
parallel wires of copper and of iron ; and in Table III. the inductance per 
mile for two copper wires has been computed for different inter-axial dis- 
tances. 



Table I. — Inductance for Parallel Copper l^ires. 



Formula, 



Then 



d = distance apart, centre to centre, of wires. 

r = radius of wires. 

Z = inductance of each wire in millihenrys. 

L — |.5 + ^2 log 6 - )]l<>- 6 , Per centimeter. 

L per centimeter =.000,000,5 -f .000,004,6 log— 
L per inch = .000,001,27+ .000,011,68 log- 

L per foot = .000,015,24 + .000,14 log - 

L per 1,000 feet =.01524 +.14 log — 

L per mile =.0805 +.741 log- 



Table II.— Inductance for Parallel Iron Wires* 



Formula, 



d = distance apart, centre to centre, of wires. 

r= radius of wires. 

i = inductance of each wire in millihenrys. 



L = [75. + (2 log e - \ 1 10- 6 , per centimeter. 
L per centimeter = .000,075 + .000,004,6 log °- 



L per inch = .000,191 + .000,011,68 log - . 

L per foot = .002,286+ .000,14 log - . 

L per 1,000 feet = 2.286 + .14 log - . 

r 



L per mile 



= 12.070 +.741 



log 



108 



CONDUCTORS. 



Tahle III. — Inductance in Millihenry's, per Mile, for 
each of Two Copper Wires Parallel to each other. 







Interaxial Distance in Inches. 




B. and S. 










gauge. 
















3. 


6. 


12. 


24. 


36. 


48. 


0000 


0.907 


1.130 


1.353 


1.576 


1.707 


1.799 


000 


0.944 


1.168 


1.391 


1.614 


1.745 


1.836 


00 


0.982 


1.205 


1.425 


1.651 


1.784 


1.874 





1.019 


1.242 


1.465 


1.688 


1.818 


1.911 


1 


1.056 


1.280 


1.502 


1.725 


1.856 


1.949 


2 


1.094 


1.317 


1.540 


1.764 


1.893 


1.986 


3 


1.131 


1.354 


1.577 


1.800 


1.931 


2.023 


4 


1.168 


1.392 


1.614 


1.838 


1.968 


2.061 


5 


1.206 


1.429 


1.652 


1.875 


2.005 


2.099 


6 


1.243 


1.466 


1.689 


1.912 


2.043 


2.135 


7 


1.280 


1.503 


1.727 


1.949 


2.079 


2.172 


8 


1.317 


1.540 


1.764 


1.986 


2.117 


2.209 


9 


1.355 


1.578 


1.801 


2.025 


2.155 


2.248 


10 


1.392 


1.615 


1.838 


2.061 


2.192 


2.285 


11 


1.429 


1.652 


1.875 


2.099 


2.229 


2.322 


12 


1.467 


1.690 


1.913 


2.135 


2.266 


2.359 



Inductance in Millihenrys per lOOO feet of Copper 
Circuit. 

2 AERIAL WIRES. 



Interaxial 
Distance. 


1" dia. 


f" dia. 


\" dia. 


B. and S. 
0000 


000 


00 





3" 


.248 


.283 


.333 


.344 


.358 


.373 


.386 


6 


.333 


.369 


.417 


.428 


.442 


.456 


.471 


12 


.417 


.451 


.500 


.513 


.527 


.540 


.555 


24 


.500 


.538 


.587 


.597 


.611 


.625 


.640 


48 


.587 


.621 


.671 


.681 


.695 


.710 


.724 



Interaxial 
Distance. 


>• 


2. 


3. 


4. 


5. 


6. 


7. 


8. 


9. 


10. 


3 // 


.400 


.415 


.429 


.442 


.457 


.472 


.484 


.499 


.513 


.527 


6 


.485 


.498 


.513 


.527 


.541 


.555 


.570 


.583 


.597 


.612 


12 


.570 


.583 


.597 


.612 


.626 


.640 


.654 


.668 


.683 


.696 


24 


.654 


.668 


.682 


.696 


.711 


.724 


.738 


.753 


.767 


.781 


48 


.738 


.752 


.767 


.781 


.795 


.808 


.823 


.837 


.851 


.865 



Formula 



( - 5 + 1 0gr ) I10- 6 :=millihenrys 



per centimeter ; 



and 



.015244- .14 log - = millihenrys per 1000 ft. of copper Avire. 

Inductive resistances 
2 it n x millihenrys from above table 



1000 



henrys per 1000 feet of circuit. 



Inductive drop = current x inductive resistance. 



INDUCTANCE OF THREE-PHASE SYSTEM. 



109 



HVOTTCTAHTCE I*EI1 BEEEJB OF CIRCUIT THREE- 
PHASE SYSTEM, GO p. p. s. 

(Dr. F. A. C. Perrine and Frank G. Baum in Trans. A. I. E. E.) 



DO 

M 

2 
CO 


5 

-S CO 

CD 0) 

§ § 
5 M 


<D so 

hi 
s 3 


CO * 


-g x<° § 

5 -§ x s 


co 

da 

w 

CD 
N 

bo 


CD 

4J CO 

Jrs 


0> co 
O CD 

to £3 


CO * 


CD y 

§xo 


0000 


.46 


12 


.00234 


0.884 


4 


.204 


12 


.00280 


1.057 






18 


.00256 


.967 






18 


.00300 


1.133 






24 


.00270 


1.015 






24 


.00315 


1.189 






48 


.00312 


1.178 






48 


.00358 


1.351 


000 


.41 


12 


.00241 


.910 


5 


.182 


12 


.00286 


1.080 






18 


.00262 


.989 






18 


.00307 


1.159 






24 


.00277 


1.046 






24 


.00323 


1.220 






48 


.00318 


1.201 






48 


.00356 


1.344 


00 


.365 


12 


.00248 


.937 


6 


.162 


12 


.00291 


1.098 






18 


.00269 


1.016 






18 


.00313 


1.182 






24 


.00285 


1.076 






24 


.00329 


1.243 






48 


.00330 


1.246 






48 


.00360 


1.393 





.325 


12 


.00254 


.959 


7 


.144 


. 12 


.00298 


1.125 






18 


.00276 


1.042 






18 


.00310 


1.204 






24 


.00293 


1.106 






24 


.00336 


1.269 






48 


.00331 


1.250 






48 


.00377 


1.423 


1 


.289 


12 


.00260 


.983 


8 


.128 


12 


.00303 


1.144 






18 


.00281 


1.061 






18 


.00325 


1.227 






24 


.00298 


1.125 






24 


.00341 


1.288 






48 


.00338 


1.276 






48 


.00384 


1.450 


2 


.258 


12 


.00267 


1.008 


9 


.114 


12 


.00310 


1.171 






18 


.00288 


1.083 






18 


.00332 


1.253 






24 


.00304 


1.1*8 






24 


.00348 


1.314 






48 


.0C344 


1.299 






48 


.00389 


1.469 


3 


.229 


12 


.00274 


1.035 


10 


.102 


12 


.00318 


1.201 






18 


.00294 


1.110 






18 


.00340 


1.284 






24 


.00310 


1.171 






24 


.00355 


1.340 






48 


.00351 


1.335 






48 


.00396 


1.495 



Basis of Taole. 



'jab = 2 V§ 9 \jrj_j_- — self-ind. in C. G. S. units for loop a. b. (*per cm.) 
L 0.434 -1 

Lab = 0.000558 T2.303 log 10 (-\ + .25 1 L, in henrys. 



Inductive drop in loop ab = Lab X 2 -a x / X L. 

d = distance between wires (inch). 

r = radius of wire (inch). 

L = length of circuit in miles. 

f=z cycles per second. 

/= current in one wire. 

For self-induction of one wire divide Lab by V3. 



110 



CONDUCTORS. 



Inductive Resistance of Two Parallel Insulated Wire*. 

FREQUENCY 100. 





lnteraxial Distance. 


Diam. 


3// 


3// 


\\» 


3" 


6" 


12" 


24" 


48" 


B. & S. 
gauge. 


Ohms 


Ohms 


Ohms 


Ohms 


Ohms 


Ohms 


Ohms 


Ohms 


per 
1000 ft. 


per 

1000 ft. 


per 
1000 ft. 


per 
1000 ft. 


per 

1000 ft. 


per 
1000 ft. 


per 

1000 ft. 


per 
1000 ft. 




dist. 


dist. 


dist. 


dist. 


dist. 


dist 


dist. 


dist. 


2" 








.106 


.159 


.213 


.267 


.322 


u 








.128 


.182 


.236 


.290 


.344 


1 






.106 


.160 


.213 


.267 


.321 


.375 


1 






.128 


.182 


.236 


.290 


.344 


.398 


u 






.159 


.213 


.267 


.321 


.375 


.429 


0000 


.060 


.114 


.168 


.222 


.275 


.329 


.383 


.437 


000 


.069 


.123 


.177 


.230 


.284 


.338 


.392 


.446 


00 


.078 


.132 


.186 


.239 


.293 


.347 


.401 


.455 





.087 


.141 


.195 


.248 


.302 


.356 


.410 


.464 


1 


.096 


.150 


.203 


.257 


.311 


.366 


.419 


.473 


2 


.105 


.158 


.212 


.266 


.320 


.375 


.428 


.482 


3 


.114 


.167 


.221 


.275 


.329 


.384 


.437 


.491 


4 


.122 


.176 


.230 


.284 


.338 


.393 


.446 


.500 


5 


!l31 


.185 


.239 


.293 


.346 


.402 


.455 


.509 


6 


.140 


.194 


.248 


.301 


.355 


.411 


.464 


.518 


7 


.149 


.203 


.256 


.310 


.364 


.419 


.473 


.527 


8 


.158 


.212 


.265 


.319 


.373 


.428 


.482 


.536 


9 


.167 


.220 


.274 


.328 


.382 


.437 


.491 


.545 


10 


.176 


.229 


.283 


.337 


.391 


.446 


.500 


.554 



Inductive resistances at other frequencies are proportional to this tahle. 

CAPACITY OF CONDUCTORS. 

The following formulae have been developed by examination of the best 
authorities. 

Table I. — Capacity of Insulated lead-Protected Cables. 



A;r=specific inductive capacity of insulating material. Seepage 

table. 
D = diameter of cable outside of insulation. 
tf = diameter of conductor. 



for 



Microfarads per centimeter length, 
Microfarads per inch length, 
Microfarads per foot length, 
Microfarads per 1,000 feet length, 
Microfarads per mile length, 



.000,000,241,5.*. 
. D 

.000,000,613,4. k. 

. D 

log -a- 

.000,007,361. k. 



log 



I) 



d 
.007,361. k. 

l0S ~d- 
■038,83 k. 

i D 

log-,. 






CAPACITY OF CONDUCTORS. 



Ill 



Table II. 



Capacity of Siug-le Overhead Wires with 
Earth Return. 



ft = height above ground in mils or centimeters. 
d=z diameter of conductor in mils or centimeters. 

.000,000,241,5 



Microfarads per centimeter length, 



Microfarads per inch length, 



Microfarads per foot length, 



Microfarads per 1,000 feet length, 



Microfarads per mile length, 



. 4ft 
.000,000,613,4 



log 



4ft 



d 
.000,007,361 



log 



4ft 



d 

.007,361 
4ft 
d' 

.038,83 
. 4ft 



log 



Table III. — Capacity of each of Two Parallel Bare 
vErial Wires. 

D = distance apart from centre to centre. 
r= radius of wire = \ of diameter. 

.000,000,120,8 
Microfarads per centimeter length, 



Microfarads per inch length, 



Microfarads per foot length, 



Microfarads per 1,000 feet iength, 



Microfarads per mile length, 



log-- 
.000,000,306,7 
log- • 
.000,003,681 
log-- 
.003,681 



log-. 
.019,42 



log- 



Capacities per 1,000 ft. of Copper Circuit, 3 Wires. 

AERIAL. MICROFARADS. 



Interaxial 
distance, 
inches. 


1" dia. 


f" dia. 


i"dia. 


B. and S. 

0000 


000 


00 





3 
6 
12 

24 

48 


.00946 

.00682 

.005326 

.00436 

.00371 


.00815 

.00611 

.00489 

.004075 

.003492 


.00682 

.005326 

.00436 

.00371 

.00322 


.0066 

.0052 

.00428 

.00364 

.00317 


.00631 
.00502 
.00416 
.00356 
.00311 


.00605 
.00485 
.00404 
.00347 
.00304 


.00581 
.00469 
.00393 
.00339 
.00298 



112 



CONDUCTORS. 



Capacities per 1,000 ft. of Copper Circuit. 2 Wires. 

(Continued.) 





1. 


2. 


3. 


4. 


5. 


6. 


7. 


8. 


9. 


10. 


m' 






















3 


.005585 


.005375 


.00518 


.00501 


.00484 


.00468 


.00454 


.00441 


.004275 


.00416 


6 


.004545 


.00441 


.00428 


.00415 


.00404 


.00393 


.00383 


.00374 


.00364 


.003555 


12 


.00383 


.00374 


.00364 


.00355 


.00347 


.00339 


.00331 


.00324 


.00317 


.00310 


24 


.00331 


.00324 


.00317 


.00310 


.003035 


.00298 


.00292 


.00286 


.00281 


.00275 


48 


.00292 


.002865 


.00281 


.00275 


.00271 


.00265 


.00261 


.00256 


.00251 


.00247 



Capacity and Self-induction to Balance each other on 
Circuits. Microfarad*, or Henrys. 

A. C. Crehore. 





1. 


2. 


3. 


4. 


5. 


6. 


7. 


8. 


9. 


10. 


15 


112.58 


56.29 


37.53 


28.15 


22.52 


18.76 


16.08 


14.07 


12.51 


11.258 


20 


63.328 


31.664 


21.109 


15.832 


12.666 


10.555 


9.047 


7.916 


7.036 


6.3328 


25 


40.528 


20.204 


13.509 


10.132 


8.106 


6.755 


5.789 


5.066 


4.503 


4.0528 


33 


23.259 


11.629 


7.419 


5.815 


4.652 


3.877 


3.323 


2.907 


2.584 


2.3259 


40 


15.831 


7.915 


5.277 


3.958 


3.166 


2.638 


2.262 


1.979 


1.759 


1.5831 


60 


7.036 


3.518 


2.345 


1.759 


1.407 


1.173 


1.005 


.889 


.782 


.7036 


80 


3.958 


1.979 


1.319 


.989 


.792 


.659 


.566 


.495 


.439 


.3958 


100 


2.533 


1.266 


.844 


.633 


.507 


.422 


.362 


.316 


.281 


.2533 


130 


1.498 


0.749 


.499 


.375 


.299 


.249 


.214 


.187 


.166 


.1498 





11. 


12. 


13. 


14. 


15. 


16. 


17. 


18. 


19. 


20. 


15 


10.235 


9.38 


8.66 


8.04 


7.505 


7.035 


6.622 


6.255 


5.925 


5.629 


20 


5.757 


5.2775 


4.8714 


4.5235 


4.222 


3.958 


3.7252 


3.518 


3.3330 


3.1664 


25 


3.684 


3.3775 


3.1175 


2.8945 


2.702 


2.533 


2.3840 


2.2515 


2.1330 


2.0264 


33 


2.114 


1.9385 


1.7891 


1.6615 


1.551 


1.4535 


1.3682 


1.292 


1.2242 


1.1629 


40 


1.439 


1.3190 


1.2179 


1.1310 


1.055 


.9895 


.9312 


.S795 


.8332 


.7915 


60 


.639 


.5865 


.5412 


.5025 


.469 


.4445 


.4139 


.3910 


.3703 


.3518 


80 


.359 


.3295 


.3044 


.2S30 


.264 


.2475 


.2328 


.2195 


.2083 


.1979 


100 


.2303 


.2110 


.1948 


.1810 


.169 


.1580 


.1490 


.1405 


.1333 


.1266 


130 


.1362 


.1245 


.1152 


.1070 


.0996 


.0935 


.0812 


.0830 


.0788 


.0749 



Formula : 



LCz 



W> 



(2tt?i) 2 



Where L = coefficient of self induction. 
C= capacity. 
10° = microfarads. 
n = frequency. 



CAPACITY IN MICRO-FARADS. 



113 



CAPACITY I]¥ MICBO-FARADS AID CHARCIXG 
CVRREJVT, PER HIE ©E CIRCUIT, THREE- 

PHASE SYSTEM. 

(Dr. F. A. C. Perrine and Frank G. Baum in Trans. A. I. E. E.) 

Line E.M.F. — 10,000 volts. 60 P.P.S. 



02 








,• to 

2 9 


w 








t* ~ 


<*3 


2* 


<D A 
§ | 


>> 


o 3 

MS 

3^ 


<9 


u 


§ -s 


£ N 


§ 2 






03 rt 


'3 Pr 










os a 




X rt 


s ~ 


a ^ 


o.S 




s s 


•2 rt 


«3 a 




cc 


fl- rt 


O 


Ul 


A~ 


A -rt 


O 'H 


0000 


.46 


12 


.0226 


.0492 


4 


.204 


12 


.01874 


.0408 






18 


.0204 


.0447 






18 


.01726 


.0377 






24 


.01922 


.0418 






24 


.01636 


.0356 






48 


.01474 


.0364 






48 


.01452 


.0317 


000 


.41 


12 


.0218 


.0474 


5 


.182 


12 


.01830 


.0399 






18 


.01992 


.0414 






18 


.01690 


.0368 






24 


.01876 


.0408 






24 


.01602 


.0349 






48 


.01638 


.0356 






48 


.01426 


.0311 


00 


.365 


12 


.0214 


.0465 


6 


.162 


12 


.01788 


.0389 






18 


.01946 


.0423 






18 


.01654 


.0360 






24 


.01832 


.0399 






24 


.01560 


.0342 






48 


.01604 


.0349 






48 


.0140 


.0305 





.325 


12 


.02078 


.0453 


7 


.144 


12 


.01746 


.0389 






18 


.01898 


.0413 






18 


.01618 


.0352 






24 


.01642 


.0379 






24 


.01538 


.0335 






48 


.01570 


.0342 






48 


.01374 


.0290 


1 


.289 


12 


.02022 


.0440 


8 


.128 


12 


.01708 


.0372 






18 


.01952 


.0403 






18 


.01586 


.0341 






24 


.01748 


.0380 






24 


.01508 


.0328 






48 


.0154 


.0337 






48 


.01350 


.0294 


2 


.258 


12 


.01972 


.0372 


9 


.114 


12 


.01660 


.0364 






18 


.01818 


.0305 






18 


.01552 


.0337 






24 


.01710 


.0372 






24 


.01478 


.0317 






48 


.01510 


.0328 






48 


.01326 


.0289 


3 


.229 


12 


.01938 


.0421 


10 


.102 


12 


.01636 


.0356 






18 


.01766 


.0385 






18 


.01522 


.0329 






24 


.01672 


.0364 






24 


.01452 


.0310 






48 


.01480 


.0322 






48 


.01304 


.0284 



Basis of Table. 

1 

C = 



in electro-static units per cm. of circuit. 

c __0 I 0776x£ 



2 log w (£)' 

in micro-farads between one wire and neutral point for L miles of circuit. 

™ . . . E X C X 2 77 X / 

Charging current per wire = T _ — 

V3 x 10 G 
d = distance between wires (inch). E = E.M.F. between Avires. 
r = radius of wire (inch). /= cycles per second. 

L =. length of circuit in miles. C = capacity in M.F. between one wire 

and neutral point. 
2 
Charging current three-phase = — — (= 15.5%) x charging current single- 
V3 
phase for same d, r, L, and E. 



114 



CONDUCTORS. 



CHARGING CURRENT PER HUE OE CIRCUIT. 

Two Parallel Wires. 
Line E.M.F.= 10,000 Volts; Frequency=60 P.P.S; Sine Wave Assumed. 

Stanley Electric Manufacturing Co., Pittsfield, Mass. 





g £ 2 


Charging 

Current 

in 

Amperes. 








2 rn m 

PS fl <o 

"SO 2 


Charging 

Current 

in 

Amperes. 








12 


.0426 








12 


.0353 






0000 


18 
24 
48 
12 


.0385 
.0362 
.0315 
.0411 






4 


18 
24 
48 
12 


.0326 
.0308 
.0274 

.0345 






000 


18 
24 

48 
12 


.0375 
.0353 
.0308 
.0403 






5 


18 
24 

48 

1 

12 


.0319 
.0302 
.0269 

.0337 






00 


18 
24 
48 
12 


.03G6 
.0345 
.0302 
.0392 






6 


18 
24 

48 
12 


.0312 
.0296 
.0264 
.0329 









18 
24 
48 
12 


.0358 
.0328 
.0296 
.0381 








IS 
24 
48 
12 


.0305 
.0290 
.0259 

.0322 






1 


18 


.0349 






8 


18 


.0295 








24 


.0329 






24 


.0284 








48 


.02905 






48 


.02545 








12 


.0372 


| 




12 


.0315 






2 


18 
24 
48 


.0342 
.0322 
.0284 


1 
1 


9 


18 
24 

j 48 


.02925 

.0278 

.0250 








12 


.0365 








12 


.0308 








18 
24 

48 


.0333 
.0315 
.0279 






10 


18 
24 

48 


.0285 
.0273 
.0246 







Charging currents = 



2wNkE 
10« 



E — LineE.M.P. 

A r = Frequency. 

k= Capacity per mile of line in M.F. 



CHARGING CURRENT PER MILE OF CIRCUIT. 115 



o CD 

I? 



a . 
$0* 



ad 
<<os 

coin 1 






iOIOHCO*' 



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iHHHNwco 



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as to t- -* t- 



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)Hiqqi> 

ICNCN COCO 



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& ^3 a 


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ir 


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tioj 


^5 


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^^ 


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ri^d 


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116 



CONDUCTORS. 



ini s i;DA\(E A\ l» REACTANCE OF ALTERNAT- 
ING CURRENT CIRCUITS. 



Let 



Then: 



By Steinmetz. 

R = resistance in ohms. 
Z = impedance. 
E = power E.M.F. 

e = impressed E.M.F. 

tu = 2 it n. 

L = coefficient of self-induction. 

I recurrent. 

c = capacity. 

In circuits containing Resistance and Inductance, 



and 

or diagrammatic ally, 



Impedance, Z, rr VR 2 + L 2 a, 2 , 

e=rVE 2 + PL 2 u> 2 : 





Fig. 8. Fig. 9. 

Circuits containing Resistance and Capacity. 



Impedance, Z,= VR 2 -| — . 



and e = Ve 2 -4- -- 

-^ I r 2 ,„2 



or diagramatically, 





Fig. 10. Fig. 11. 

Circuits containing Resistance, Inductance, and Capacity. 

Impedance, Z, = Vr 2 -f ( L» — ^M • 

and^= Ve 2 + I 2 (lo>-^J 2 . 
or diagramatically, 





TABLE OF INDUCTANCE AND IMPEDANCE. 



117 



TABLE OF iari»lJCTA]¥CJE A]ff» IMPEDANCE. 

Per, Mile of Wire. 
Stanley Electric Manufacturing Co., Pittsfield, Mass. 



dJ* 






*i& 




Inductance. 






Impedance. 




Nd* 


gS 


C 


§31 






^CQ 


N 


N 


N 


N 


N 


N 


N 


N 


N 


N 


N 


N 


8 


~fi 


133 
.944 


125 

~887 


66.6 
.473 


60 
.426 


40 

.284 


25 
.177 


133 
.981 


125 
.926 


m.6 


60 
.502 


40 


25 





.00113 


.542 


.389 


.319 






v> 


.00135 


1.13 


1.06 


.565 


.509 


.339 


.212 


1.161 


1.093 


.624 


.574 


.431 


.340 


oooo 


.'2656 


l.s 


.00148 


1.24 


1.16 


.619 


.558 


.372 


.232 


1.268 


1.190 


.674 


.618 


.457 


.353 






24 


.00156 


1.30 
.969 


1.22 
.911 


.652 
.485 


.588 
.437 


.392 
.291 


.245 

7l82 


1.327 
1.025 


1.249 
.971 


.704 
"7589 


.645 
.551 


.474 
.444 


.361 




.00116 


.381 






1° 


.00139 


1.16 


1.09 


.581 


.524 


.349 


.218 


1.207 


1.140 


.671 


.622 


.484 


.400 


oou 


.3348 


18 


.00152 


1.27 


1.19 


.636 


.573 


.382 


.239 


1.313 


1.236 


.719 


.664 


.508 


.411 






24 
fi 


.00161 


1.34 
1.01 


1.26 
~950 


.673 
.506 


.607 
.456 


.404 
.304 


.253 
.190 


1.381 
1.095 


1.304 
1.040 


.752 
.659 


.693 
.622 


.525 
.520 


.420 




.00121 


.463 






1'" 


.00143 


1.19 


1.12 


.598 


.539 


.359 


.225 


1.263 


1.197 


.732 


.685 


.554 


.479 


00 


.4224 


18 


.00156 


1.30 


1.22 


.652 


.588 


.392 


.245 


1.367 


1.291 


.777 


.724 


.576 


.488 






24 


.00165 


1.38 


1.30 


.690 


.622 


.414 

73IT 


.259 
.195 


1.443 
1.169 


1.367 


.809 
.744 


.752 
.709 


.591 
.617 


.495 




.00124 


1.04 


.973 


.519 


.467 


1.109 


.567 





.5328 


V. 


.00147 


1.23 


1.15 


.615 


.554 


.369 


.231 


1.340 


1.267 


.814 


.769 


.648 


.581 


18 


.00160 


1.34 


1.26 


.669 


.603 


.402 


.251 


1.442 


1.368 


.855 


.805 


.667 


.589 






24 

6 


.00169 


1.41 
1.07 


1.33 
1.00 


.707 
.535 


.637 
.482 


.425 
7322 


.265 
.201 


1.507 
T7263 


1.433 
1.204 


.885 
.858 


.830 
.826 


.682 
.744 


.595 




.00128 


.700 


1 


.6706 


19 


.00150 


1 .25 


1.18 


.627 


.565 


.377 


.236 


1.419 


1.357 


.918 


.877 


.770 


,711 


18 


.00163 


1.36 


1.28 


.682 


.614 


.409 


.256 


1.516 


1.445 


.956 


.909 


.785 


.718 






24 

T 


.00172 


1.44 
1.09 


1.35 
1.02 


.719 
.544 


.648 
.490 


.432 
.327 


.270 
.204 


1.580 
L~379 


1.507 


.983 


.933 


.798 
.906 


.723 




.00130 


1.324 


1.005i .977 


.869 


2 


.8448 


i', 


.00154 


1.29 


1.21 


.644 


.580 


.387 


.242 


1.542 


1.476 


1.062 1.025 


.929 


.879 


if 


.00166 


1.39 


1.30 


.694 


.625 


.417 


.261 


1.627 


1.550 


1.093 1.051 


.942 


.884 







24 

fi 


.00176 


1.47 


1.38 


.736 


.663 


.442 


.276 


1.695 
T547 


1.618 
1.497 


1.1201.074 
1. 205 T. 180 


.953 
T7T19 


.889 




.00134 


1.12 


1.05 


.560 


.505 


.337 


.210 


1.087 


3 


1.067 


12 


.00158 


1.32 


1.24 


.661 


.595 


.397 


.248 


1.697 


1.636 


1.255 


1.222 


1.138 


1.095 


1<s 


.00170 


1.42 


1.33 


.711 


.641 


.427 


.267 


1.776 


1.705 


1.282 


1.245 


1.149 


1.100 







24 
fi 


.00179 


1.50 
1.15 


1.41 
1.08 


.749 

.577 


.674 
.520 


.450 
7347 


.281 
.217 


1.841 
1.770 


1.768 
T.726 


1.304 
1.464 


1.262 
1.443 


1.158 
^.390 


1.103 




.00138 


1.363 


4 


1.346 


12 


.00162 


1.35 


1.27 


.678 


.610 


.407 


.254 


1.906 


1.851 


1.507 


1.478 


1.406 


1 .370 


18 


.00173 


1.44 


1.36 


.724 


.652 


.435 


.272 


1.971 


1.913 


1.528 


1.496 


1.415 


1.373 






24 


.00182 


1.52 


1.43 


.761 


.686 


.457 


.286 


2.030 


1.964 


1.546 


1.511 


1.421 


1.376 






6 


.00141 


1.18 


1.11 


.590 


.531 354 


.221 


2.069 


2.030 


1.799 


1.781 


1 .736 


1.714 


5 


1.700 


12 


.00165 


1.38 


1.30 


.690 


.622 


.414 


.259 


2.190 


2.140 


1.835 


1.810 


1.750 


1.720 


18 


.00177 


1.48 


1.39 


.740 


.667 


.445 


.278 


2.254 


2.196 


1.854 


1.826 


1.757 


1.723 






24 
7) 


.00187 


1.56 
1.2T 


1.47 
1.14 


.782 
.606 


.705 
.546 


.470 
.364 


.294 

.228 


2.307 
2^457 


2.247 
2.423 


1.871 


1.840 

2.207 


1.764 
2.169 


1.725 




.00145 


2.222 


2.150 


6 


2.138 


12 


.00168 


1.40 


1.32 


.703 


.633 


.422 


.264 


2.556 


2.513 


2.251 


2.230 


2.179 


2.154 


18 


.00181 


1.51 


1.42 


.757 


.682 


.455 


.284 


2.618 


2.567 


2.268 


2.244 


2.186 


2.157 






24 
"6 


.00190 


1.59 


1.49 


.795 
.623 


.716 
.561 


.477 
7374 


.298 
.234 


2.664 
2.969 


2.606 ( 2.281 


2.255 


2.191 
2.724 


2.159 




.00149 


1.24 


1.17 


2.941 


2.769 


2.756 


2.708 


7 


2.698 


12 


.00172 


1.44 


1.35 


.719 


.648 


.432 


.270 


3.058 


3.017 


2.792 


2.775 


2.732 


2.711 


18 


.00184 


1.54 


1.44 


.770 


.693 


.462 


.289 


3.107 


3 058 


2.806 


2.786 


2.737 


2.713 






24 
~6 


.00194 


1.62 
L~28 


1.52 
1.20~ 


.811 
.640 


.731 

.577 


.487 
.384 


.305 
.240 


3.147 

37639 


3.097 
37611 


2.817 
3.466 


2.795 
37455 


2.742 

37428 


2.715 




.00153 


3,414 


8 


3.406 


12 


.00175 


1.46 


1.37 


.732 


.659 


.440 


.275 


3.706 


3.671 


3.484 


3.469 


3.434 


3.417 


18 


.00188 


1.57 


1.48 


.786 


.708 


.472 


.295 


3.750 


3.714 


3.495 


3.479 


3.439 


3.419 






24 
6 


.00197 


1.65 


1.55 


.824 
.657 


.742 

.592 


.495 
.394 


.309 
.246 


3.785 
47488 


3.742 
4.466 


3.504 
47343 


3.486 
4.334 


3.442 
4.311 


3.420 




.00157 


1.31 


1.23 


4.300 


9 


4.293 


12 


.00179 


1.50 


1.41 


.749 


.674 


.450 


.281 


4.548 


4.519 


4.358 


4.346 


4.317 


4.302 


18 


.00192 


1.60 


1.51 


.803 


.723 


.482 


.301 


4.581 


4.551 


4.367 


4.354 


4.320 


4.304 






24 


.00201 


1.68 


1.58 


.841 


.757 


.505 


.316 


4.610 


4.575 


4.375 


4.359 
5.451 


4,323 
5.432 


4.305 






6 


.00161 


1.34 


1.26 


.673 


.607 


.404 


.253 


5.580 


5.562 


5.459 


5.423 


10 


5.417 


12 


.00184 


1.54 


1.44 


.770 


.693 


.462 


.289 


5.632 


5.605 


5.471 


5.461 


5.437 


5.425 


18 


.00196 


1.64 


1.54 


.820 


.739 


.492 


.308 


5.660 


5.632 


5.479 


5.467 


5.439 


5.426 




1 


24 


.00205 


1.71 


1.61 


.857 


.772 


.515 


.322 


5.680 


5.651 


5.484 


5.472 


5.441 


5.427 



D" = distance in inches between the wires. N = cycles per second. 



118 



CONDUCTORS. 



Impedance Factors and Multipliers. 

Frequency = 100. 



. <D 


Dist. between 


Dist. between 


Dist. between 


Dist. between 


»3 


centres, 6". 


centres, 12". 


centres, 24". 


centres, 48". 


I 


























Factor. 


Multi- 
plier. 


Factor. 


Multi- 
plier. 


Factor. 


Multi- 
plier. 


Factor. 


Multi- 
plier. 


2" 


30.813 


.094844 


41.263 


.170170 


51.717 


.26737 


62.171 


.386420 


1* 


19.809 


.039142 


25.692 


.065905 


31.574 


.099596 


37.459 


.140223 




10.362 


.010636 


12.919 


.016683 


15.573 


.024151 


18.182 


.032957 




6.4873 


.004108 


7.9445 


.006212 


9.4039 


.008745 


10.869 


.011712 


5 


3.3829 


.001044 


4.0118 


.001509 


4.6474 


.002059 


5.2874 


.002696 


0000 


2.9793 


.000787 


3.5060 


.001129 


4.0400 


.001532 


4.5787 


.001996 


000 


2.5004 


.000525 


2.9078 


.000746 


3.3225 


.001000 


3.7426 


.001301 


00 


2.1227 


.000351 


2.4341 


.000492 


2.7528 


.000658 


3.0794 


.000848 





1.8316 


.000235 


2.0679 


.000328 


2.3130 


.000435 


2.5642 


.000558 


1 


1.6021 


.000157 


1.7778 


.000216 


1.9622 


.000285 


2.1531 


.000363 


2 


1.4306 


.000105 


1.5592 


.000143 


1.6958 


.000187 


1.8386 


.000238 


3 


1.3024 


.000069 


1.3944 


.000094 


1.4935 


.000123 


1.5982 


.000155 


4 


1.2092 


.000046 


1.2737 


.000062 


1.3439 


.000081 


1.4190 


.000101 


5 


1.1428 


.000031 


1.1868 


.000041 


1.2357 


.000053 


1.2884 


.000066 


6 


1.0968 


.000020 


1.1266 


.000027 


1.1598 


.000035 


1.1960 


.000043 


7 


1.0649 


.0000134 


1.0847 


.0000176 


1.1070 


.0000225 


1.1313 


.0000279 


8 


1.0440 


.0000089 


1.0573 


.0000118 


1.0722 


.0000149 


1.0886 


.00001S5 


9 


1.0288 


.0000058 


1.0373 


.0000076 


1.0470 


.0000096 


1.0576 


.00001 IS 


10 


1.0196 


.0000039 


1.0234 


.0000049 


1.0309 


.0000063 


1.0377 


.0000077 



To find factor for any frequency, V(Multiplier X/ 2 )+ 1 = factor required. 

For convenience of the engineer impedance factors for the frequencies 
most generally used have been computed by Prof. Forbes, and follow. To 
find the true drop in line, multiply ohmic drop by factors in tables below. 
Diameters are given in inches and B. & S. gauge. 

Impedance factors. 









<D 


o> 




03 


0> 


o> 


45 


A 6 




15 o 








fl .g 


el .5 ° 


ii| 


3.52 


p ft 


fl^ft 


10 "# § 

fi c, ft 


**2 
fi^ft 


.3 3* 


H ft 


.2=2 § 

p~ft 


■fi M p 

a ft 


■2 22 § 
fi^ft 


Fr 


zquency 


/= 15 






Ft 


•equency 


/=26 




1 


1.842 


2.182 


2.535 


| 2.904 


2 


7.7638 


10.37 


12.912 


15.55 


I 


1.387 


1.546 


1.720 


1.903 


1£ 


5.014 


6.454 


7.831 


9.017 


I 


1.111 


1.157 


1.210 


1.267 


1 


2.7654 


3.3826 


4.012 


4.642 


0000 


1.085 


1.120 


1.167 


1.203 


f 


1.889 


2.209 


2.543 


2.885 


000 


1.057 


1.081 


1.108 


1.137 




1.285 


1.393 


1.513 


1.637 


00 


1.038 


1.054 


1.068 


1.090 















1.0264 


1.036 


1.048 


1.061 


0000 


1.222 


1.3068 


1.3996 


1.498 












000 


1.152 


1.2104 


1.2763 


1.345 




/— 2 







00 


1.1034 


1.1422 


1.1876 


1.235 


1 


2.291 


2.771 


3.261 


3.768 





1.0710 


1.0973 


1.1277 


1.160 


1 


1.624 


1.863 


2.116 


2.378 


1 


1.0478 


1.0676 


1.0853 


1.108 


h 


1.190 


1.263 


1.351 


1.441 


2 


1.0324 


1.0443 


1.0583 


1.071 


0000 


1.146 


1.206 


1.271 


1.341 


3 


1.0216 


1.0293 


1.0384 


1.048 


000 


1.100 


1.139 


1.184 


1.233 


4 


1.0142 


1.0191 


1.0247 


1.031 


00 


1.067 


1.093 


1.123 


1.155 


5 


1.0094 


1.0126 


1.0162 


1.0203 





1.046 


1.063 


1.084 


1.106 


6 


1.0063 


1.0084 


1.0107 


1.0134 



IMPEDANCE AND REACTANCE. 



119 



Impedance factors. — Continued. 





® 


a>. a> 


a> 


I ® 


0> <D 


a> 


* 


« ^ 


» 


« 


« 


*. <j3 w 


» 


« 


° . ." 


eS a P 

ft o 






§.a° 


r-i _: •-> 


gTJ bC 

5 5 2 
Q 3 


ft h 


§«3 
.2 2 § 


Sis 


ISO 
.22 § 


Frequency f = 25 




/=60 










1 


6.2681 


7.8194 


9.3778 


10.938 


7 


1.0042 


1.0055 


1.0070 


1.0087 


! 


3.9738 


4.8334 


5.6995 


6.5698 


8 


1.0027 


1.0035 


1.0045 


1.0056 


2.1817 


2.5365 


2.9009 


3.2718 


9 


1.0018 


1.0023 


1.0029 


1.0036 


0000 


1.9583 


2.2505 


2.5527 


2.8614 


10 


1.0011 


1.0015 


1.0019 


1.0024 


000 


1.7002 


1.9194 


2.1480 


2.3838 








00 


1.5040 


1.6651 


1.8352 


2.0134 











1.3593 


1.4763 


1.6019 


1.7627 




/=33 




/= 80 




1 


3.51 


4.381 


5.221 


6.081 


1 


8.3108 


10.387 


12.474 


14.557 


1 


2.338 


2.781 


3.237 


3.700 


1 


5.2244 


6.3840 


7.5478 


8.7151 


* 


1.462 


1.625 


1.803 


1.982 


i 


2.7720 


3.2649 


3.7339 


4.2722 


0000 


1.362 


1.495 


1.634 


1.780 


0000 


2.4577 


2.8683 


3.2873 


3.7119 


000 


1.252 


1.344 


1.445 


1.551 


000 


2.0884 


2.4024 


2.7249 


3.0536 


00 


1.173 


1.238 


1.311 


1.384 


00 


1.8011 


2.0376 


2.2825 


2.5355 





1.121 


1.165 


1.215 


1.268 





1.5833 


1.7597 


1.9451 


2.1373 




/ = 40 




/=130 




1 


4.2447 


5.2661 


6.2961 


7.3302 


1 


13.44416.832 


20.227 


23.623 


t 


2.7520 


3.3072 


3.8719 


4.4428 


1 


8.3925 10.295 


12.191 


14.104 


* 


1.6342 


1.8480 


2.0726 


2.3050 


h 


4.3185J 5.1487 


5.9842 


6.8233 


0000 


1.5033 


1.6753 


1.8579 


2.0480 


0000 


3.7828 ! 4.4814 


5.1860 


5.8942 


000 


1.3566 


1.4808 


1.6136 


1.7553 


000 


3.1426 3.6878 


4.2387 


4.7939 


00 


1.2493 


1.3371 


1.4326 


1.5354 


00 


2.6316' 3.0529 


3.4808 


3.9161 





1.1747 


1.2345 


1.3023 


1.3756 





2.2328 


1 2.5567 


2.8898 


3.2283 



To find true drop in line, multiply ohmic drop by factors in these tables. 
* Diameter in inches, Gauge Brown & Sharp. 

Impedance ^Determinations for Three-phase Circuits. — 

In theory the phases of a three-phase circuit differ 120°, although seldom 
exactly so in practice. This phase difference affects each wire as if it had 
one return wire in place of two ; and in calculating the inductive effects, 
each wire must be treated as if it had a return wire in the position of one of 
the other two, that is, the three wires may be treated as if each was a sepa- 
rate circuit having no return wire. 

Two- or Q,uarter-phase Circuits. — As used at Niagara, the two 
phases are separate, and all inductive determinations can be made as if for 
two separate and adjacent circuits. 

Mutual Induction of Circuits. — When two alternating-current 
circuits are carried close together, and especially if the adjacent wires of 
the two circuits lie near together as compared to the two wires of the cir- 
cuit, there is apt to be an interference or mutual induction of one current 
or the other, unless measures are taken to prevent it. It is caused by the 
linking together of lines of force from the two circuits, and must be com- 
pensated for by so arranging the relative positions of the circuits that at 
some other point on the line an equal number of lines will be interlinked in 
the opposite direction, and thus neutralize each other. 

"When alternating circuits were first erected, it was customary to place all 
the right-hand wires of the circuit on one side of a pole, and all the left-hand 
wires on the other ; and most commonly the two outside wires were of one 
circuit, the next two inside the next circuit, and so on. 

In many places where this method was used, and the distances great and 
the current high, it was soon found that incandescent lamps fluctuated in a 
regular periodic manner, which was first laid to engine fly-wheels and too 
heavily loaded engines. Of course, this was soon found to be an error, the 
fault discovered, and the conductors rearranged. 



120 



CONDUCTORS. 



The effect is caused by one circuit acting as a secondary to the other ; and 
if the cycles are similar, the mutual induction will tend to increase the 
drop in one circuit and diminish it in the other. If, however, the cycles are 
not alike, the potential will rise and fall periodically when the maximum 
values coincide, or the tops of the waves come into step at the same 
moment. Both conditions are annoying, and under certain particular 
arrangements are capable of producing damaging results. 

Mutual induction, or rather its evil effects, can be overcome by arranging 
the conductors in such relative positions as to make the flux from one part 
of a circuit counteract that in another part, as shown in the following 
diagrams. 

If lines are not very long, and potentials not too high, so as to induce bad 
effects from static capacity, it will be sufficient to place both wires of a cir- 
cuit near together as compared with the distance between adjacent circuits, 

Arrang-ement of lines for no J?I urual Induction. 

s\ A 

13 3 3| 2 2 2 2| 
2 2 4 4 

KM 



Fig. 14. 

The above change should be made so as to cover the entire distance, each 
location of circuit being for one-quarter of the entire length. 

Niagara Line. — The conductors on this line are bare cables of 19 
strands, equivalent to 350,000 circuit mils, and are arranged as shown in 
the following diagram. The first arrangement was with two three-wire cir- 





->|< — 1-1 



± 



A 



\ 



Fig. 15. Niagara-Buffalo Line. 11000 to 22000 Volts. 

cuits on the upper cross-arm, the wires being 18 inches apart. So much 
trouble was experienced from short circuits by wires and other material 
being thrown across the conductors, that the middle wire was lowered to 
the bottom cross-arm as shown, since which time no trouble has been 
experienced. With porcelain insulators tested to 40,000 volts there is no 
appreciable leakage. These circuits are interchanged at a number of 
points to avoid inductive effects. 



IMPEDANCE AND REACTANCE. 



121 



Three-phase Circuits.— The diagram (Fig. 16) shows the favorite 
arrangement of one of the larger companies as it makes lines conveniently 
accessible for repairs. Under the ordinary loads usual in the smaller 
plants the unbalancing effect is so small as to be inappreciable. 




Fig. 16. Convenient Arrangement of Three-phase Lines for 6000-10000 Yolts. 

Balanced Line, Three-I*hase. — The following diagram shows 
an arrangement of the conductors of a three-phase circuit, which will be 
balanced in all its effects if there be but one circuit. The distances, 18 
inches apart, are about standard for pressures as high as 12,000- volts. 




Fig. 17. Balanced Arrangement for Three-phase Lines. 



This arrangement is perhaps not so convenient for repairs, but is symmet- 
rical in all respects. 

If there be more than one circuit of this balanced arrangement, and the 
difference of phase is enough so that interference is found, then one or 
more of the circuits will have to be changed as shown in the following 



122 



CONDUCTORS. 



diagram (Fig. 18), the principle being to bring each of the three wires 
ot a circuit into the same relation with other circuits for an equal length 
or distance. 






Fig. 18. Arrangement of Three Three-phase Circuits, each Equilaterally 
Placed. In this Arrangement there is no Effect from One Circuit on 
Another. 



_T8- ^ 1 8- i-J[ 



Fig. 19. 



Three-phase Circuit in Same Plane. — It is sometimes advan- 
tageous to place all the conductors on one cross-arm on the same level as 
in the preceding diagram. In this case, if the load is heavy enough to 
cause interference between conductors, then two interchanges of Avires 
should be made, dividing the circuit into three equal parts as shown. This 
will bring every wire into similar relations with all others, and the interfer- 
ence will therefore be the same on all. In order that this balancing effect 
should be.correct along a line having branches, the reversals should be 
made between all branches; for instance, between the dynamo and the 
first branch there should be two reversals as shown, and between the first 
and second branches the reversals should be repeated, and so on. 



IMPEDANCE AND REACTANCE. 



123 



If Wires of Three-phase Circuit are on same Plane, then they should be 
interchanged twice between Points when Branches are attached, as in 
Fig. 20. 



Fig. 20. 



p — 18 — >| 



L, 



Fig. 21. Another Arrangement of Two-phase Circuit. No Reversal of 
Phases necessary. 

Two-phase Four-wire Circuits. — The arrangement of conduc- 
tors shown in Fig. 21 is probably the best for two-phase work, as no 



PHASE A. 
-1 8" j4* 1 




PHASE B. 
1 8- >ft 1 : 



Fig. 22. 



124 



CONDUCTORS. 



reversals of wires are needed, the inductive effects of the wires of one 
circuit on those of the other are neutralized. 

Two-Phase Circuits in Same Plane. — If the phases are treated 
as separate circuits, and carried well apart, the interference is trifling ; and 
should the loads carried be heavy enough to cause noticeable effect, the re- 
versal of one of the phases in the middle of its length will obviate it. Tho 
following diagram illustrates the meaning. 



phas e b. y r 



Fig. 23. Arrangement of Two-phase Four-wire Circuit with Wires on 
same Plane. Wires of One Phase should be interchanged at the Middle 
Point of the Distance between Branches, and between its Origin and 
First Branch. 

Messrs. Scott and Mershon of the Westinghouse Electric and Manufactur- 
ing Co. have made special studies of the question of mutual induction of 
circuits, both in theory and practice ; and their papers can be found in the 
files of the technical journals, and supply full detail information. 

Capacity and Inductance. — In order to completely neutralize 
phase displacement due to distributed inductance a distributed capacity is 
essential. Localized capacity can, however, produce a partial neutraliza- 
tion. Excessive distributed capacity can also be partially neutralized by 
inserting inductances at proper intervals. In treating of local neutraliza- 
tion of capacity by inductance, the assumption is frequently made that the 
capacity is constant irrespective of the voltage, and that the inductance is 
constant irrespective of the current. Under these conditions neutralization 
can be obtained. As, however, inductance is dependent upon the perme- 
ability of the associated magnetic circuit, and permeability varies with the 
saturation of the iron, — that is with the current, — complete neutralization 
cannot be obtained with iron inductances. 

Over-excited synchronous motors, or synchronous converters, take cur- 
rents which lead the electromotive force impressed upon them, and they 
therefore operate as condensers, and they may be utilized advantageously 
in neutralizing the line inductance. The power factor of the transmission 
system can therefore be varied by varying their excitation. 

ALIER^ATIllft WIRING AHHtt COjJUVKCTIOltfS. 

By General Electric Company. 
General Wiring- Formulas 

The following general formulae may be used to determine the size of con- 
ductors, volts lost in the line, and current per conductor for any system of 
electrical distribution. 

D X W 
Area of conductor, Circular Mils rr — — x K • 

P X E 

Volts loss in line = X M. 

W 

Current in main conductors = -=- X T. 

IL 

Dz=z Distance of transmission (one way), in feet. 
W = Total watts delivered to consumer. 
P = Per cent loss in line of W. 

E=z Voltage between main conductors at receiving or consumers' end 
of circuit. 



ALTERNATING WIRING AND CONNECTIONS, 



125 





o 

m 

<V 


Values of K. 


Values of T. 


System. 


Per cent power factor. 


Per cent power factor. 




100 


95 


90 


85 


80 


100 


95 


90 


85 


80 


Single-phase .... 
Two-phase (four-wire) 
Three-phase (three-wire) 


6.04 
12.08 
9.06 


2160 
1080 
1080 


2400 
1200 
1200 


2660 
1330 
1330 


3000 
1500 
1500 


3380 
1690 
1690 


1.00 
.50 

.58 


1.05 
.53 

.61 


1.11 

.55 
.64 


1.17 
.59 
.68 


1.25 
.62 
.72 



The value of K for any particular power factor is obtained by dividing 
2160, the value for continuous current, by the square of that power factor 
for single-phase, and by twice the square of that power factor for three- 
wire three-phase, or four-wire two-phase. 

The value of M depends on the size of wire, frequency and power factor. 
It is equal to 1 for continuous current, and for alternating current with 100 
per cent power factor and sizes of wire given in the following table of 
wiring constants. 

The figures given are for wires 18 inches apart, and are sufficiently accu- 
rate for all practical purposes, provided the displacement in phase between 
current and E.M.F. at the receiving end is not very much greater than that 
at the generator ; in other words, provided that the reactance of the line is 
not excessive, or the line loss unusually high. For example, the constants 
should not be applied at 125 cycles if the largest conductors are used, and 
the loss 20 % or more of the power delivered. At lower frequencies, how- 
ever, the constants are reasonably correct, even under such extreme con- 
ditions. They represent about the true values at 10 % line loss, are close 
enough at all losses less than 10 %, and often, at least for frequencies up to 
40 cycles, close enough for even much larger losses. Where the conductors 
of a circuit are nearer each other than 18", the volts loss will be less than 
given by the formulae, and if close together, as with multiple conductor 
cable, the loss will be only that due to resistance. 

The value of T depends on the system and power factor. It is equal to 1 
for continuous current, and for single-phase current of 100 per cent power 
factor. 

The value of A and the weights of the wires in the table are based on 
.00000302 lb. as the weight of a foot of copper wire of one circular mil area. 

In using the above formulae and constants, it should be particularly 
observed that P stands for the per cent loss in the line of the delivered 
power, not for the percent loss in the line of the power at the generator ; 
and that E is the potential at the end of the line and not at the generator. 

When the power factor cannot be more accurately determined, it may be 
assumed to be as follows for any alternating system operating under aver- 
age conditions : Lighting with no motors, 95% ; lighting and motors to- 
gether, 85 % ; motors alone, 80 %. 

In continuous current three-wire systems, the neutral wire for feeders 
should be made of one-third the section obtained by the formulae for either 
of the outside wires. In both continuous and alternating current systems, 
the neutral conductor for secondary mains and house-wiring should be 
taken as large as the other conductors. 

When both motors and lights are used on the Monocyclic System, the pri- 
mary circuit should be figured as if all the power was transmitted over the 
outside wires, and the size of the power wire should be in the proportion to 
either outside wire as the motor load in amperes is to the total load in am- 
peres. Secondary wires leading directly to induction motors on the Mono- 
cyclic system should all be of the same size as for a single-phase circuit of 
the same kilowatt capacity and power factor. The three wires of a three- 
phase circuit, and the four wires of a two-phase circuit should all be made 
the same size, and each conductor should be of the cross section given by 
the first formula. 



126 



CONDUCTORS. 





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INDUCTION MOTORS. 



127 



GENERATORS. 

The generators are rated by their volt-ampere capacity and their apparent 
watts, and not their actual watts, so that the size has to be increased if the 
power-factor of the system is low. 

TRAXS-FORTTERS. 

For lighting circuits using small transformers, the voltage at the prima- 
ries of the step-down transformers should be made about 3% higher than the 
secondary voltage multiplied by the ratio of transformation, to allow for the 
drop in transformers. In large lighting transformers this drop may be as low- 
as 2%. Standard lighting transformers have a ratio of 10 to 1 or some mul- 
tiple thereof. 

For motor circuits, the voltage at the primaries of step-down transformers 
should be made about 5% higher than the secondary voltage multiplied by 
the ratio of transformation. Transformers used with 110 volt motors on any 
60-cycle system should have a ratio of 4§ to 1, 9 to 1, or 18 to 1 respectively 
for 1040, 2080, and 3120 volt generators. Transformers with a ratio of 10 or 
20 to 1 should on no account be installed with motors operated from Mono- 
cyclic generators of standard voltage. The transformer capacity in kilowatts 
should be the same as the motor rating in horse-power for medium-sized 
motors, and slightly larger for small motors, and where only two trans- 
formers are used. 

Capacities of Transformers to l»e used with ©©-Cycle 
Induction Motors. 



Size of Motor. 


Kilowatts per Transformer. 


Horse-Power. 


Two Transformers. 


Three Transformers. 


1 


.6 


.6 


2 


1.5 


1 


3 


2 


1.5 


5 


3 


2 


7* 


4 


3 


10 


5 


4 


15 


7.5 


5 


20 


10 


7.5 


30 


15 


10 


50 


25 


15 


75 




25 



ODIJCTIOTir MOTORS. 

The standard (General Electric) induction motors for three-phase and for 
monocyclic circuits are wound for 110 volts, 220 volts, and 550 volts ; motors 
of 50 H. P. and above are, in addition, wound for 1040 volts and 2080 volts. 
Motors for the two latter voltages are hot built in sizes of less than 50 H. P. 
Where the four-wire three-phase distribution system is used, motors can 
also be wound for 200 volts. 

The output of an induction motor varies with the square of the voltage at 
the motor terminals. Thus, if the volts at the terminals happen to be 15% 
low, that is, only 85% of the rated voltage, a motor, which at the rated volt- 
age gives a maximum of 150% of its rated output, will be able to give at the 
15% lower voltage, only ( T 8 o 5 o) 2 X 150 = 108 % of its rated output, and at full 
load will have no margin left to carry over sudden fluctuations of load while 
running. 



128 



CONDUCTORS. 



Thus it is of the utmost importance to take care that the volts at the motor 
terminals are not below the rated volts, hut rather slightly above at no load, 
so as not to drop below rated voltage at full-load or over-load. 

The output of the motor may be increased by raising the potential ; in 
this case, however, the current taken is increased, especially at light loads. 

The direction of rotation of an induction motor on a three-phase or mono- 
cyclic circuit, can be reversed by changing any two of the leads to the field. 

Like all electrical apparatus, the induction motor works most efficiently 
at or near full load, and its efficiency decreases at light load. Besides this, 
when running at light load, or no load, the induction motor draws from the 
lines a current of about 30% to 35% of the full-load current. This current 
does not represent energy, and is not therefore measured by the recording 
watt-meter ; it constitutes no waste of power, being merely what is called an 
idle or" wattless" current. If, however, many induction motors are ope- 
rated at light loads from a generator, the combined wattless currents of the 
motors may represent a considerable part of the rated current of the gene- 
rator, and thus the generator will send a considerable current over the line. 
This current is wattless, and does not do any work, so that in an extreme 
case an alternator may run at apparently half -load or nearly full-load cur- 
rent, and still the engine driving it run light. While these idle currents are 
in general not objectionable, since they do not represent any waste of 
power, they are undesirable when excessive, by increasing the current-heat- 
ing of the generator. Therefore it is desirable to keep the idle currents in 
the system as low as possible, by carefully choosing proper capacities of 
motors. These idle currents are a comparatively small per cent of the total 
current at or near full-load of the motor, but a larger per cent at light loads. 
Therefore care should be taken not to install larger motors than necessary 
to do the required work, since in this case the motors would have to work 
continuously at light loads, thereby producing a larger per cent of idle cur- 
rent in the system than would be produced by motors of proper capacity ; 
that is, motors running mostly between half-load and full-load. 



Current taken by General Electric Co. Three-phase In- 
duction motors at HO Volts. 









Starting 


Starting 


H. P. of Motor. 


Full-Load 


Current at 


Current 


Current. 


150% of Full- 


at Full-Load 








Load Torque. 


Torque. 




1 


6.3 


19 






2 


12 


36 






3 


18 


54 






5 


28 


*42-84 


28 




10 


54 


70 


54 




15 


81 


120 


81 




20 


112 


167 


112 




30 


168 


252 


168 




50 


268 


400 


268 




75 


390 


585 


390 




100 


550 


825 


550 




150 


780 


1180 


780 



* The 5 H. P. motor is made with or without starting-switch. 



The current taken by motors of higher voltage than 110 will be proportion- 
ally less. The above are average current values, and in particular cases the 
values may vary slightly. 






CONNECTIONS. 



coarMECxioars. 



129 



Isolated motors running on the Monocyclic System are operated from two 
transformers, connected as shown in Fig. 24. Where there is no high-tension 
transmission line, the step-up and step-down transformers are not required, 
and only the two motor transformers shown at the right in the diagram are 
used. 

The connections of a Monocyclic circuit for the operation of a three-wire 





Fig. 24. 



Fig. 25. 



secondary lighting system and motors is shown in Fig. 25. The main trans- 
former has three terminals brought out from each winding, and a supple- 
mentary motor transformer is used and connected as shown. 

Where this connection is used for the operation of a single motor, the kilo- 
watt rating of the supplementary transformer should be about one-half of 
the motor rating in horse-power. This arrangement is primarily intended 
for secondary mains carrying lights and a number of motors. Judgment 
should be exercised in the use of this arrangement, since, if the motors con- 
nected are large as compared with the total capacity of the transformers, 
the fluctuations of load may effect the lights to an objectionable degree 
through variations of drop in the transformers. The motor load being in- 
ductive, it will cause wider variations of voltage in the transformers than 
would be experienced with the same current delivered to lights. 

The connections of three transformers, with their primaries, to the genera- 
tor and their secondaries to the induction motor, in a three-phase system, 
are shown in Fig. 26. The three transformers are connected with their pri- 
maries between the three lines leading from the generator, and the three 
secondaries are connected to the three lines leading to the motor, in what is 
called delta connection. 

The connection of two transformers for the supply of an induction motor 
from a three-phase generator is shown in Fig. 27. It is identical with the 




Fig. 26. 



Fig. 27. 



arrangement in Fig. 26, except that one of the transformers is left out, and 
the two other transformers are made correspondingly larger. The copper 
required in any three-wire, three-phase circuit for a given power and loss is 
75%, as compared with the two-wire single-phase, or four-wire two-phase 
system having the same voltage between lines. 

The connections of three transformers for a low-tension distribution sys- 
tem by the four-wire three-phase system are shown in Fig. 28. The three 



t, 


JiqJW. 


1_ 


T I fado.v. 


i 


HsV. 


Pf 



in 



Fig. 28. 



Fig. 29. 



transformers have their primaries joined in delta connection, and their sec- 
ondaries in " Y " connection. The three upper lines are the three main 
three-phase lines, and the lowest line is the common neutral. The difference 



130 CONDUCTORS, 

of potential between the main conductor is 200 volts, while that between 
either of them and the neutral is 115 volts. 200 volt-motors ai - e joined to the 
mains, while 115 volt-lamps are connected between the mains and the neutral. 
The neutral is similar to the neutral wire in the Edison three-wire system, 
and only carries current when the lamp load is unbalanced. 

The potential between the main conductors should be used in theformuhe, 
and the section of neutral wire should be made in the proportion to each of 
the main conductors that the lighting load is to the total load. When lights 
only are used, the neutral should be of the same size as either of the three 
main conductors. The copper then required in a four-wire three-phase sys- 
tem of secondary distribution to transmit a given power at a given loss is 
about 33.3%, as compared with a two-wire single-phase system, or a four-wire 
two-phase system having the same voltage across the lamps. 

The connections of two transformers for supplying motors on the four-wire 
two-phase system are shown in Fig. 29. This system practically consists of 
two separate single-phase circuits, half the power being transmitted over 
each circuit when the load is balanced. The copper required, as compared 
with the three-phase system to transmit given power with given loss at the 
same voltage between lines, is 133J % — that is, the same as with a single- 
phase system. 



APPLICATIOHf§ OF GENERAL WIRING 

jFOitifiui^:. 

Contitfuous Current. 

TWO-WIRE SYSTEM. 

Example : 500 half ampere, 110 volt-lamps. Distance to lights, 1000 ft.; 
loss in line = 10% of delivered power. 

M = 2160 X 1000^(5 00 X -5X110) = m ^ Q M 
Volts drop to lamp = 10X ^ Xl — U volts. 

THREE-WIRE SYSTEM. 

Example : 600 half -ampere, 110 volt-lamps. Distance to distribution point, 
1500 ft. Volts between outside lines at distributing point. 220. Loss in line 
= 8% of delivered power. 

Area of outside conductors = 

2160 x 1500 xteoox -5x110) = 276100 c M 

The area of the neutral feeder is 276,100 x h = 92,030 CM. 

8 X 220 X 1 
Volts drop in circuit = — - — = 17.6. 

220 + 17.6=; 237.6 volts at station between outside lines; and 118.8 volts 
between outside wires and neutral. 

Alternating- Currents. 

TWO-WIRE SIXGLE-PHASE SYSTEM. 125 CYCLES. 

Example : 1000, 16 c.p., 3.6 watt, 104 volt-lamps. 10 to 1 transfprmers 
Distance, 2000 ft. to generator. 2 volts less in secondary wiring. Drop in 
transformers for lighting is 3%. Loss in primary line to be equal to about 
5% of power delivered at transformers. Efficiency of transformers. 97%. 

Volts at transformer primaries = 106 X 10 X 1.03= 1091.8. 1000 X 16 X 3.6 = 

57,600 watts. -^ — 5== about 60,600 watts at transformer primaries. 



APPLICATIONS OF GENERAL WIRING FORMULA. 131 

No. 3 B. and S. = 52,633 CM. 
2000x60,600x2400 . _,„ . __-. . 

j — 52 633 x 1091 8 2 =4 - 64% loss of delivered power, in primary wiring. 
Volts loss in primary lines = 

4.64 X 1091.8 X 1.35 CQ . 

■ ioo = 68 - 4 - 

1091.8 + 68.4 = 1160.2 volts at generator. 

TWO-WIRE SYSTEM. 60 CYCLES. 

Example : The same load and losses as for the previous problem. 
Volts at transformor primaries = 106 x 10 x 1.03 = 1091.8. 
Load at transformer primaries — 60,600 watts. 
No. 3 B. and S. wire gives 4.64% loss in primary wiring. 
Volts loss in primary lines = 

4.64 X 1091.8 X 1.14 __ _ 

ioo = W " 7 ' 

1091.8 + 57.7 = 1149.5 volts at generator. 

TWO-WIRE SYSTEM, WITH THREE-WIRE SECONDARIES. 60 OR 125 CYCLES. 

The primary wiring is identical with that for the two-wire system. The 
secondary wiring is calculated, using the voltage between outside lines, and 
the three wires are made of the same cross-section. The drop in voltage on 
the secondary wiring as obtained by the formula is the drop between outside 
lines, and is twice the drop to each individual lamp. 

Monocyclic System. OO Cycles. 

MOTOR AND LIGHTS ON SEPARATE TRANSFORMERS. (See Fig. 25.) 

Example: 1500 half-ampere, 104 volt-lamps. One 25 H.P. 110 volt-induc- 
tion motor ; efficiency, 85%. Distance from generator to transformers, 
3000 ft. Distance from transformers to motor, 100 ft. Loss in motor circuit, 
1\%. Loss of energy in transformers, 3%. Loss in primary circuit, 4%. 
Generator voltage, 1040 at no load. 

25 X 746 
Input at motor = — — = 21,940 watts. 

CM.=?^? X 3380 = 245,000. No. 0000 B. and S. wire = 211,600 
2.5 X lHr 

1 49 
CM.; but as two No. B. and S. will give the same loss, and 7^= 71.3% as 

great a drop in voltage, they are preferable. Making each motor lead of two 

,. . ', „ 100 X 21,940 X 3380 „ nnl 

No. B. and S. wires in parallel, then, P = 105 599 x 2 x HO 2 = 

t- 1* 1 * * 2.9 X UO X 1.49 ' 

\ olts loss to motors = -r^ = 4.75. 

Volts at primaries of transformers for motors = 1.05x9 X (110 + 4.75) = 1084. 

Volts on secondaries of lighting transformers = = 105.2. 

l.yjd X l" 
Watts at primaries of motor transformers = 
21,940 X 1.029 



.97 
Watts at primaries of lighting transformers 
1500 X .5 X 105.2 



== 23,200. 
aers = 
= 81,340. 



.97 

Total watts delivered at transformers = 23,200 + 81,340 = 104,540. 
Power factor of load is 

23,200 X .80 + 81,340 X .95 _ 

104,540 — ' ' 



132 CONDUCTORS. 



CM. = ^ i y x2610 = 175,750. 

"•5000 v 104 ^40 
Taking No. 000 B. and S. wire = 167,805 CM., then P = ^ -^— , 

2610 = 4.21%. 
Drop in primary circuit = 

4.21 X 1076 1.49 X 80.8 + 1- 
100 X 104 

Voltage between outside lines at generator = 1076 + 68.5 = 1144.5 volts. 

104 540 
Current in main conductors = ztf^ 1 — ttz = 106.7 amperes. 
107b X .91 

90 Of)A 

Primary teazer wire = "1/ X 167,805 = 37,240 CM. required 
Use No. 4 B. and S., with a section of 41,742 CM. 

THREE-WIRE SECONDARY FOR MOTORS AND LIGHTS. 60 CYCLES. 

(See Fig. 26.) 

Example : Distance from generator to transformers, 1000 ft. Ratio of 
main transformers, 9 to 1. The load consists of 1000 half-ampere, 110 volt- 
lamps, and four 10-H. P. induction-motors. The distance from transformers 
to motors is 200 ft., and the length of three-wire lighting feeders is 150 ft. 
The drop in lighting feeders and motor circuits to be about 10 volts. Loss 
in primary circuit to be 3%. 

Lamp load = .5 x HO X 1000 = 55,000 watts. 

P X E X M 

Assuming a per cent loss such that — — — will be about 10 volts, then 

c.M.=im^x^ = iaa,««.c.M. 

Taking No. 000 B. and S. wire with an area of 167,805 CM., we have P — 
150X55,000 xM00=2>4t 



167,805 X 220 2 

•cr i. i • i-"-iU- * a 2.44x220x1.49 
Volts loss m lighting feeders = — — = 8. 

Voltage at transformers = 220 + 8 = 228. 

Size of neutral feeder = — '— — = 55,935 CM., or about No. 2 B. and S. 

area, 66,373 CM. 
Input on each 10 H. P. motor at full-load with an efficiency of 84% is equal to 

10 *™= 8,881 watts. 

P y T? *y ]\£ 

Assuming a per cent loss such that — is about 8 volts, we have, 

c - M -=^s= 338o = 35 > 5ooc - M - 

No. 5 B. and S. = 33,102 CM. taken for section of motor leads. 
„ 200 X 8881 X 3380 



33,102 X 220 2 



= 3. 



3 - 75 X 220 X 1 
Volt loss to motors = ^oo" — 8 - 25, 

The motor load is 4 x 8881 X 1.0375 = 36,800 watts. 
Tbe lighting load is 55,000 x 1.0244 = 56,340 watts. 
56.340 + 36,800=93,140 watts. 

93 140 
Assuming transformer efficiencies of 97%, — ^=— = 96,000 watts load on 

transformers. 

The voltage at the transformer primaries, allowing 4% drop in trans- 
formers, is 228 X 9 X 1.04 = 2134. 



■M 



APPLICATION OF GENERAL WIRING FORMULAE. 133 

_ 1000 X 96,000 56,340 X 2400 + 36,800 X 33 80 _ 

' '"" 3X21342 X 96^000 — 19,000 O.M. 

No, 7 B. and S. = 20,816 CM. 

19,000 
F ~ 20,816 x3 - 2 - 7 - 
2 74 X 2134 X 1 
Volts loss in line = — = 58.5. 2134 -f 58.5 = 2192.5 volts at 

generator. The section of theprimary teazer wire would be — — X 19,000 =7500 

CM., but this is too small for outside work, hence we would use two No. 7 
wires, and one No. 8 wire for the primary circuit. 



Three-Phase System. ©O Cycles. 

three-wire transmission. (See Figs. 27 and 28.) 

Example. — Required : the size of conductors and drop in line to transmit 
5000 H.P. Z\ miles, with a loss equal to about 10% of the delivered power. 
"Voltage between lines at receiving end, 5000. Power factor of load, 85%. 

5280 X 3.5 X 5000 X 746 

°- M - = 10^5000^ X 1500=413,582C.M. 

Two No. 0000 B. and S. wires per branch would answer ; but the drop in 
1.46 
voltage will be only — — , or 73.3% as great for the same loss of power, if we 

take four No. B. and S. wires in parallel, or a line of twelve No. B. and 
8. wires in a,l. The loss will beP = ^xm^T^ X 15 °° = 9 ' 79 * 
of delivered power, i.e., .0979 X 5000 = 489.5 H.P. lost in line. 

^ u -, ,. • i- 9-79 X 5000 X 1.46 „„_ 1-L 
Volts lost in line == = 715 volts. 

Voltage at generator = 5000 + 715 = 5715 volts. 

5000 X 746 
Current in line = — --— — X .659 = 506.5 amperes. 



FOUR-WIRE SECONDARY SYSTEM. (See FlG. 29.) 

Example. — Required: the size of conductors from transformers to the 
distributing centre of a four-wire secondary system for lights and motors. 
The load consists of four 15 H.P., 200 volt-induction motors, and 750 half- 
ampere, 16 c.p., 115 volt-limps. Length of secondary wiring from trans- 
formers to distribution centre, 600 ft. About 15 volts drop on lighting 
circuits from transformers to distributing centre. Efficiency of motors, 85%. 
5 volts drop on circuits from distributing centre to motors. Voltage at dis- 
tributing point between main lines is 205. Current in main lines for motors 
. 4 X 15 X 746 X .725 • 

1S ,.85X200 ~ 191 am P ereS ' 

Current from transformers for lamps is 

(750 X .5 X 115) X -607 

* 20^ — 131 am P eres - 

Total current from transformers is 131 -f- 191 = 322 amperes. 

W 
For motors, 191 = — X .725. W= 54,000. 
205 

W 

For lamps, 131 = ^ X .607. W = 44,240. Total watts == 98,240. 

Taking for trial two No. B. and S. wires in parallel for each of the main 



134 CONDUCTORS. 

conductors, as preferable to one No. 0000, then P — — 60 ° X 98,240 

2 X 105,592 X 205 2 
1200 x 44,240 + 1690 X 54,000 

98,249 - 9 - 75 ' 

Volts loss in lines = 9 ^ X 205 X i^ 6 = 29.2. 
100 
Volts at transformers between main lines = 231.4. 
Actual drop between main conductors and neutral to distributing point : 

29.2 x ^=16.8 volts. 



The section of the neutral conductor should be about 



131 X 2 X 105,592 



322 — 

86,000 CM. We may use one No. 1 B. and S. wire, with a section of 83,694 
CM. for the neutral. 

Two-Phase System. OO Cycles. 

FOUR- WIRE TRANSMISSION. (See FlG. 29.) 

Example. — Required : the size of conductors and drop in line to transmit 
5000 H.P. 3| miles, with a loss equal to about 10% of the delivered power. 
Voltage between lines at receiving end, 5000. Power factor of load is 85%. 
„ ,.. 5280 X 3.5 X 5000 X 746 

C - M ' = 10X5000* X 1500 = 413,580 CM. 

Taking four No. B. and S. wires in parallel, the line will consist of six- 
teen No. B. and S. wires in all. The loss will be P = 52 f ^l^* 50W * I* 6 

4 X 105 592 X 5000 
X 1500 = 9.79% of delivered power, or .0979 x 5000=489.5 H.P. lost in the line. 
Volts lost m line — 

PxExM 9.79x5000x1.46 m „ ,, 

ioo = ioo = 715 volts * 

Volts at generating end of line = 5715. 

Current in line = -X-- — X .588 = 438.6 amperes. 

Alternating-Current Arcs. 

Power factor is about .75. Calculate wire for apparent watts, not real 
watts. 

Chart ami Table for calculating- Alternating-Current 
lanes. 

Ralph D. Mershon, in American Electrician. 

The accompanying table, and chart on page 137 include everything neces- 
sary for calculating the copper of alternating-current lines. 

The terms, resistance volts, resistance E.M.F., reactance volts, and react- 
ance E.M.F., refer to the voltages for overcoming the back E.M.F.'s due to 
resistance and reactance respectively. The following examples illustrate 
the use of the chart and table. 

Problem. — Power to be delivered, 250 k.w.; E.M.F. to be delivered, 2000 
volts; distance of transmission, 10,000 ft.; size of wire, No. 0; distance be- 
tween wires, 18 inches ; power factor of load, .8 ; alternations, 7200 per min- 
ute. Find the line loss and drop. 

The power factor is that fraction by which the apparent power or volt-am- 
peres must be multiplied to give the true power or watts. Therefore the 

apparent power to be delivered is -^1 = 312.5 apparent k.w., or 312,500 

volt-amperes, or apparent watts. The current, therefore, at 2000 volts will be 
312 500 

— - ■■ — = 156.25 amperes. From the table of reactances, under the heading 
2000 

" 18 inches," and corresponding to No. wire, is obtained the constant, .228. 
Bearing the instructions of the table in mind, the reactance volts of this 



APPLICATION OF GENERAL WIRING FORMULAE. 135 

line are 156.25 (amperes) x 10 (thousands of feet) X .228 = 356.3 volts, which 
are 17.8 per cent of the 2000 volts to be delivered. 

From the column headed " Resistance Volts," and corresponding to No. 
wire, is obtained the constant .197. The resistance volts of the line are, 
therefore, 156.25 (amperes) x 10 (thousands of feet) X .197 = 307.8 volts, which 
are 15.4 per cent of the 2000 volts to be delivered. 

Starting, in accordance with the instructions of the sheet, from the point 
where the vertical line, which at the bottom of the sheet is marked " Load 
Power Factor .8," intersects the inner or smallest circle, lay off horizontally 
and to the right the resistance E.M.F. in per cent (15.4), and "from the 
point thus obtained," lay off vertically the reactance E.M.F. in per cent 
(17.8). The last point falls at about 23 per cent, as given by the circular arcs. 
This, then, is the drop in per cent of the E.M.F. delivered. The drop in per 

23 
cent of the generator E.M.F. is, of course, ■-- , . = 18.7 per cent. 

100-j-2o 

The resistance volts in this case being 307.8, and the current 156.25 am- 
peres, the energy loss is 307.8 x 156.25 = 48.1 k.w. The percentage loss is 

48 1 
250 -L 48 1 = 16,1 ' Tlierefore » for tne problem taken, the drop is 18.7 per cent, 
and the energy loss is 16.1 per cent. 

If the problem be to find the size of wire for a given drop, it must be solved 
by trial. Assume a size of wire, and calculate the drop in the manner above 
indicated ; the result in connection with the table will show the direction 
and extent of the change necessary in the size of wire to give the required 
drop. 

The table is made out for 7200 alternations per minute, but will answer 
for any other number. For instance, for 16,000 alternations, multiply the 
reactances by 16000 -f- 7200 = 2.22. 

As an illustration of the method of calculating the drop in a line and trans- 
former, and also of the use of the table and chart in calculating low-voltage 
mains, the following example is given : — 

Problem. — A single-phase, induction motor is to be supplied with 20 am- 
peres at 200 volts ; alternations, 7200 per minute ; power factor, .78. The 
distance from transformer to motor is 150 ft., and the line is No. 5 wire, 6 
inches between centres of conductors. The transformer reduces in the ratio 
2000 : 200, and has a capacity of 25 amperes at 200 volts ; when delivering this 
current and voltage, its resistance E.M.F. is as 2.5 per cent, and its reactance 
E.M.F. 5 per cent, both of these constants being furnished by the makers. 
Find the drop. 

The reactance of 1000 ft. of circuit, consisting of two No. 5 wires, 6 inches 

150 
apart, is .204. The reactance-volts, therefore, are .204 X zr^. X 20= .61 volts. 

150 
The resistance-volts are .627 X r^ X 20 = 1.88 volts. At 25 amperes, the re- 
sistance-volts of the transformers are 2.5 per cent of 200, or 5 volts. At 20 

20 
amperes they are — of this, or 4 volts. Similarly, the transformer reactance 

volts at 25 amperes are 10, and at 20 amperes are 8 volts. The combined re- 
actance-volts of transformer and line are 8 + .61 = 8.61, which is 4.3 per cent 
of the 200 volts to be delivered. The combined resistance-volts are 1.88 + 4, 
or 5.88, which is 2.94 per cent of the E.M.F. to be delivered. Combining these 
quantities on the chart with a power factor of .78, the drop is 5 per cent of 

5 
the delivered E.M.F., or — = 4.8 per cent of the impressed E.M.F. The 

transformer must therefore be supplied with 2000+ .952 = 2100 volts, in order 
that 200 volts shall be delivered to the motor. 

To calculate a four-wire, two-phased transmission circuit, compute, as 
above, the single-phased circuit required to transmit one-half the power at 
the same voltage. The two-phase transmission will require two such 
circuits. 

To calculate a three-phase transmission, compute, as above, a single-phase 
circuit to carry one-half the load at the same voltage. The three-phase 
transmission will require three wires of the size obtained for the single-phase 
circuit, and with the same distance (triangular) between centres. 

By means of the table calculate the Resistance- Volts and the Reactance- 



136 



CONDUCTORS. 



Volts in the line, and find what per cent each is of the E.M.F. delivered at 
the end of the line. Starting from the point on the chart where the vertical 
line corresponding with power factor of the load intersects the smallest 
circle, lay off in per cent the resistance E.M.F. horizontally and to the right ; 
from the point thus obtained lay off upward in per cent the reactance E.M.F. 
The circle on which the last point falls gives the drop in per cent of the 
E.M.F. delivered at the end of the line. Every tenth circle-arc is marked 
with the per cent drop to which it corresponds. 



Size 

of 

Wire 

B.&S. 


7* ? 
-§5 


<W CD 

° 3 

rt CD 

>^ 

^^ 

II 


CD 

as 

> 

t 
ft 


Reactance-Volts in 1000 ft. of Line (=2000 ft. of Wire) 
for One Ampere (V M ean Square) at 7200 Alternations 
per Minute for the Distance given between Centres of 
Conductors. 




&>1 


5 


1" 


1" 


3" 


6" 


9" 


12" 


18" 


24" 


30" 


36" 


0000 


639 


.098 


.046 


.079 


.111 


.130 


.161 


.180 


.193 


.212 


.225 


.235 


.244 


000 


507 


.124 


.052 


.085 


.116 


.135 


.167 


.185 


.199 


.217 


.230 


.241 


.249 


00 


402 


.156 


.057 


.090 


.121 


.140 


.172 


.190 


.204 


.222 


.236 


.246 


.254 





319 


.197 


.063 


.095 


.127 


.145 


.177 


.196 


.209 


.228 


.241 


.251 


.259 


1 


253 


.248 


.068 


.101 


.132 


.151 


.183 


.201 


.214 


.233 


.246 
.252 


.256 


.265 


2 


201 


.313 


.074 


.106 
.112 
.117 


.138 


.156 


.188 


.206 


.220 


.238 


.262 


.270 


3 


159 


.394 


.079 


.143 
.149 


.162 


.193 


.212 


.225 


.244 


.257 


.267 


.275 


4 


126 


.497 


.085 


.167 


.199 


.217 


.230 


.249 


.262 


.272 


.281 


5 


100 


.627 


.090 


.121 


.154 


.172 


.204 


.223 


.236 


.254 


.268 


.278 


.286 


6 


79 


.791 


.095 


.127 


.158 


.178 


.209 


.228 


.241 


.260 


.272 


.283 


.291 


7 


63 


.997 


.101 
.106 


.132 
.138 


.164 


.183 
.188 


.214 


.233 


.246 


.265 


.278 


.288 


.296 


8 


50 


1.260 


.169 


.220 


.238 


.252 


.270 


.284 


.293 


.302 



BELL WIRING. 



13T 




.5 .6 .1 

Load Power Factors 



Fig. 30. 



10 .20 30 

" Drop in Percent of 

:E.M.F. Delivered 



BEIiK. WIROG. 

The following diagrams show various methods of connecting up-call hells 
for different purposes, and will indicate ways in which incandescent lamps 
may also he connected to accomplish different results. 



§2 F¥ 



Fig. 31. One Bell, operated by one Fig 32. One Bell, operated by Two 
Push. Pushes. 



138 



CONDUCTORS. 



* f- 



Fig. 33. Two Bells, operated by One 
Push. 



Fig. 34. Two Bells, operated by 
Two Pushes. 



When two or more bells are required to ring from one push, the common 
practice is to connect them in series, i.e., wire from one directly to the next, 
and to make all but one single-stroke ends. Bells connected in multiple 
arc, as in diagram No. 24, give better satisfaction, although requiring more 
wire. 



Fig. 35. Three-line Factory Call. 
A number of Bells operated by 
any number of pushes. All bells 
rung by each push. 



Fig. 36. Simple button, Three- 
line Return Call. One set of 
battery. 



Gd-# 



Fig. 37. Simple Button, Two-Line 
and Ground Return Call. One set 
of Battery. 



Fig. 38. Two-Line Return Call. 
Illustrating use of Return Call 
Button. Bells ring separately. 



G 

Fig. 39. One-Line and Ground Return 
Call. Illustrating use of Return Call- 
Button. Bells ring separately. 



Fig. 40. Simple Button, Two- 
Line Return Call. Bells ring 
together. 




Fig. 41. Simple-Button, One-Line 
and Ground Return Call. Bells 
ring together. The use of com- 
plete metallic circuit in place of 
ground connection is advised in 
all cases where expense of wire 
is not considerable. 



Fig. 42. Four Indication Annuncia- 
tor. Connections drawn for two 
buttons only. A burglar alarm cir- 
cuit is similar to the above, but 
with one extra wire running from 
door or window-spring side of bat- 
tery to burglar alarm in order to 
operate continuous ringing attach- 
ment. 



BELL WIRING. 



139 



it 



c 



Fig. 43. Four Indication Annuncia- 
tor, with extra Bell to ring from one 
Push only. Illustrating use of 
three-point button. 



J||~l§ 



Fig. 44. Acoustic Telephone with 
Magneto Bell Return Call. Ex- 
tension Bell at one end of line. 



In running lines between any two points, use care to place the battery if 
SSK SttSSi ^?"±^^T±°l th ° line ' as a ^ leakage in the^'ir? 



cuit will not then weaken the battery. 




Fig. 45. Diagram of Burglar- Alarm Mat, two Bells, 
one Push and Automatic Drop ; all operated by one 
battery. Both bells ring from one push or mat, as 
desired, by changing the switch. 



When mat is to be used, throw it into the circuit 
by the switch, so that when the circuit is closed by a 
person stepping on the mat, the automatic drop will 
keep it closed, and both bells will continue to ring 
until the drop is hooked up again. 



^Aft-LlttH'f WIROG. 





Fig. 46. Pendent and Automatic Gas- Fig. 47. Pendent Gas-Lighting Cir- 
Lighting Circuit, with Switch-board. cuit, with Switch-board, Relay, 

and Tell-Tale Bell. 



.^M_ft_£> 




Fig. 48. Diagram showing 
arrangement of circuits 
for Fire-Alarm or District- 
Messenger Service. 



Fig. 1 represents the engine-house or cen- 
tral station containing the local or open cir- 
cuit (8;. 

2 Represents the main or closed circuit on 
which is located the fire-alarm or messenger 
boxes (9). 

3 Is the automatic register and winder. 

4 Is the electro-mechanical gong. 

5 Is the battery of open-circuit cells. 

6 Is the battery of closed-circuit cells. 

7 Is the relay and relay bell. 

Instead of, or in addition to, the gong (4) s 
may be used a mechanical tower strike. 



PROPERTIES OF CONDUCTORS. 

Pure and Soft Copper. 

Specific gravity, pure annealed, at 60° F 8.89 lbs. 

Cubic foot weighs 555 lbs. 

Cubic inch weighs 32 lbs. 

1,000 foot 1 inch square rod weighs 3,851 lbs. 

Tensile strength at 100° F. per square inch 23,366 lbs. 

Specific resistance 1 cubic centimeter 0° C 000001594 ohm. 

Resistance 1 cubic inch 15.5° C. or 60° F 0000006774 ohm. 

Resistance 1 foot of 1 square inch section 20° C 000008128 ohm. 

Resistance 1 mil-foot 0° C 9.59 ohms. 

Weight per mile of copper wire is 

(dia. in mils) 2 
62^ 
Resistance per mile in ohms, of pure copper at 60° F., is 

54,892 

(dia. in mils) 2 

Specific conductivity of pure copper is 100, commercial copper runs from 96 
to 102 per cent of the standard. 

Percentage of conductivity is found by measuring the resistance of a sample 
of the same length and weight as the standard, and at the same tem- 
perature, then if R =. resistance of standard, and r =z the resistance 

, 100 x R , .. .. 

of sample, = per cent conductivity. 

Percentage Conductivity of any Sample. 

The percentage conductivity of any sample of a conductor, as referred to 
a standard, can be determined as follows : — 

Let R = resistance of a unit weight and length of the standard, at tempera- 
ture t, from tables. 
I = length of wire to be tested, 
to =. weight of wire to be tested, 
r = computed resistance of a pure standard copper wire of the same 

dimensions and temperature as the test sample. 
r x =. observed resistance at temperature t of the wire under test in ohms. 
Then as the resistance of a conductor is directly proportional to its length, 
and inversely proportional to its weight per unit of length (its cross-section), 

'Rl* , 

r — ohms. 

w 

By actual test, the resistance of the wire having been found to be r' at tem- 
perature t, then 

r' : r : : 100 : x 

and the percentage of conductivity of tbe wire is 

100 r 



Rise of Resistance witn Temperature. 

The resistance of conductors is not a linear function of the temperature, 
and hence its variation with the temperature must, for very precise work, 
be represented in the ordinary formula : — 

140 



RISE OF RESISTANCE. 



141 



R = r (1 + a t ± b P) 
Where R = resistance at the temperature t, 
r = resistance at 0° C, 
t = temperature in degrees C, 
a and b = numerical constants from tahle below. 

The following values of the constants have been found, but they are really 
ipplicable to the original samples under test only : — 



Metals (very pure) 

Mercury 

German silver (Cu 60 -Zn 26 — Ni 14) . . 
Platinum silver (Pt 67 — Ag 33) . . . . 
Platinoid (Cu 59 — Zn 25.5 — Ni 14 — W 55) 
Silver gold 



.00382 


+.0000126 


000882 


—.000000362 


.000443 


+.000000152 


.00031 


" 


.00021 


" 


.0006999 


—.000000062 



For ordinary calculations the formula may be written and used as fol- 
lows : — 

R = r (1 + at) 

the values of a being given in the following table : — 



Metal. 


a 


Silver 


.00377 




.00388 


Gold 


.00365 




.00390 




.00247 




.00453 


Tin 


.00365 




.00387 




.00389 




.00354 




.00088 


German silver 


.00028 to .00044 



Tbe following table gives the value of the principal practical units of resis- 
tance which existed previous to the establishment of the International Units. 



Unit 


International 
ohm. 


B.A. 

OHM. 


Legal ohm 

1884. 


SlEMENS'S 
OHM. 


International ohm 
B. A. ohm . . . 

Legal ohm . . " . 
Siemens 's ohm . . 


1. 

0.9866 
0.9972 
0.9407 


1.0136 
1. 

1.0107 
0.9535 


1.0028 
0.9894 
1. 
0.9434 


1.0630 
1.0488 
1.0600 
1. 



Thus to reduce British Association ohms to international ohms we divide 
by 1.0136, or multiply by 0.9866 ; and to reduce legal ohms to international 
ohms we divide by 1.0028, or multiply by 0.9972, etc. 



142 



PROPERTIES OF CONDUCTORS. 



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143 



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e as follows : M 
. Resistance in 
oper = 0.1469 B. A 
.14365 B. A. U.@ 
141729 internatio 
, and 80° 0., 1.07 


nt digi 

nit, rep 

or A. 

earest 


§ SccR 


h signifi 
n half a 
heB. & 
ich, the 


SSoOoo 


"Ex!.. -rH 


computed 
copper = 8. 
ard drawn c 

20° C, 50~ 


the fou 
t to wit 
eters of 
= 0.005 


O O rtCD 
+S CD Ceo 


has been 
gravity of 
amme of h 
soft 
soft 
stance for 
6 gramme 

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146 



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150 



PROPERTIES OF CONDUCTORS. 



UARD.DRAWX COPPER TElECRiPH WIRE 

(J. A. Roebling's Sons Co.) 
Furnished in half-mile coils, either bare or insulated. 











Approximate 




Resistance in 


Breaking 


Weight per 
Mile. 


Size of E. B. B. 


SizeB. &S. 


Ohms 


Strength. 


Iron Wire 


Gauge. 


per Mile. 


Pounds. 


equal to 










Copper. 


9 


4.30 


625 


209 


2 1? 


10 


5.40 


525 


166 


3 § 


11 


6.90 


420 


131 


4 1 


12 


8.70 


330 


104 


6 t 


13 


10.90 


270 


83 


6^3 


14 


13.70 


213 


66 


9 p 


15 


17.40 


170 


52 


16 


22.10 


130 


41 


10 £ 

a 



In handling this wire the greatest care should he observed to avoid kinks, 
binds, scratches, or cuts. Joints should be made only with Mclntire Con- 
nectors. 

On account of its conductivity being about five times that of Ex. B. B. 
Iron Wire, and its breaking strength over three times its weight per mile, 
copper may be used of which the section is smaller and the weigbt less than 
an equivalent iron wire, allowing a greater number of wires to be strung on 
the poles. 

Besides this advantage, the reduction of section materially decreases the 
electrostatic capacity, while its non-magnetic character lessens the self-in- 
duction of the line, both of which features tend to increase the possible 
speed of signalling in telegraphing, and to give greater clearness of enuncia- 
tion over telephone lines, especially those of great length. 



I£AD.EACA§ED ANTI-INDUCTION TELEPHONE 
AND T£.LE»IIAP1I CABLES. 



(Roebling's.) 



Plain Cables, Lead 


Fob Metallic 


Fob Telegbaph 


Encased. 


Cibcuit. 


Cibcuits. 


No. of 


Size Wire 


No. of 


Size Wire 


No. of 


Size Wire 


Wires. 


B.&S. Gauge. 


Pairs. 


B.&S. Gauge. 


Wires. 


B.&S. Gauge. 


4 


18 


5 


18 


3 


14 


7 


18 


15 


18 


4 


14 


10 


18 


25 


18 


7 


14 


50 


18 


50 


18 


10 


14 


100 


18 


75 


18 


20 
50 
100 


14 
14 
14 



COPPER WIRES. 



151 



TABID OE DIMENSIONS. WEIGHT, AI¥» RE< 
SISTANCE OF PURE COPPER WIRE, 

(Edison or Circular Mil ©aug-e.) 









a .9 


Weight. Sp. gr. 8.889. 






g • " ^ 






£,& 


11 


<L> 


lis 


Hi 8 


o 

o 

u 


a 


H ^ 


o 


s«u> 


rt i— 1 


ft 

CO 


02 


3 


3,000 


12.5 


54.78 


.009084 


2.597 


5 


5,000 


18.3 


70.72 


.015139 


7.214 


8 


8,000 


26.0 


89.45 


.024220 


18.464 


12 


12,000 


35.2 


109.55 


.036328 


41.538 


15 


15,000 


41.6 


122.48 


.045410 


64.902 


20 


20,000 


51.6 


141.43 


.060548 


115.372 


25 


25,000 


61.0 


158.12 


.075682 


180.278 


30 


30,000 


70.0 


173.21 


.090817 


259.722 


35 


35,000 


78.6 


187.09 


.105955 


353.340 


40 


40,000 


86.8 


200.00 


.121082 


461.440 


45 


45,000 


94.9 


212.14 


.136227 


584.098 


50 


50,000 


102.7 


223.61 


.151357 


721.026 


55 


55,000 


110.3 


234.53 


.166501 


872.547 


60 


60,000 


117.7 


244.95 


.181625 


1,038.258 


65 


65,000 


125.0 


254.96 


.196772 


1,218.586 


70 


70,000 


132.1 


264.58 


.211901 


1,413.264 


75 


75,000 


139.1 


273.87 


.227043 


1,622.457 


80 


80,000 


146.0 


282.85 


.242176 


#,845.952 


85 


85,000 


152.8 


291.55 


.257303 


2,083.759 


90 


90,000 


159.5 


300.00 


.272434 


2,336.405 


95 


95,000 


166.1 


308.23 


.287587 


2,603.046 


100 


100,000 


172.6 


316.23 


.302709 


2,884.082 


110 


110,000 


185.4 


331.67 


.332991 


3,489.958 


120 


120,000 


198.0 


346.42 


.363267 


4,153.433 


130 


130,000 


210.2 


360.56 


.393527 


4,874.226 


140 


140,000 


222.2 


374.17 


.423797 


5,652.899 


150 


150,000 


234.0 


387.30 


.454061 


6,484.573 


160 


160,000 


245.6 


400.00 


.484328 


7,383.042 


170 


170,000 


257.0 


412.32 


.514622 


8,335.525 


180 


180,000 


268.3 


424.27 


.544884 


9,344.686 


190 


190,000 


279.4 


435.89 


.575140 


10,411.241 


200 


200,000 


290.4 


447.22 


.605427 


11,536.681 


220 


220,000 


312.0 


469.05 


.665975 


13,959.567 


240 


240,000 


333.0 


489.90 


.726498 


16,612.114 


260 


260,000 


353.5 


509.91 


.787058 


19,496.997 


280 


280,000 


373.7 


529.16 


.847605 


22,612.233 


300 


300,000 


393.6 


547.73 


.908140 


25,957.464 


320 


320,000 


413.1 


565.69 


.968672 


29,533.696 


340 


340,000 


432.3 


583.10 


1.029214 


33,340.181 


360 


360,000 


451.3 


600.00 


1.089738 


37,376.652 



1 Mil Foot s= 9.718 B. A. Units @ 0° C. (Dr. Matthiessen.) 



152 



PROPERTIES OF CONDUCTORS. 



TABLE OF DIMENSIONS, WEIGHT, 4TVI> RESIS- 
TANCE ©E PURE COPPER WIRE — Continued. 

(Edison or Circular Mil Gauge.) 



Length. 



Resistance. Legal ohms at 75° Fahr, 



110.087 

66.054 

41.288 

27.527 

22.022 

16.516 

13.213 

11.011 

9.4381 

8.2589 

7.3407 

6.6069 

6.0060 

5.5059 

5.0820 

4.7192 

4.4044 

4.1*2 

3.8865 

3.6706 

3.4773 

3.3035 

3.0031 

2.7528 

2.5411 

2.3596 

2.2023 

2.0647 

1.9432 

1.8353 

1.7387 

1.6517 

1.5016 

1.3765 

1.2706 

1.1798 

1.1012 

1.0323 

.9716 

.9177 



285.9 
476.5 
762.3 
1,143.4 
1,429.2 
1,905.7 
2,382.0 
2,859.9 
3,334.9 
3,811.0 
4,287.7 
4,763.8 
5,240.5 
5,716.5 
6,192.9 
6,669.4 
7,146.0 
7,622.3 
8,098.4 
8,574.7 
9,051.6 
9,527.6 
10,480.6 
11,433.6 
12,386.0 
13,338.7 
14,291.3 
15,243.9 
16,197.4 
17,149.9 
18,102.1 
19,055.4 
20,961.1 
22,866.0 
24,772.1 
26,677.8 
28,583.1 
30,488.3 
32,393.8 
34,298.7 



.3850405 

.1386225 

.0651602 

.0240743 

.0154178 

.0086664 

.0055470 

.0038522 

.0028301 

.0021671 

.0017120 

.0013868 

.0011467 

.00096315 

.00082057 

.00070758 

.00061635 

.00054172 

.00047990 

.00042807 

.00038415 

.00034673 

.00028656 

.00024070 

.00020514 

.00017690 

.00015409 

•00013544 

.00011995 

.00010701 

.00009604 

.00008667 

.00007163 

.00006019 

.00005129 

.00004422 

.00003852 

.00003386 

.00002099 

.00002675 



.003497600 
.002098640 
.001311780 
.000874578 
.000699663 
.000524745 
.000419807 
.000349840 
.000299863 
.000262400 
.000233227 
.000209914 
.000190821 
.000174931 
.000161465 
.000149937 
.009139938 
.000131193 
.000123480 
.000116622 
.000110477 
.000104960 
.000095410 
.000084460 
.000080730 
.000074970 
.000069997 
.000065600 
.000061735 
.000058309 
.000055242 
.000052478 
.000047707 
.000043733 
.000040368 
.000037484 
.000034986 
.000032799 
.000030870 
.000029155 



1 Mil Foot = 9.718 B. A. Units @ 0° 0. (Dr. Matthiessen.) 



CAPACITY OF COPPER WIRES. 153 

§AFE CARRYING CAPACITY OF COPPER 

WIRES. 

Below will be found the formulae of Forbes and Kennelly for safe carrying 
capacity of copper conductors. The results, which would be obtained by 
using these formulae, have been somewhat modified in practice, and the 
reader is referred to the tables in the "National Code" for capacities 
recommended by the underwriters. 

Size of Conductors. 

(Prof. G. Forbes.) 

Rare Overhead "Wires. — The relation between the diameter of a 
conductor and the current it can safely carry without over-heating is 



*=tf 



TT 2 JI 
D*t 



iB X.24 
Where 7= Current in amperes. 

D = Diameter of wire in centimeters. 

t = Excess of temperature C. of wire over the air. 
H =r Coefficient of radiation and convection = .0003. 
B = Specific electrical resistance of material per c. cm. at the lim- 
iting temp. 
.24 = Calories in a Joule. # 

Insulated Overhead "Wires. — For gutta-percha and india-rubber 
insulation, 

. tt, JcD, 2 ..... 3D., 



V l ^ 1 + 3 A log 6 §( 



Where D 1 =r Diameter of conductor. 

Z) 2 ■=. Diameter of insulated cable. 
t = Excess of temperature of conductor over air. 
k — Heat conductivity of insulator ; for G.-P. = .00048 ; for I.-R. = 
.00041. 

Kennelly's Rule for the Safe Diameter of an Insulated 
Paneled IVire. 

If the limiting safe diameter of an insulated paneled wire be such that 
twice the proposed full load upon it shall only raise its temperature 40° C, 
then the best formula is 

d = .0147 li, 
d being in inches and I in amperes ; or approximately 

Heating- of Rare Conductors by a Current. 

The temperature to which a bare copper wire freely suspended in still air 
will be raised when traversed by a current is approximately 

T°= J X 90,000 4- t°, 

where 

T° =z temperature of wire in F°. 
t° = temperature of air in F°. 
7 = current in amperes. 
d = diameter of wire in mils. 
For a given presumable maximum elevation of temperature the requisite 
diameter is approximately 



<2 = 45 



1/ To — t° 



154 



PROPERTIES OF CONDUCTORS. 



■ HO* WIRE. 
Iron. 

Specific gravity „ 7.7 

Cubic foot weighs 480 lbs. 

Cubic inch weighs 2779 lb. 

Tensile strength per square inch 50,000 to 60.000 lbs. 

Specific resistance 1 cubic centimeter at 0° C. . .0000095 ohms. 

Resistance per mil foot 58 ohms. 

Steel. 

Specific gravity 7.932 

Cubic foot weighs 490 lbs. 

Cubic inch weighs 2834 1b. 

Tensile strength per square inch 55,000 to SO.OOO lbs. 

Specific resistance 1 cubic centimeter at 0° C. . .0000133 ohms. 

Resistance per mil foot 82 ohms 

The above items are for the metals as metals, and not when in wire. Re- 
sistance of iron wire varies so much, by reason of drawing and hardening, 
that it is not practicable to state specific resistances, weights, and strengths. 

The following tables give approximate averages. 

GALVANIZED IRON WIBE EO« XEIECiRAPH 
Ol) TELEPHONE LINEi. 

(Trenton Iron Co.) 

Weight per Mile-Ohm. — This term is to be understood as distin- 
guishing the resistance of material only, and means the weight of such 
material required per mile to give the resistance of one ohm. To ascertain 
the mileage resistance of any wire, divide the " weight per mile-ohm" by 
the weight of the wire per mile. Thus in a grade of Extra Best Best, of 
which the weight per mile-ohm is 5,000, the mileage resistance of No. 6 
(weight per mile 525 lbs.) would be about 9i ohms ; and No. 14 steel wire, 
8500 lbs weight per mile-ohm (95 lbs. weight per mile), would show about 69 
ohms. 

Sizes of Wire used in Telegraph and Telephone Eines. 

No. 4. Has not been much used until recently ; is now used on important 
lines where the multiplex systems are applied. 

No. 5. Little used in the "United States. 

No. 6. Used for important circuits between cities. 

No. 8. Medium size for circuits of 400 miles or less. 

No. 9. For similar locations to No. 8, but on somewhat shorter circuits ; 
until lately was the size most largely used in this country. 

Nos. 10, 11. For shorter circuits, railway telegraphs, private lines, police 
and fire alarm lines, etc. 

No. 12. For telephone lines, police and fire alarm lines, etc. 

Nos. 13, 14. For telephone lines, and short private lines ; steel wire is 
used most generally in these sizes. 

The coating of telegraph wire with zinc as a protection against oxidation 
is now generally admitted to be the most efficacious method. 

The grades of line wire are generally known to the trade as " Extra Best 
Best" (E. B. B.), " Best Best" (B. B.)", and " Steel." 

" Extra Best Best " is made of the very best iron, as nearly pure as any 
commercial iron, soft, tough, uniform, and of very high conductivity, its 
weight per mile-ohm being about 5,000 lbs. 

The " Best Best" is of iron, showing in mechanical tests almost as good 
results as the E. B. B., but not quite as soft, and being somewhat lower in 
conductivity ; weight per mile-ohm about 5.700 lbs. 

The Trenton " Steel " wire is well suited for telephone or short telegraph 
lines, and the weight per mile-ohm is about 6,500 lbs. 



TESTS OF TELEGRAPH WIRES. 



155 



The following are (approximately) the weights per mile of various sizes of 
galvanized telegraph wire, drawn by Trenton Iron Co.'s gauge : 



No. 4, 



10, 



11, 



12, 13, 14, 



Lbs. 720. 610. 525. 450. 375. 310 . 250. 200. 100. 125. 95. 



TESTi Of TEIEGRAPH WIRE. 

The following data are taken from a table given by Mr. Prescott relating 
to tests of E. B. B. galvanized wire furnished the Western Union Telegraph 
Co. : 







Wei 


ght. 




Resistance. 
Temp. 75.8° Fahr. 


&c 










T3 








Si 

'% 

o 

N 

w 


cS 03 

5° 


o 

o 

"c3 


6 

u 
<s 

Qi 


5 

J o 

t*s~r 

fl 03 
03 ft 

OP 
03 

Eh 


g 
o 

03 

03 
03 


•03 

s 

03 


OS* 1 ' . 

'-G "S 






o 


Ph 




^ 


o 




4 


.238 


1,043.2 


886.6 


6.00 


958 


5.51 




5 


.220 


891.3 


673.0 


7.85 


727 


7.26 




6 


.203 


758.9 


572.2 


9.20 


618 


8.54 


3.05 


7 


.180 


596.7 


449.9 


11.70 


578 


10.86 


3.40 


8 


.165 


501.4 


378.1 


14.00 


409 


12.92 


3.07 


9 


.148 


403.4 


304.2 


17.4 


328 


16.10 


3.38 


10 


.134 


330.7 


249.4 


21.2 


269 


19.60 


3.37 


11 


.120 


265.2 


200.0 


26.4 


216 


24.42 


2.97 


12 


.109 


218.8 


165.0 


32.0 


179 


29.60 


3.43 


14 


.083 


126.9 


95.7 


55.2 


104 


51.00 


3.05 



Joints in Xeleg-raph Wires. — The fewer the joints in a line the 
better. All joints should be carefully made and well soldered over, for a 
bad joint may cause as much resistance to the electric current as several 
miles of wire. 



WEIGHT 



-AJ¥» RESISTANCE OE eAIVAMZED 
IRO\ WIRE PER MILE. 



(Roebling.) 



Gauge. 
B. &S. 


Weight 
per 
Mile. 


Resistance. 
Ohms. 


Gauge. 
B. &S. 


Weight 
per 

Mile. 


Resistance. 

Ohms. 


6 
7 
8 
9 
10 


550 
470 
385 
330 
268 


10 
12.1 
14.1 
16.4 

20 


11 
12 
14 
16 


216 
170 
100 
62 


20 
32.7 
52.8 
91.6 



156 



PROPERTIES OF CONDUCTORS. 



SIZE, WEIGHT, LENGTH A]¥» STRENGTH OF 
IRON WIRE. 

(Trenton Iron Co.) 



PI 

2 <D 


05 .3 




<s> 




Tensile Strength (Ap- 


c w 


£ o^- 


O Pi 


proximately) of Char- 


® 5 
HO 


21 




o a 




coal Iron Wire in 
Pounds. 


-°.pi 

I 1 * 


So 


o -rH .S © 


+= o 

8 Ah 


►a 




Bright. 


Annealed. 


00000 


.450 


.15904 


1.863 


2,833.248 


12,598 


9,449 


0000 


.400 


.12566 


2.358 


2,238.878 


9,955 


7,466 


000 


.360 


.10179 


2.911 


1,813.574 


8,124 


6,091 


00 


.330 


.08553 


3.465 


1,523.861 


6,880 


5,160 





.305 


.07306 


4.057 


1,301.678 


5,926 


4,445 


1 


.285 


.06379 


4.645 


1,136.678 


5,226 


3,920 


2 


.265 


.05515 


5.374 


982.555 


4,570 


3,425 


3 


.245 


.04714 


6.286 


839.942 


3,948 


2,960 


4 


.225 


.03976 


7.454 


708.365 


3,374 


2,530 


5 


.205 


.03301 


8.976 


588.139 


2,839 


2,130 


6 


.190 


.02835 


10.453 


505.084 


2,476 


1,860 


7 


.175 


.02405 


12.322 


428.472 


2,136 


1,600 


8 


.160 


.02011 


14.736 


358.3008 


1,813 


1,360 


9 


.145 


.01651 


17.950 


294.1488 


1,507 


1,130 


10 


.130 


.01327 


22.333 


236.4384 


1,233 


925 


11 


.1175 


.01084 


27.340 


193.1424 


1,010 


758 


12 


.105 


.00866 


34.219 


154.2816 


810 


607 


13 


.0925 


.00672 


44.092 


119.7504 


631 


473 


14 


.080 


.00503 


58.916 


89.6016 


474 


356 


15 


.070 


.00385 


76.984 


68.5872 


372 


280 


16 


.061 


.00292 


101.488 


52.0080 


292 


220 


17 


.0525 


.00216 


137.174 


38.4912 


222 


165 


18 


.045 


.00159 


186.335 


28.3378 


169 


127 


19 


.040 


.0012566 


235.084 


22.3872 


137 


103 


20 


.035 


.0009621 


308.079 


17.1389 


107 


80 


21 

22 


.031 

.028 


.0007547 
.0006157 


392.772 
481.234 


13.4429 
10.9718 






S'Ssi a5 03 

cmo i" a 


23 


.025 


.0004909 


603.863 


8.7437 


24 


.0225 


.0003976 


745.710 


7.0805 


25 


.020 


.0003142 


943.396 


5.5968 


55 03 - £ =«o:^.a 


26 


.018 


.0002545 


1,164.689 


4.5334 


27 


.017 


.0002270 


1,305.670 


4.0439 


28 


.016 


.0002011 


1,476.869 


3.5819 




29 


.015 


.0001767 


1,676.989 


3.1485 


30 


.014 


.0001539 


1,925.321 


2.7424 


31 


.013 


.0001327 


2,232.053 


2.3649 


32 


.012 


.0001131 


2,620.607 


2.0148 


8 ® <w ^3 — .s 8 a u § 


33 


.011 


.0000950 


3,119.092 


1.6928 




34 


.010 


.00007854 


3,773.584 


1.3992 


35 


.0095 


.00007088 


4,182.508 


1.2624 


osg^lsgS'S ^ 


36 


.009 


.00006362 


4,657.728 


1.1336 


> 2^So^ d o 


37 


.0085 


.00005675 


5,222.035 


1.0111 


38 


.008 


.00005027 


5.896.147 


.89549 


39 


.0075 


.00004418 


6,724.291 


.78672 


40 


.007 


.00003848 


7,698.253 


.68587 



IRON WIRES. 



15 r , 



WEIGHTS OF IROIV AXn iTEEL WIRE. 







Weight per 1000'. 


No. 


Diameter in 

Mils. 






B. & S. 










Wrought Iron. 


Steel. 


0000 


460 


561 


566 


000 


409.64 


445 


449 


00 


364.8 


353 


356 





324.86 


280 


282 


1 


289.3 


222 


224 


2 


257.63 


176 


178 


3 


229.42 


139 


141 


4 


204.31 


111 


112 


5 


181.94 


87.7 


88.5 


6 


162.02 


69.6 


70.2 


7 


144.28 


55.2 


55.7 


8 


128.49 


43.8 


44.1 


9 


114.43 


34.7 


35 


10 


101.89 


27.5 


27.8 


11 


90.74 


21.8 


22 


12 


80.81 


17.3 


17.5 



GAIVAlflZED *l«.\ t I 6TRAKD. iEVE^ WIRES. 



Diameter, 


Weight per 1000'. 


Estimated 
Breaking 


Inches. 








Bare Strand. 


Double Braid 
W. P. 


Triple Braid 
W. P. 


Weight. 


1-2 


520 


616 


677 


8,320 


15-32 


420 


510 


561 


6,720 


7-16 


360 


444 


488 


5,720 


3-8 


290 


362 


398 


4,640 


5-16 


210 


270 


297 


3,360 


9-32 


160 


214 


235 


2,560 


17-64 


120 


171 


188 


1,920 


1-4 


100 


148 


163 


1,600 


7-32 


80 


122 


134 


1,280 


3-16 


60 


96 


105 


960 


11-64 


43 


76 


84 


688 


9-64 


33 


60 


66 


528 


1-8 


24 


48 


53 


384 


3-32 


20 


38 


42 


320 



STRANDED WIRE CARLES. 

(Everett.) 

Ratio of area of copper to area of circular or available space 
copper area 
available area. 



158 



PROPERTIES OF CONDUCTORS. 



If n= number of concentric layers around one central strand, 

3(n 2 + ») + l _, .. 
then (2 7+1? =Batl °- 

The number of wires that will strand will be Zn (n -f- 1) -j- 1. 



Number of Strands. 


copper area 

f. . . = ratio. 

available area 


1 
7 
19 
37 
61 
91 


1.000 
.778 
.760 
.755 
.753 
.752 



Sheathing* Core. — The number, JV, of sheathing wires having a di- 
ameter, d, which will cover a core having a diameter, I), is 



N-. 



D+d 

d ' 



J»ATA OUT CAB1EI. 

Below is given a table showing the actual circular mils, the diameter bare 
inches, and the number and size of strands (wires) generally used in the 
manufacture of cables. 

(General Electric Company.) 









Make up. 


Approx. 




Actual 
Circular 


Diam. 
Bare 






Weight of 


Size of Cable. 






Copper 




Mils. 


Inches. 


No. 
Wires. 


Size wire. 


per 
1000 feet. 


8B.&S. 


18,000 


.147 


7 


16 B. &S. 


57 


6B.&S. 


28,600 


.180 


1 

6 


15 B. &S. 

16 B. W. G. 


85 


5B. &S. 


35,300 


.209 


1 
6 


16 B. W. G. 
15 B. W. G. 


112 


4B.&S. 


44,300 


.234 


1 
6 


15 B. W. G. 
12 B. W. G. 


140 


3B.&S. 


55,900 


.263 


1 
6 


12 B. & S. 
11 B. &S. 


178 


2B. &S. 


70,600 


.295 


6 


11 B. &S. 
10 B. & S. 


224 


1B.&S. 


80,275 


.325 


19 


16 B. W. G. 


255 


OB.&S. 


106,500 


.378 


1 
6 
12 


15 B. W. G. 
12 B. & S. 
15 B. W. G. 


338 


00 B. &S. 


134,200 


.425 


1 
6 
12 


12 B. & S. 

11 B. &S. 

12 B. & S. 


426 


000 B. & S. 


167,500 


.475 


5 
14 


11 B. &S. 
13 B. W. G. 


532 


0000 B. & S. 


216,900 


.524 


1 
6 
13 


10 B. &S. 
12 B. W. G. 
10 B. & S. 


650 



CABLES. 



159 



BATA OH" CABIES — Continued. 





Actual 


Diam. 


Make up. 


Approx. 


Size of Cable. 


Circular 


Bare. 






Weight of 










Mils. 


Inches. 


No. 
Wires. 


Size Wire. 


Copper per 
1000 feet. 


250,000 C. M. 


250,200 


.568 


7 
13 


.117 inch. 
12 B. W. G. 


790 


300,000 C. M. 


304,600 


.637 


37 


11 B. & S. 


949 


350,000 0. M. 


350,400 


.680 


12 
25 


10B.&S. 
13 B. W. G. 


1,092 


400,000 C. M. 


402,600 


.735 


7 
12 
18 


10 B. & S. 
12 B. W. G. 
10 B. & S. 


1,224 


500,000 C. M. 


506,400 


.820 


37 


.117 inch. 


1,550 


600,000 CM. 


601,500 


.900 


37 
24 


10 B. &S. 
13 B. W. G. 


1,874 


750,000 C. M. 


751 ,800 


1.020 


15 

46 


.117 inch. 
12 B. W. G. 


2,331 


800,000 C. M. 


800,600 


1.037 


42 
19 


.117 inch. 
12 B. W. G. 


2,462 


900,000 C. M. 


903,700 


1.096 


12 

49 


8B.&S. 
11 B. W. G. 


2,815 


1,000,000 C. M. 


1,007,000 


1.157 


61 


8B.&S. 


3,138 


1,250,000 CM. 


1,250,600 


1.296 


7 
84 


11 B. W. G. 
.117 inch. 


3,831 


1,500,000 C. M. 


1,512,300 


1.412 


91 


8B. &S. 


4,681 


2,000,000 C M. 


2,001,700 


1.652 


82 
45 


8B. &S. 
11 B. W. G. 


6,237 



UAH STASBARI1 WIIiEi. 
In the following table are given sizes and prices of Navy Standard Wires 
5 per specifications issued by the Navy Department in March, 1897. 



a 




P 


Diameter 


Diameter in 


32ds 


u 


u 

<D <D 


d 


j5 s3 


35 


Inches. 


of an incl 


. 


x' a "S 


03 

2 


O^ 


Over 


Over 


Over 


Over 


Over 


!§s 


C*" 1 
&§ 


< 


%M 


copper. 


Para 
rubber. 


vulc. 
rubber. 


tape. 


braid. 


<^ 


"SS 

3 


4,107 


i 


14 


.06408 


.0953 


7 


9 


11 


56.9 


$60.00 


9,016 


7 


19 


.10767 


.1389 


10 


12 


14 


103 


110.00 


11,368 


7 


18 


.12090 


.1522 


10 


12 


14 


108.5 


110.00 


14,336 


7 


17 


.13578 


.1670 


10 


12 


14 


115.5 


110.00 


18,081 


7 


16 


.15225 


.1837 


11 


13 


15 


140 


130.00 


22,799 


7 


15 


.17121 


.2025 


12 


14 


16 


165J 


150.00 


30,856 


19 


18 


.20150 


.2328 


12 


14 


16 


184 


165.00 


38,912 


19 


17 


.22630 


.2576 


13 


15 


17 


218 


190.00 


49,077 


19 


16 


.25410 


.2854 


14 


16 


18 


260| 


210.00 


60,088 


37 


18 


.28210 


.3134 


15 


17 


19 


314 


260.00 


75,776 


37 


17 


.31682 


.3481 


16 


18 


20 


371 


290.00 


99,064 


61 


18 


.36270 


.3940 


18 


20 


22 


463 


385.00 


124,928 


61 


17 


.40734 


.4386 


19 


21 


23 


557 


415.00, 


157,563 


61 


16 


.45738 


.4885 


20 


22 


24 


647 


460.00 


198,677 


61 


15 


.51363 


.5449 


22 


24 


26 


794 


535.00 


250,527 


61 


14 


.57672 


.6080 


24 


26 


28 


970 


615.00 


296,387 


91 


15 


.62777 


.6590 


26 


28 


30 


1,138 


750.00 


373,737 


91 


14 


.70488 


.7361 


29 


31 


33 


1,420 


900.00 


413,639 


127 


15 


.74191 


.7732 


30 


32 


34 


1,553 


1,000.00 


Double C 


onduc 


tor, Plain, 2-7- 


22 B. &£ 








181.5 


260.00 


Double C 


onduc 
onduc 
, 1-16 


tor, Silk, 2-7-2c 
tor, Diviner Lai 


B. &S. 

np, 2-7-C 








28 

218.3 
29.7 


110 00 


Double C 


OB.&S 






335.00 


Bell Cord 


B. &S 








32 50 

















160 



PROPERTIES OP CONDUCTORS. 



SPECIAL CAKLEfii EOR STREELCAR WIRO«. 

Car wiring cables have a wrapping between the wire and rubber to facili- 
tate stripping for soldering. The 7-14 single braid is adapted for ordinary 
car wiring for two 25 h.p. motors. The triple braid is recommended for taps 
to motors, as it will stand abrasion and is more durable than rubber tubing. 
The 75-25 braided to .500" diameter is standard for field leads of the GE-800 
motor, and fits the rubber bushings in the motor frame. The 49-22 braided 
to .625" diameter is standard for armature leads of the GE-800, and for all 
leads of the GE-1000 motors. These cables are also well adapted for leads 
for suspending arc lamps. 

(General Electric Company.) 





CO 


. 




.-d 


•T3 








'2 a 


"t-m 
55 


r2'£ 
IS r~ 


.3« 


S'cS 
M'ea 




ig; 
■S-s 

Ho 


List price. 


6^ 


Single 


Triple 


fc.S 


W 03 


fl 


^55 


S£ 


braid. 


braid. 


*7 


14 


6 


.192 


.385 


.500 


.062 


$73.50 


$89.00 


49 


23 


6 


.200 


.393 


.500 


.062 


116.50 


131.50 


*75 


25 


6 


.216 


.410 


.500 


.062 


120.00 


135.00 


*7 


12 


4 


.243 


.433 


.553 


.062 


108.50 


127.50 


*49 


22 


4 


.228 


.418 


.625 


.062 


139.50 


160.00 



* Carried in stock. 



ITAKDARD RUBBER COVER KB WHITE CORE 
WIRES ABfD CARIES. 

(Made by General Electric Company.) 

Rubber covered wires and cables are insulated with two or more coats of 
rubber, the inner coat in all cases being free from sulphur or other sub- 
stance liable to corrode the copper, the best grade of fine Para being em- 
ployed. All conductors are heavily and evenly tinned. 

Five distinct finishes can be furnished as follows: — White or black braid, 
plain lead jacket, lead jacket protected by a double wrap of asphalted jute, 
lead jacket armored with a special steel tape, white armored, for submarine 
use. 

For use in conduits the plain lead covering is recommended, or if corro- 
sion is especially to be feared, the lead and asphalt. For use where no con- 
duit is available, the band steel armored cable is best, as it combines 
moderate flexibility with great mechanical strength, enabling it to resist 
treatment which would destroy an unarmored cable. 

In addition to the ordinary galvanometer tests, wires and cables are 
tested with an alternating current (as specified in table) before shipping. 
Are also prepared to quote promptly on wire armored cables for subaqueous 
circuits, but as the conditions and requirements of the weight of armor 
vary greatly, do not list them. Inquiries for quotations on these cables 
should state the length and size of cable, depth of water, character of bot- 
tom and current, in order that a proper weight of armor may be selected. 

The tables following give list prices, dimensions, insulation resistance per 
mile, test pressure, and break-down pressure on all sizes of wires and cables 
in ordinary use. For underground and submarine work it is recommended 
that cables be not worked at more than one-half the pressure with which 
they are tested. If wires or cables are run on insulators in dry places they 
may be safely worked at test pressure. 

Cables will be leaded according to the table given below, unless otherwise 
specified. Cables with any thickness of lead required can be supplied. 
Cables up to \" diameter over insulation, lead g 3 s " thick. 

\ir tr. s// diameter over insulation, lead A" thick. 

" 3 3// « 

ft (( «» 1// « 



over f 



to 

to l-y 

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162 



PROPERTIES OF CONDUCTORS. 



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164 



PROPERTIES OF CONDUCTORS. 



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SPECIAL FINISHES. 



165 



Below is a table of prices at which special finishes for any of the fore- 
going wires and cables can be furnished. 

C. L. Plain lead cover over the rubber. 

C. L. A. Lead cover with jute and asphalt over the lead. 

C. L. A. I. Lead cover, jute and asphalt and band iron armored. 

To obtain the price of the cable desired, add to the list price of the rubber 
covered cable braided, the list price of the finish desired for the diameter 
nearest to that of the braided cable. 

A cable having a lead cover, jute and asphalt over the lead, and wire 
armored (C. L. A. W.), in addition to the above special finishes can also be 
furnished. Prices on application. 

To obtain approximate weight of cable having special finish, add to the 
weight of the cable the weight of the special finish as given below. 



SPECIAL FIA1MHFA 

(General Electric Company.) 



Diameter 


C 


. L. 


C. 


L. A. 


C. L 


. A. I. 


of 

Braided 

Cable. 

Inches. 


Approx. 
Weight 

per 
1000 feet. 


List price 

per 
1000 feet. 


Approx. 
Weight 

per 
1000 feet. 


List price 

per 
1000 feet. 


Approx. 
Weight 

per 
1000 feet. 


List price 

per 
1000 feet. 


.200 


157 


$30.00 


252 


$60.00 




» • • 


.225 


170 


31.50 


268 


62.50 






.250 


191 


34.00 


297 


66.50 






.275 


214 


37.00 


327 


70.50 






.300 


227 


38.50 


345 


73.00 






.325 


345 


53.00 


475 


89.50 






.350 


376 


57.00 


514 


94.50 


1,131 


$193.50 


.375 


391 


59.00 


534 


97.00 


1,162 


197.50 


.400 


424 


63.00 


574 


102.00 


1,229 


206.50 


.425 


438 


65.00 


590 


105.50 


1,254 


212.00 


.450 


473 


69.00 


634 


111.50 


1,325 


222.00 


.475 


498 


72.50 


665 


115.00 


1,370 


227.50 


.500 


519 


75.00 


691 


117,00 


1,417 


230.00 


.550 


567 


79.00 


751 


125.00 


1,506 


241.50 


.600 


620 


85.50 


816 


133.00 


1,616 


255.50 


.650 


656 


90.00 


864 


139.00 


1,901 


294.00 


.700 


1,118 


144.50 


1,352 


199.00 


2,498 


369.00 


.750 


1,194 


153.00 


1,442 


209.50 


2,632 


384.50 


.800 


1,194 


153.00 


1,442 


209.50 


2,632 


384.50 



1G6 PROPERTIES OF CONDUCTORS. 

SJPECIAE FlUfliHES- Continued. 



Diameter 


C 

Approx. 
Weight 

per 
1000 feet. 


. L. 

List price 

per 

1000 feet. 


C. 


L. A. 


C. L 


. A. I. 


of 

Braided 

Cable. 

Inches. 


Approx. 
Weight 

per 
1000 feet. 


List price 

per 
1000 feet. 


Approx. 
Weight 

per 
1000 feet. 


List price 

per 
1000 feet. 


.850 


1,258 


160.50 


1,516 


218.00 


2,742 


398.50 


.900 


1,317 


167.00 


1,583 


226.50 


2,847 


411.50 


.950 


1,423 


179.50 


1,707 


241.50 


3,022 


433.50 


1.000 


1,482 


186.50 


1,773 


249.00 


3,132 


447.00 


1.05 


1,556 


190.00 


1,859 


257.50 


3,263 


461.00 


1.1 


1,631 


201.00 


1,946 


267.50 


3,397 


477.00 


1.15 


1,705 


210.00 


2,030 


277.50 


3,820 


533.50 


1.2 


1,795 


220.00 


2,131 


291.50 


3,987 


559.00 


1.25 


1,854 


225.50 


2,201 


298.50 


4,098 


572.50 


1.3 


1,959 


237.50 


2,322 


313.00 


4,294 


595.50 


1.35 


2,018 


240.00 


2,393 


317.50 


4,409 


607.00 


1.4 


2,851 


330.00 


3,257 


415.00 


5,419 


724.00 


1.45 


2,989 


348.00 


3,410 


432.50 


5,639 


750.50 


1.5 


3,008 


350.00 


3,432 


434.50 


5,681 


755.00 


1.6 


3,362 


378.00 


3,717 


470.00 


6,097 


810.00 


1.7 


3,400 


392.50 


3,872 


488.00 


6,335 


827.50 


1.8 


3,615 


416.50 


4,113 


515.50 


6,694 


882.00 


1.9 


3,792 


436.00 


4,309 


538.00 


6,987 


905.50 


2 


3,988 


457.50 


4,529 


563.00 


7,315 


945.00 



In leading cables a tape is used over the rubber in place of the regular 
braid. 

For thickness of lead used on above finishes, see page 160. If other thick- 
nesses than these are desired, special prices will be quoted upon application. 

PAPER IX*rH,A r ir*:i» AXl) LEADED wares aid 
CABLES. 

There will be found on the following pages data and prices of a full line 
of paper insulated and lead covered wires and cables. All cables insulated 
with the fibrous covering depend for their successful operation and mainte- 
nance upon the exclusion of moisture by the lead sheath; and this fact 
should constantly be borne in mind in handling this class of cables, conse- 
quently the lead on these cables is extra heavy. The use of jute and asphalt 
covering over the lead is strongly recommended on all this class of cables, 
inasmuch as the life of the cable is absolutely dependent upon that of the 
lead. Paper insulated cables cannot be furnished without the lead covering. 



WIRES AND CABLES. 



167 



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TELEPHONE CABLES. 



169 



TELEPHONE CABLES. 

(By John A. Roebling's Son's Co.) 

Lead-encased for Underground or Aerial Use. 

The insulation of these cables is dry paper. The company manufac- 
tures several styles of 19 B. & S. G., 20 B. & S., G., and 22 B. & S. G., ac- 
cording to the use for which they are intended. The most common size 
is 19 B. & S. G. They also supply terminals and hangers. 

Specifications for Telephone Cables. 

1. Conductors. 
Each conductor shall he .03589 inches in diameter (19 B. & S. G.), and 
have a conductivity of 98 per cent, of that of pure soft copper. 

2. Core. 
The conductor shall he insulated, twisted in pairs the length of the twist 
not to exceed three inches, and formed into a core arranged in reverse 
layers. 

3. Sheath. 
The core shall be enclosed in a pipe composed of lead and tin, the amount 
of the tin shall be not less than 2f$ per cent. The pipe shall be formed 
around the core, and shall be free from holes or other defects, and of uni- 
form thickness and composition. 

4. Electrostatic Capacity. 
The average electrostatic capacity shall not exceed .080 of a microfarad 
per mile, each wire being measured against all the rest, and the sheath 
grounded ; the electrostatic capacity of any wires so measured shall not 
exceed .085 of a microfarad per mile. 

5. Insulation Eesistance. 

Each wire shall show an insulation of not less than 500 megohms per 
mile, at 60° F., when laid, spliced, and connected to terminal ready for use ; 
each wire being measured against all the rest and sheath grounded. 

6. Conductor Resistance. 

Each conductor shall have a resistance of not more than 47 B. A. ohms, 
at 60° F., for each mile of cable, after the cable is laid, and connected to the 
terminals. 

TELEPHONE CABLES. 

By John A. Roebling's Son's Co. 



Number pairs. 


Outside diameters. 
Inches. 


"Weights 1000 feet. 
Pounds. 


1 


f 


214 


2 


302 


3 


h 


515 


4 


& 


629 


6 


s 


747 


6 

7 


8 


877 
912 


10 


13 


1,214 


12 


tt 


1,375 


15 


1 


1,566 



170 PROPERTIES OF CONDUCTORS. 

TELEPHOHTE CABLE!- Continued. 



Number Pairs. 


Outside Diameters. 
Inches. 


Weights 1000 feet. 
Pounds. 


18 
20 
25 
30 
35 


1ft 

If 

1ft 

x 2 


1,758 
1,940 
2,332 

2,748 
2,985 


40 
45 
50 
55 
60 


1ft 
If 
If 
lit 

1| 


3,176 
3,365 
3,678 
3,867 
4,055 


65 
70 
80 
90 
100 


2* 

2f 


4,241 
4,430 
4,804 
5,180 
5,505 



TELEGRAPH CABLES. 

By John A. Roebling's Son's Co. 
Lead-encased for Underground Use. 

These cables are made of either rubber, cotton, or paper insulation. The 
sizes and weights are approximately correct for rubber and cotton insula- 
tion. Both sizes and weights are slightly reduced for paper insulation. In 
all cases the cables are lead-encased. 

Specifications for Telegraph Cables. 

1. Conductors. 

Each conductor shall be .064 inches in diameter (14 B. & S. G.), and have 
a conductivity of 98 per cent of that of pure copper. 

2. Core. 

The conductors shall be insulated to ^ with cotton, and formed into a 
core arranged in reverse layers. This core shall be dried, and saturated 
with approved insulating compound. 

3. Sheath. 

The core shall be enclosed in a pipe composed of lead and tin. The 
amount of tin shall not be less than 2.9 per cent. The pipe shall be formed 
around the core, and shall be free from holes or other defects, and of uni- 
form thickness and composition. 

4. Insulation Resistance. 

The wire shall show an insulation of not less than 300 megohms per mile, 
at 60° F., when laid, spliced, and connected to terminals ready for use, each 
wire being measured against all the rest and the sheath grounded. 

5. Conductor Resistance. 

Each conductor shall have a resistance of not more than 28 International 
ohms, at 60° F., for each mile of cable, after the cable is laid, and connected 
up to the terminals. 



Ttfl.KGRAPH CABLES. 



171 



TELEGRAPH CARLEi. 

By John A. Roebling's Son's Co. 





14 B. 


& S. G. 


16 B. 


&S.G. 


18 B. 


&S. G. 


GO 

u 

o 


Insulated to £%. 


Insulated to 3 5 5 . 


Insulated to ^. 




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II 


j 


I 


308 


299 


3 


291 


2 


A 


438 


A 


421 


13 


356 


3 




573 


i 


546 


7 


421 


4 


f 


810 


A 


670 


IS 

F 


486 


5 


1 


972 


1 


793 


551 


6 


13 


1,132 




946 


17 
32 


616 


7 


B 


1,295 




965 


A 


681 


10 


» 


1,512 


If 


1,155 


i 


820 


12 


*A 


1,873 


5 


1,327 


978 


15 


ll 3 F 


2,263 


15 
16 


1,518 


u 


1,148 


18 


li 


2,523 


1A 


1,880 




1,318 


20 


1A 


2,756 


i* 


2,076 


ii 


1,477 


25 


1A 


3,250 


1A 


2,496 ' 


i 


1,690 


30 


ll 9 6 


3,515 


if 


2,768 


1A 


1,903 


35 


1« 


3,910 


1A 


3,040 


1A 


2,116 


40 


If 


4,175 


H 


3,312 


U 


2,330 


45 


1« 


4,441 


*A 


3,533 


1A 


2,471 


50 


lit 


4,835 


if ' 


3,755 


1A 


2,628 


55 


2 


5,100 


ill 


3,978 


if 


2,866 


60 


2A 


5,365 


if 


4,200 


1A 


3,104 


65 


21 


5,631 


m 


4,422 


m 


3,245 


70 


2ft 


5,897 


ii 


4,644 


n 


3,402 


80 


2A 


6,408 


2 


5,087 


it 


3,798 i 


90 


2A 


6,916 


2A 


5,402 


m 


4,027 


100 


2i 9 s 


7,375 


2| 


5,720 


n 


4,275 



AERIAL CABLES. 
By John A. Roebling's Son's Co. 

These cables are made from double-coated rubber wire, taped. After 
standing, the cable is double-taped, aud covered with tarred jute, over which 
is placed a braid of heavy cotton saturated with weatherproof compound. 
This outside covering protects the rubber from the action of the air and 
from mechanical injury. The separate wires are tested in water, and no 
wire is used which will not fully meet a water test. Tbe result is a cable 
which will work under water as well as on a pole line, if there is no danger 
of mechanical injury. The ordinary size for telegraphic work is 14 B. & S. s 
insulated to 3 \. A trace wire can be placed in each layer, if desired. 



1<*2 PROPKRTIES OF CONDUCTORS. 

Specifications for 14 I*. & S. Aerial Cable. 

1. Conductors. 

Each conductor shall be .064 inches in diameter (14 B. &S. G.), and have 
a conductivity of 98 per cent of that of pure copper. 

2. Coke. 

The conductors shall he insulated to 3 6 2 with rubber and tape, and formed 
into a core arranged in reverse layers. 

3. Protective Covering. 

The core shall be covered with two wraps of friction tape and one wrap of 
tarred jute. Over this there shall be a braid saturated with weatherproof 
compound. 

4. Insulation Resistance. 

Each wire shall show an insulation resistance of not less than 300 meg- 
ohms per mile, at 60° F., after being immersed in water 24 hours. This test 
shall be made on the core after all the conductors are laid up, but before 
the outside coverings are put on. 

5. Conductor Resistance. 

Each conductor shall have a resistance of not more than 28 international 
ohms, at 60° F., for each mile of cable. 



AERIAI CABLE§. 

By John A. Roebling's Son's Co. 

Rubber insulation. 





14 B. & S. G. 


16 B. &S. G. 


18 B. & S. G. 


03 


Insulated to 3 V 


Insulated to &. 


Insulated to 3 4 5 . 




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102 


§ 


92 


§ 


82 


3 


149 


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126 


if 


104 


4 


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183 


i 


155 


i 7 s 


127 


5 


226 


I 


193 


1 


151 


6 


1 


260 


H 


222 


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175 


7 


11 


297 


1 


251 


§ 


200 


10 


\% 


401 


1 


335 


tt 


256 


12 


l 


465 


11 


393 


1 


296 


15 


is 


563 


1 


468 




355 


18 


lT 3 5 


651 


ift 


541 


1 


413 



AERIAL CABLES. 



173 



AERIAL CABIEi- Continued. 





14 B. & S. G. 


16 B. & S. G. 


18 B. &S. G. 


CO 

o 


Insulated to 5 e 5 . 


Insulated to 3 S 2 . 


Insulated to g \ . 












m 






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20 


ii 


714 


ii 


593 


29 


452 


25 


i§ 


863 


1t 3 b 


708 


it 


541 


30 


i& 


1,008 


1J 


824 


l 


633 


35 


i* 


1,147 


ll 5 5 


938 


Ws 


723 


40 


ii 9 5 


1,268 


If 


1,053 


14 


813 


45 


it 


1,431 


n 


1,182 


h% 


903 


50 


ii 


1,577 


if 


1,311 


U 


994 



SUBMARINE CABIEi. 

By John A. Roebling's Son's Co. 



CO 




Armor 


wires. 


Total weights. Pounds. 


u O 


Outside 
diameters. 










i° P 














Number 
of wires. 


Numbers, 
B. W. G. 


1,000 feet. 


Mile. 


i 


£ 


12 


8 


1,250 


6,600 


2 


1 


15 


8 


1,722 


9,092 


3 


1* 


14 


6 


2,363 


12,477 


4 


li 5 S 


16 


6 


2,794 


14,752 


5 


1ft 


16 


6 


2,968 


15,671 


6 


1* 


16 


4 


3,822 


20,180 


7 


li 


16 


4 


3,972 


20,972 


10 


1| 


18 


3 


5,404 


28,533 



The core consists of 7 x 22 B. & S. tinned copper wires, insulated with 
rubber to 3 8 2 of an inch, laid up with proper jute bedding. 

Telegraph cables can be supplied with gutta-percha insulation. This is 
the best insulation for submarine work, and its reliability and durability 
more than make up the difference in cost between it and any other insula- 
tion. 



174 PROPERTIES OF CONDUCTORS. 



AirMMfUItt. 

(From paper by Alfred E. Hunt, S. B., and book published by the Pitts- 
burg Reduction Company.) 

Specific gravity 2.68 

Cubic foot weighs, cast „ . . 159.6 lbs. 

Cubic foot weighs, rolled 167.1 " 

Cubic inch weighs, cast .0924 " 

Cubic inch weighs, rolled .0967 " 

Tensile strength in pure soft Avire, per square inch . . 26,000 
Tensile strength in pure hard-drawn rods, per square inch, 40,000 
Conductivity as related to 100% cond. copper: 

99J%pnre 63.09% 

99% pure 62.17% 

98% pure 56.17% 

Approximate weight per mile of aluminum wire = .004817 X cir. mils. 

Aluminum for Electrical Conductors. 

(From paper by Alfred E. Hunt, S. B.) 

8 98 

1. Any given volume of copper is-: — or 3.332 times heavier than an 
equal volume of aluminum. 2.68 

2. The equivalent price of fourteen cents per pound for copper for any 
length of any equivalent section of aluminum wire or bar would be 14 cents 
times the factor 3.332, or 46.65 cents per pound. That is, one thousand feet 
of wire of, say, one-tenth inch diameter, would cost equally as much if 
bought of copper at 14 cents per pound or aluminum at 46.65 cents per 
pound. Aluminum, therefore, at 29 cents per pound is only 62% of the cost 
of copper at 14 cents per pound, section for section. 

3. Reckoning the copper conductor to have its maximum of 100 per cent 
conductivity, and the aluminum to have a conductivity of 63 per cent (which 
the Pittsburg Reduction Company are ready to guarantee for their special 
pure aluminum metal for electrical conductors), then for an equivalent 
electrical conductivity a given section of copper that can be placed at 100 
should be increased in area in round numbers to 160 to give an equal con- 
ductivity. 

4. Due to their relative specific gravities, the weight of the given equal 
length of the aluminum conductor with 160 sectional area will be only forty- 
eight per cent of the weight of the copper conductor with sectional area of 
100, having the same electrical conductivity. 

100 y 8.93 = 893, weight of the copper. 

160 x 2.68 z=428.8, weight of the aluminum. 

-i§5 a = 48 per cent. 

5. As to their relative cost for electrical conductors of equal conductiv- 
ity, aluminum at twenty-nine cents per pound is the most economical con- 
ductor, as compared with copper at fourteen cents per pound. 

Taking as an illustration, an aluminum conductor to replace a copper 
wire of No. 10 B. & S. gauge (about one-tenth of an inch diameter), the 
aluminum wire of equal, in fact somewhat superior, electrical conductivity 
would be of No. 8 B. & S. gauge ( slightly over one-eighth of an inch 
diameter). 

The weight of a mile of No. 10 copper wire is 162.32 pounds ; and its cost 
at 14 cents per pound would be equal to $22.72. 

The weight of a mile of No. 8 aluminum wire would be 79.46 pounds, and 
at twenty-nine cents per pound would cost $23.04. 

Forty-eight per cent of the weight of No. 10 copper wire, which will 
give equal electrical conductivity in aluminum wire, would only weigh 
77.91 pounds; so that, more accurately, $22.59 would be the cost of a mile 
of aluminum wire at 29 cents per pound to replace a mile of No. 10 copper 
wire at 14 cents per pound, costing $22.72. 

6. The Continental requirements in tensile strength for soft copper 
wire, rods, and bars used as electrical conductors is twenty-two kilograms 
per square millimeter ; the English requirement being similarly fourteen 
tons per square inch; and our American requirement is about its equivalent 
of 32,000 pounds per square inch. 



ALUMINUM. 



175 















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176 



PROPERTIES OF CONDUCTORS. 



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ALUMINUM WIRE. 



177 



TABLE OF MESISTA1VCES OJF PUJRK AI/U1»II]¥U]»I 

WIBI.* 

(Pittsburg Reduction Company.) 

Pure aluminum weighs 167.111 pounds to the cubic foot. The conductivity 
of pure aluminum is 60% Of the conductivity of pure copper. 







Resistance at 75% F. 




Am. Gauge, 
B. &S. No. 










R 

Ohms 1,000 ft. 










Ohms per mile. 


Feet per ohm. 


Ohms per lb. 


0000 


.08177 


.43172 


12,229.8 


.00042714 


000 


.10310 


.54440 


9,699.0 


.00067022 


00 


.13001 


.68645 


7,692.0 


.00108116 





.16385 


.86515 


6,245.4 


.0016739 


1 


.20672 


1.09150 


4,637.35 


.0027272 


2 


.26077 


1.37637 


3,836.22 


.0043441 


3 


.32872 


1.7357 


3,036.12 


.0069057 


4 


.41448 


2.1885 


2.412.60 


.0109773 


5 


.52268 


2.7597 


1,913.22 


.017456 


6 


.65910 


3.4802 


1,517.22 


.027758 


7 


.83118 


4.3885 


1,203.12 


.044138 


8 


1.06802 


5.5355 


964.18 


.070179 


9 


1.32135 


6.9767 


756.78 


.111561 


10 


1.66667 


8.8000 


600.00 


.17467 


11 


2.1012 


11.0947 


475.908 


.28211 


12 


2.6497 


13.9900 


377.412 


.44856 


13 


3.3412 


17.642 


299.298 


.71478 


14 


4.3180 


22.800 


231.582 


1.16225 


15 


5.1917 


27.462 


192.612 


1.7600 


16 


6.6985 


35.368 


149.286 


2.8667 


17 


8.4472 


44.602 


118.380 


4.5588 


18 


10.6518 


56.242 


93.882 


7.2490 


19 


13.8148 


72.942 


72.384 


12.1916 


20 


16.938 


89.430 


59.0406 


18.328 


21 


21.358 


112.767 


46.8222 


29.142 


22 


26.920 


142.138 


37.1466 


46.316 


23 


33.962 


179.32 


29.4522 


73.686 


24 


42.825 


226.12 


23.3508 


117.170 


25 


54.000 


285.12 


18.5184 


186.28 


26 


68.113 


359.65 


14.6814 


296.32 


27 


85.865 


453.37 


11.6460 


485.56 


28 


108.277 


571.70 


9.2358 


749.02 


29 


136.535 


720.90 


7.3242 


1,190.97 


30 


172.17 


908.98 


5.8087 


1,893.9 


31 


212.12 


1,119.98 


4.7144 


2,941.5 


32 


273.97 


1,445.45 


3.6528 


4,788.9 


33 


345.13 


1,822.3 


2.8974 


7,610.7 


34 


435.38 


2,298.8 


2.2969 


12,109.4 


35 


548.92 


2,898.2 


1 .8218 


19,251. 


36 


692.07 


3,654.2 


1.4449 


30,600. 


37 


872.93 


4,609.2 


1.1456 


48,661. 


38 


1,100.62 


5,811.2 


.9086 


76.658. 


39 


1,387.47 


7,325.8 


.7207 


121,881. 


40 


1,749.50 


9,236.8 


.5716 


193,835. 



* Calculated on the basis of Dr. Matthiessen's standard, viz. : 1 mile of 
pure copper wire of T a g inch diameter equals 13.59 ohms at 15.5° C. or 
59.9° F. 



178 



PROPERTIES OP CONDUCTORS. 



Care in Erecting- Aluminum Lines. 

The fact that the wire will permanently elongate if seriously strained, 
makes it necessary to use the utmost care in the erection of lines, and also 
the known high coefficient of expansion with temperature changes taken in 
conjunction with this property renders care in line stringing especially im- 
portant and difficult. 

The following tahle has been gotten out by the Pittsburg Reduction 
Company, after exhaustive experiments. 



Tal»le of Deflections and Tensions for Aluminum Wire. 

X=z Deflection in inches at center of span. 

S = Factor, which multiply by weight of foot of wire to obtain tension. 

Maximum Load = 15,000 per square inch. 

(Trans. A. I. E. E.) 





< = — 


20° 


— 10° 


0° 


10° 


20° 


30° 


Span. 


S 


X 


s 


X 


s 


A 


s 


X 


S 


X 


S 


X 


80 


12940 


! 


1600 


5| 


1176 


S£ 


901 


10 


833 


ni 


781 


m 


100 


12940 


i| 


2083 


71 


1470 


10J 


1202 


12i 


1042 


14| 


933 


16 


120 


12940 


if 


2500 


8f 


1768 


121 


1400 


15£ 


1251 


17* 


1120 


19i 


150 


12940 


2f 


3038 


Hi 


2540 


"i 


1788 


m 


1552 


21 f 


1390 


24 


175 


12940 


3£ 


3643 


12f 


2576 


17| 


2104 


21| 


1822 


25} 


1630 


28} 


200 


12940 


4f 


4206 


14! 


2947 


20f 


2403 


24£ 


2084 


28| 


1930 


31i 





/ = 40° 


50° 


69° 


70° 


80° 


90° 


Span. 


S 


X 


S 


X 


S 


X 


S* 


X 


S 


X 


S 


X 


80 


680 


14i 


630 


15J 


589 


16| 


555 


m 


527 


18} 


502 


19 J 


100 


869 


171 


768 


19 


735 


2Q| 


695 


21* 


658 


22J 


628 


23| 


120 


1022 


21| 


946 


22| 


885 


242 


835 


25| 


792 


27} 


755 


28| 


150 


1265 


26| 


1177 


28f 


1060 


30f 


1039 


32A 


987 


34} 


941 


353 


175 


1488 


30| 


1377 


33| 


1279 


35^ 


1215 


37| 


1152 


39| 


1099 41;} 


200 


1672 


35$ 


1574 


38} 


1473 


40| 


1393 


43 


1316 


45£ 


1256 


473 



ALUMINUM WIRE. 



179 



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180 



PROPERTIES OF CONDUCTORS. 



Aluminum wire, rods, and bars will be furnished of 63 per cent electrical 
conductivity, which will have an equal tensile strength per unit of area 
with the copper, and therefore with the electrical conductivity equivalent 
of 48 per cent of the weight of the copper and sectional area of 160 against 
the area of the copper section 100, the tensile strength of the aluminum con- 
ductors will be as 100 for the copper is to 160 for the aluminum. This 
would mean, if a square inch of copper conductor was used of, say, 32,000 
pounds per square inch tensile strength, the equal conductivity area of 1.6 
inches of aluminum would have a tensile strength of 51,200 pounds. 

It has already been determined that with aerial lines, the snow and ice 
load is practically as heavy on lengths of small wire as upon larger sections, 
so that no objection upon this score can probably be found to the use of the 
larger sections of aluminum wire. 

Both on account of having only 48 per cent of the weight, and on account 
of having about 60 per cent more strength, the aluminum conductor could 
be used in much longer spans between supports, and the number of expen- 
sive poles and insulators can be materially diminished. 



GffiRJI A'X SIEVER. 

German silver is most extensively used for resistances. 

A cubic foot weighs about 530 lbs.; specific gravity, 8.5. 
Composition : copper, 4 parts ; zinc, 1 part ; nickel, different per 

centages. 
Specific resistance, 20.9, or 13 times copper. 
1 mil-foot, resistance 125.91 ohms. 
Temperature variation, for 1° C. .044% from to 100° C. 



RESISTANCES OF OERMAUT 8ILTEH WIRE. 

(American Gauge.) 





18% 


30% 


Size. 


Ohms per 


Ohms per 


Ohms per 


Ohms per 
pound. 


1,000 feet. 


pound. 


1,000 feet. 


No. 8 


11.772 


.23598 


17.658 


.35397 


9 


11.832 


.37494 


17.7*8 


.56241 


10 


18.72 


.59652 


28.08 


.89478 


11 


23.598 


.94842 


35.397 


1.42263 


12 


29.754 


1.50786 


44.631 


2.26179 


13 


37.512 


2.39778 


56.268 


3.59667 


14 


47.304 


3.8124 


70.956 


5.7186 


15 


59.652 


6.0624 


89.478 


9.0936 


16 


75.222 


9.639 


112.833 


14.458 


17 


94.842 


15.327 


142.263 


22.990 


18 


119.61 


24.3702 


179.41 


36.5553 


19 


155.106 


40.9896 


232.659 


61.4844 


20 


190.188 


61.614 


285.282 


92.421 


21 


239.814 


97.974 


359.721 


146.961 


22 


302.382 


155.772 


453.573 


233.658 


23 


381.33 


247.734 


571.99 


371.601 


24 


480.834 


393.93 


721.251 


590.89 


25 


606.312 


626.31 


909.468 


939.46 


26 


764.586 


995.958 


1,146.879 


1,493.937 


27 


964.134 


1,583.622 


1,446.201 


2,375.433 


28 


1,215.756 


2,518.075 


1,823.634 


3,777.112 



GERMAN SILVER WIRES. 



181 



RESISTANCES OF GERMAN SILVER WIKE- 

Continued. 





18% 


30% 


Size. 


Ohms per 


Ohms per 


Ohms per 


Ohms per 


1,000 feet. 


pound. 


1,000 feet. 


pound. 


No. 29 


1,533.06 


4,004.082 


2,299.59 


6,006.123 


30 


1,9,33.038 


6,368.356 


2,899.557 


9,552.534 


31 


2,437.236 


10,119.978 


3,655.854 


15,179.967 


32 


3,073.77 


16,096.356 


4,610.65 


24,144.534 


33 


3,875.616 


25.589.628 


5,813.424 


38,384.442 


34 


4,888.494 


40,712.76 


7.332.741 


61,069.14 


35 


6,163.974 


64,729.87 


9,245.961 


97,094.80 


36 


7,770.816 


102,876.482 


11,656.224 


154,314.723 


37 


9,797.166 


163,524.78 


14,695.749 


245,287.17 


38 


12,357.198 


257,764.68 


18,535,797 


386,647.02 


39 


15,570.828 


409,546.8 


23,356.242 


614,320.2 


40 


19,653.57 


652,024.62 


29,480.35 


978,036.93 



REIATI1E RESISTANCES OF METAI AIIOIS. 

Copper 1. 

Platinum silver — 

lilt" 11111 ' IK} 20.5 approximately. 

German silver — 

Copper, 4 parts ) 

Nickel, 2 parts > 12.8 approximately. 

Zinc, 1 part J 

Gold-Silver — 

g&, V&] H.6 approximately. 

Platinoid — 

German Silver, with 1 — 2 of Tungsten . . . 19.2 approximately. 



REIATIVE CONDUCTIVITIES OE METAES AND 

ALLOYH. 

(Weiller.) 

1. Pure silver 100 

2. Pure copper < 100 

3. Refined and crystallized copper 99.9 

4. Telegraphic silicious bronze 98 ^ 

5. Alloy of copper and silver (50 per cent) 86.65 

6. Pure gold ■> • 78 

7. Silicide of copper, with 4 per cent of silicium 75 

8. Silicide of copper, with 12 per cent of silicium 54.7 

9. Aluminum, 99£ 63.09 

10. Tin with 12 per cent of sodium 46.9 

11. Telephonic silicious bronze 35 

12. Copper with 10 per cent of lead 30 

13. Pure zinc ,• • • 29 - 9 

14. Telephonic phosphor-bronze 29 

15. Silicious brass with 25 per cent of zinc 26.49 

16. Brass with 35 per cent of zinc 21.5 

17. Phosphor tin 17.7 



182 



PROPERTIES OF CONDUCTORS. 



Alloy of gold and silver (50 per cent) 16. 

Swedish, iron 16 

Pure Banca tin ! . , 15. 

Antimonial copper 12. 

Aluminum bronze (10 per cent) 12. 

Siemens's steel , 12 

Pure platinum ................... 10. 

Copper with 10 per cent of nickel ........... 10. 

Cadmium amalgam (15 per cent) ............ 10. 

Dronier mercurial bronze 10. 

Arsenical copper (10 per cent) 9. 

Pure lead 8. 

Bronze with 20 per cent of tin ............ . 8. 

Pure nickel 7. 

Phosphor-bronze with 10 per cent of tin ........ . 6. 

Phosphor-copper with 9 per cent of phosphorus 4. 

Antimony 3. 



TEKPERATIJItE OF CONDUCTORS WITH 
COJEJFJFIC*JEJ¥TS. 



(From Kempe.) 

For metals the resistance increases as the temperature increases. The 
formula which represents the effect of temperature may be written 

lit = llo (1 + oo* + &P) 

where lit is the resistance at the final temperature, Ji is the resistance at 
•the standard temperature, t is the increase in temperature, and oo and (& 
are coefficients. 
For most purposes the following approximate formula may be used : 

Rt = JRo (1 -f oo t). 
The value of oo for use in the approximate formula is given in the follow- 
ing table, ooc being the value per centigrade degree, and oo/per Fahrenheit 
degree. 



Metal. 


0Oc 


CO/ 


Silver 


0.00377 


0.00210 


Copper 


0.00388 


0.00215 


Gold 


0.00365 


0.00203 


Aluminum 


0.00390 


0.00217 


Platinum 


0.00247 


0.00137 


Iron 


0.00453 


0.00252 


Tin 


0.00365 


0.00203 


Lead 


0.00385 


0.00214 


Mercury 


0.00088 


0.00049 


Alloy, 2Pt + l Ag . . 


0.00022 to 0.00031 


0.00012 to 0.00017 


2 Au -f 1 Ag . 


0.00065 


0.00036 


8 Pt + 1 Ir . . 


0.0013 


0.00072 


German Silver . . . 


0.00028 to 0.00044 


0.00016 to 0.00024 



TEMPERATURE. 



183 



Dividing- Coefficients for Correcting- the observed Resist- 
ance of Gutta-Percha at any Temperature to ?5° V. 



Temp. 
F.° 


Coeff. 


Temp. 
F. 


Coeff. 


Temp. 
F.° 


Coeff. 


Temp. 
F.° 


Coeff. 


90 


.3197 


77.5 


.8269 


65 


2.139 


52.5 


5.533 


89.5 


.3320 


77 


.8589 


64.5 


2.222 


52 


5.748 


89 


.3449 


76.5 


.8922 


64 


2.308 


51.5 


5.970 


88.5 


.3583 


76 


.9267 


63.5 


2.397 


51 


6.202 


88 


.3722 


75.5 


.9627 


63 


2.490 


50.5 


6.442 


87.5 


.3866 


75 


1.000 


62.5 


2.587 


50 


6.692 


87 


.4016 


74.5 


1.039 


62 


2.687 


49.5 


6.951 


86.5 


.4171 


74 


1.079 


61.5 


2.792 


49 


7.220 


86 


.4343 


73.5 


1.121 


61 


2.899 


48.5 


7.500 


85.5 


.4501 


73 


1.164 


60.5 


3.012 


48 


7.791 


85 


.4675 


72.5 


1.209 


60 


3.128 


47.5 


8.093 


84.5 


.4856 


72 


1.256 


59.5 


3.250 


47 


8.406 


84 


.5044 


71.5 


1.305 


59 


3.376 


46.5 


8.732 


83.5 


.5240 


71 


1.355 


58.5 


3.506 


46 


9.070 


83 


.5443 


70.5 


1.408 


58 


3.642 


45.5 


9.422 


82.5 


.5654 


70 


1.463 


57.5 


3.783 


45 


9.787 


82 


.5873 


69.5 


1.519 


57 


3.930 


44.5 


10.17 


81.5 


.6100 


69 


1.578 


56.5 


4.082 


44 


10.56 


81 


.6337 


68.5 


1.639 


56 


4.240 


43.5 


10.97 


80.5 


.6582 


68 


1.703 


55.5 


4.405 


43 


11.39 


80 


.6837 


67.5 


1.769 


55 


4.575 


42.5 


11.84 


79.5 


.7102 


67 


1.837 


54.5 


4.753 


42 


12.29 


79 


.7378 


66.5 


1.908 


54 


4.937 


41.5 


12.77 


78.5 


.7663 


66 


1.982 


53.5 


5.128 


41 


13.27 


78 


.7960 


65.5 


2.059 


53 


5.327 


40.5 


13.78 



Example : The insulation resistance at 62° F. of a wire insulated with 



Gutta-percha is 500 meghoms 
Resistance : 



what is the resistance at 75° F. ? 
500 -f- 2.687 = 186.1 megohms. 



Dividing Coefficients for Correcting tiae observed Resist- 
ance of Hooper's India -Rubber at any Temperature 

to »5° JF. 



Temp. 

F.° 


Coeff. 


Temp. 
F.= 


Coeff. 


Temp. 

F.° 


Coeff. 


Temp. 

F.° 


Coeff. 


90 


.680 


80.5 


.868 


71 


1.108 


61.5 


1.414 


89.5 


.691 


80 


.880 


70.5 


1.122 


61 


1.433 


89 


.698 


79.5 


.891 


70 


1.137 


60.5 


1.451 


88.5 


.708 


79 


.902 


69.5 


1.152 


60 


1.470 


. 88 


.716 


78.5 


.914 


69 


1.167 


59.5 


1.489 


87.5 


.726 


78 


.926 


68.5 


1.182 


59 


1.508 


87 


.735 


77.5 


.938 


68 


1.197 


58.5 


1.527 


86.5 


.745 


77 


.950 


67.5 


1.212 


58 


1.547 


86 


.754 


76.5 


.963 


67 


1.228 


57.5 


1.567 


85.5 


.764 


76 


.975 


66.5 


1.244 


57 


1.587 


85 


-.774 


75.5 


.987 


66 


1.260 


56.5 


1.608 


84.5 


.784 


75 


1.000 


65.5 


1.276 


56 


1.629 


84 


.794 


74.5 


1.013 


65 


1.293 


55.5 


1.650 


83.5 


.804 


74 


1.026 


64.5 


1.309 


55 


1.671 


83 


.814 


73.5 


1.039 


64 


1.326 


54.5 


1.693 


82.5 


.825 


73 


1.053 


63.5 


1.343 


54 


1.715 


82 


.836 


72.5 


1.008 


63 


1.361 


53.5 


1.737 


81.5 


.846 


72 


1.080 


62.5 


1.378 


53 


1.759 


81 


.857 


71.5 


1.094 


62 


1.396 


52.5 


1.782 



184 



PROPERTIES OF CONDUCTORS. 



Dividing- Coefficients — Continued. 



Temp. 

F.° 


Coeff. 


Temp. 

F.° 


Coeff. 


Temp. 

F.° 


Coeff. 


Temp. 

F.° 


Coeff. 


52 


1.805 


49 


1.949 


46 


2.106 


43 


2.274 


51.5 


1.828 


48.5 


1.975 


45.5 


2.133 


42.5 


2.303 


51 


1.852 


48 


2.000 


45 


2.160 


42 


2.333 


50.5 


1.876 


47.5 


2.026 


44.5 


2.188 


41.5 


2.363 


50 


1.900 


47 


2.052 


44 


2.216 


41 


2.394 


49.5 


1.925 


46.5 


2.079 


43.5 


2.245 


40.5 


2.424 



TI van Temperature. 

A piece of wire or cable whose length is I, and temperature £°, when con- 
nected to another wire or cable whose length is l ly and temperature < 1 °, has 
a mean temperature 

It -f- l x t x 

l + h' 

JLinear Expansion of Metal.* due to Change of 
Temperature. 

A rod or wire I feet long will, by an increase of temperature of t°, increase 
its length to 

1(1+ at°) feet, 
where a has the following values : — Value of a for 

Metal. F.° C.° 

Zinc .000016540 .00002976 

Lead .000015830 .00002848 

Brass .000010500 .00001890 

Copper .000009560 .00001720 

Iron .000000830 .00001229 

Steel .000006361 .00001145 

Platinum .000004910 .00000884 

Glass .000004870 .00000876 

Specific Meat. 



Element. 


Specific heat 
of equal 
Weights. 


Element. 


Specific heat 
of equal 
Weights. 


Water . . . 
Lithium . . 
Sodium • . . 
Magnesium . 
Aluminum . 
Sulphur . . 
Potassium 
Manganese . 
Iron .... 
Nickel . . . 
Cobalt . . . 
Zinc .... 
Copper . . . 
Bromine (solid) 
Arsenic . . 
Palladium . 








1.0000 
.9408 
.2934 
.2499 
.2143 
.1776 
.1696 
.1140 
.1138 
.1091 
.1070 
.0955 
.0951 
.0843 
.0814 
.0593 


Rhodium 

Silver 

Cadmium 

Tin 

Iodine 

Antimony .... 
Tellurium .... 

Thallium 

Tungsten 

Iridium 

Platinum 

Gold 

Mercury (liquid) . . 

Lead 

Bismuth 

Osmium 


.0580 
.0570 
.0567 
.0562 
.0541 
.0508 
.0474 
.0336 
.0334 
.0325 
.0324 
.0324 
.0333 
.0314 
.0308 
.0306 



COEFFICIENTS. 



185 



If W = "weight of one substance whose temperature is T and specific heat S, 
w = weight of another substance whose temperature is t and specific 
heat s. 

WST + test _ 
WS + ws x ' 

s- ~ i) 



Temperature of mixture 



W (T — t) 

Temperature Coefficients of the Resistivity of Pure 
Copper. 







o 


tc ,_, 






o 


"3 


Temp. 


£ 


- 3 


5 2-3 5 


Temp. 


£ 






'« 


•rfy 


.2-tijg'eS 




'o 


S3 .2 




o 
O 


3£ 

o o 


5 ©"S S 2 

-a .5 S CD - 




O 

O 


c o 


C°. 


F°. 


0°. 


F°. 







32.0 


1. 


0. 


0.14173 


20 


6S.0 


1.07968 


.033294 


0.15302 


1 


33.8 


1.00388 


.001680 


0.14228 


21 


69.8 


1.08378 


.034939 


0.15360 


2 


35.6 


1.00776 


.003358 


0.142S3 


22 


71.6 


1.08788 


.036581 


0.15418 


3 


37.4 


1.01166 


.005036 


0.14338 


23 


73.4 


1.09200 


.038222 


0.15477 


4 


39.2 
42.0 


1.01558 


.006712 


0.14394 


24 


75.2 


1.09612 


.039859 


0.15535 


5 


1.01950 


.008386 


0.14449 


25 


77.0 


1.10026 


.041494 


0.15594 


6 


42.8 


1.02343 


.010059 


0.14505 


26 


78.8 


1.10440 


.043127 


0.15653 


7 


41.6 


1.02738 


.011730 


0.14561 


27 


80.6 


1.10856 


.044758 


0.15711 


8 


46.4 


1.03134 


.013400 


0.14617 


28 


82.4 


1.11272 


.046385 


0.15770 


9 


48.2 


1.03531 


.01506S 


0.14673 


29 


S4.2 


1.11689 


.048011 


0.15830 


10 


50.0 


1.03929 


.016734 


0.14730 


30 


86.0 


1.12107 


.049633 


0.15889 


11 


51.8 


1.04328 


.018399 


0.14786 


40 


104 


1.16332 


.065699 


0.16488 


12 


53.6 


1.01728 


.020082 


0.14843 


50 


122 


1.20625 


.081436 


0.17095 


13 


55.4 


1.05129 


.021723 


0.14900 


60 


140 


1 .24965 


.096787 


0.17711 


14 


57.2 


1.05532 


.023382 


0.14957 


70 


158 


1.29327 


.111687 
.126069 


0.18329 


15 


59.0 


1.05935 


.025039 


0.15014 


80 


176 


1.33681 


0.18946 


16 


60.8 


1.08339 


.026694 


0.15071 


90 


194 


1.37995 


.139863 


0.19558 


17 


62.6 


1.06745 


.028348 


0.15129 


100 


212 


1.42231 


.152995 


0.20158 


18 


64.4 


1.07152 


.029999 


0.15186 












19 


66.2 


1.07559 


.031648 


0.15244 


I 











Heat Conducting- Power of Jfletals. 



Metal. 


Relative heat 

conducting 

power. 


Metal. 


Relative heat 

conducting 

power. 


Silver . . . 
Gold. . . . 
Copper {rolled) 
Copper {cast) 
Aluminum . 
Zinc .... 
Bismuth . . 
Cadmium . . 








100 
98.1 
84.5 
81.1 
66.5 
64.1 
61.0 
57.7 


Iron (bar) 
Tin . . . 
Steel . . 
Platinum 
Sodium . 
Iron {cast) 
Lead . . 
Antimony 










43.6 
42.2 
39.7 
38.0 
36.5 
35.9 
28.7 
21.5 



186 



PROPERTIES OF CONDUCTORS. 



RESISTANCE 1IETALS. 

Following are data on modern resistance metals, supplied by Hermann 
Boker & Co., of 101-103 Duane Street, New York. 

The resistance data are from tests by Helmholtz and the German Impe- 
rial Physical and Technical Institute of Charlottenburg, Germany. 

Dimensions, Resistances, and Weig-hts of Resistance 
Wires. 



6 
ft 




1 




Ohms per 1000 feet. 




Feet per Lb. 
Approxi- 
mately. 




© 
S 

s 


c3 
© 

< 
















a 
O 

02 


o 

© 

w 




© 

"© . 

© 


© 

© 


3*«" 

S * 

Oo2 


© £ !h 

0-^32 


©^ 

002 


14 


.0641 


4107. 


125.9 


73.5 


63.7 


49.7 


56.6 


85. 


79.2 


16 


.0508 


2583. 


200.3 


116.9 


101.4 


78.9 


90.1 


135.3 


125.9 


17 


.0453 


2048. 


252.6 


147.4 


127.8 


99.6 


113.9 


170.6 


158.7 


18 


.0403 


1624. 


318.6 


185.9 


161.2 


125.6 


143.4 


215.5 


200.5 


19 


.0359 


1289. 


401.4 


234.3 


203.1 


158.2 


181.1 


271.0 


252. 


20 


.0320 


1024. 


506.5 


295.6 


256.3 


199.7 


227.9 


342.3 


318.4 


21 


.0285 


812.3 


641.5 


374.4 


324.6 


252.9 


288.7 


433. 


402.6 


22 


.0253 


640.1 


805.7 


470.1 


407.7 


317.5 


362.6 


543.5 


505.5 


23 


.0225 


506.25 


1022.1 


596.6 


517.2 


402.8 


459.9 


689.6 


641.4 


24 


.0201 


404. 


1280.7 


747.6 


648. 


504 9 


576.3 


870. 


809.1 


25 


.0179 


320.4 


1620. 


945.6 


819.7 


638.9 


729. 


1098. 


1021.2 


26 


.0159 


252.8 


2036.5 


1192.9 


1030.5 


802.8 


916.4 


1370. 


1274.1 


27 


.0142 


201.6 


2566.2 


1497.8 


1298.5 


1011.5 


1154.8 


1724. 


1604. 


28 


.0126 


158.8 


3238.1 


1890.1 


1638.5 


1276.4 


1457.1 


2174. 


20?2. 


29 


.0113 


127.7 


4125. 


2407.8 


2087.2 


1626. 


1856.2 


2777. 


2583. 


30 


.0100 


100. 


5148.7 


3005.3 


2605.2 


2029.5 


2316.9 


344S. 


3207. 


31 


.0089 


79.2 


6491.6 


3789.2 


3284.7 


2558.8 


2921.2 


4347. 


4043. 


32 


.0080 


64. 


8187.5 


4779.1 


4142.8 


3227.3 


3684.3 


5555. 


5167. 


33 


.0071 


50.4 


10322. 


6025.1 


5222.9 


4068.9 


4644.9 


7142. 


6600. 


34 


.0063 


39.69 


13020. 


7600.4 


6588.1 


5132.6 


5659. 


9090. 


8354. 


35 


.0056 


31.56 


16416. 


9582.7 


8308.5 


6471.1 


7387.2 


11100. 


10323. 


36 


.005 


25. 


20698. 


12081. 


10473. 


8158.8 


9314.1 


14286. 


13280. 


37 


.0044 


19.83 


26094. 


15229. 


13203. 


10285. 


11743. 


17543. 


16315. 


38 


.004 


16. 


32916. 


19213. 


16655. 


12975. 


14712. 


22220. 


20665. 


39 


.0035 


12.25 


41495. 


24218. 


20996. 


16357. 


18672. 


27700. 


25761. 


40 


.0031 


9.61 


52373. 


30570. 


26500. 


20644. 


23567. 


35714. 


33215. 



RESISTANCE METALS. 



187 



Maximum Amperes for Safe Constant XiOad with 
.Free Radiation. 









Nickeline I. 




B. &S. 
Gauge No. 


Superior. 


la la. 


and 
German 
Silver. 


Nickeline II. 


18 


11.8 


15.75 


17.2 


18.2 


19 


10.25 


13.6 


14.4 


15.6 


20 


8.5 


11.5 


12.1 


13.0 


21 


7.2 


9.7 


10.0 


11.0 


22 


6.0 


8.0 


8.4 


9.1 


23 


5.2 


6.8 


7.1 


7.8 


24 


4.5 


5.8 


6.0 


6.5 


25 


4.0 


4.9 


4.8 


5.5 


26 


3.5 


4.1 


4.1 


4.6 


27 


3.0 


3.6 


3.6 


4.0 


28 


2.7 


3.1 


3.1 


3.5 


29 


2.5 


2.9 


2.9 


3.2 


30 


2.3 


2.7 


2.7 


2.9 


32 


2.0 


2.5 


2.5 


2.63 


34 


1.7 


2.2 


2.2 


2.3 


36 


1.5 


2.0 


2.0 


2.0 







Resistance Ribbon. " Superior " Oracle. 




6 

2° 








Ohms per 


1000 feet. 








2 a 




















)3 M 
H 


|in. 


iin. 


1 i n - 


i in. 


fin. 


fin. 


1 in. 


1 in. 


8 


.128 


25.36 


12.68 


8.45 


6.34 


5.07 


4.22 


3.62 


3.17 


9 


.114 


28.59 


14.29 


9.53 


7.14 


5.71 


4.76 


4.08 


3.57 


10 


.101 


32.22 


16.11 


10.74 


8.05 


6.44 


5.37 


4.60 


4.02 


11 


.0907 


35.93 


17.96 


11.98 


8.98 


7.18 


5.99 


5.13 


5.49 


12 


.0808 


40.19 


20.09 


13.39 


10.04 


8.04 


6.69 


5.74 


5.02 


13 


.0719 


45.61 


22 80 


15.20 


11.40 


9.12 


7.60 


6.51 


5.70 


14 


.0641 


50.72 


25 36 


16.90 


12.68 


10.14 


8.45 


7.24 


6.34 


15 


.0571 


57.18 


28.59 


19.06 


14.29 


11.43 


9.53 


8.16 


7.14 


16 


.0508 


64.44 


32.22 


21.48 


16.11 


12.89 


10.74 


9.20 


8.05 


17 


.0452 


71.86 


35.93 


23.95 


17.96 


14.37 


11.97 


10.26 


8.98 


18 


.0403 


80.38 


39.19 


26.79 


20.09 


16.07 


13.39 


11.48 


10.04 


19 


.0359 


91.22 


45.61 


30.40 


22.80 


18.24 


15.20 


13.03 


11.40 


20 


.0320 


101.44 


50.72 


33.81 


25.36 


20.29 


16.90 


14.50 


12.68 


21 


.0284 


114.36 


57.18 


38.12 


28.59 


22.87 


19.06 


16.33 


14.29 


22 


.0253 


128.88 


64.44 


42.96 


32.22 


25.77 


21.46 


18.41 


16.11 


23 


.0225 


143.72 


71.86 


47.90 


35.93 


28.74 


23.95 


20.53 


17.96 


24 


.0201 


160.76 


80.38 


53.59 


40.19 


32.15 


26.79 


22.96 


20.09 


25 


.0179 


182.44 


91.22 


60.81 


45.16 


36.49 


30.40 


26.06 


22.80 


26 


.0159 


202.88 


101.44 


67.62 


50.72 


40.57 


33.81 


28.98 


25.36 


27 


.0142 


228.72 


114.36 


76.24 


57.18 


45.74 


38.12 


32.67 


28.59 


28 


.0126 


257.76 


128.88 


85.92 


64.44 


51.55 


42.96 


36.82 


32.22 


29 


.0112 


287.44 


143.72 


95.81 


71.86 


57.49 


57.90 


41.06 


35.93 


30 


.0100 


321.52 


160.76 


107.17 


80.38 


64.30 


53.59 


45.93 


40.19 


31 


.0089 


364.88 


182.44 


121.62 


91.22 


72.97 


60.81 


52.12 


45.16 


32 


.0079 


405.76 


202.88 


135.25 


101.44 


81.15 


67.62 


57.96 


50.72 


33 


.0071 


457.44 


228.72 


152.48 


114.36 


91.49 


76.24 


65.33 


57.18 


34 


.0063 


515.52 


257.76 


171.84 


128.88 


103.10 


85.92 


73.64 


64.44 


35 


.0056 


574.88 


287.44 


191.62 


143.72 


114.97 


95.81 


82.12 


71.86 


36 


.005 


643.04 


321.52 


214.34 


160.76 


128.60 


107.17 


91.86 


80.38 


37 


.0044 


729.76 


364.88 


243.25 


1S2.44 


145.95 


121.62 


104.25 


91.22 


38 


.0039 


811.52 


405.76 


270.50 


202.88 


162.30 


135.25 


115.93 


101.44 



The number of feet to the pound of any size of the above ribbon can be 
found by dividing the constant 0.26 by the cross sectional area in square inches, 



188 



PROPERTIES OF CONDUCTORS. 



Resistance Rinuon. la la Quality. 



6 


5^ 






Ohms per 


1000 feet 




























H 


a in. 


Jin. 


fin. 


5 in. 


fin. 


fin. 


fin. 


lin. 


8 


.128 


14.81 


7.40 


4.93 


3.70 


2.96 


2.46 


2.11 


1.85 


9 


.114 


16.69 


8.34 


5.56 


4.17 


3.34 


2.78 


2.38 


2.08 


10 


.101 


18.80 


9.40 


6.26 


4.70 


3.76 


3.13 


2.70 


2.35 


11 


.0907 


20.97 


10.48 


6.99 


5.24 


4.19 


3.49 


2.99 


2.62 


12 


.0808 


23.46 


11.73 


7.82 


5.86 


4.69 


3.91 


3.35 


2.93 


13 


.0719 


26.63 


13.31 


8.87 


6.65 


5.32 


4.43 


3.80 


3.32 


14 


.0641 


29.62 


14.81 


9.87 


7.40 


5.92 


4.93 


4.22 


3.70 


15 


.0571 


33.38 


16.69 


11.12 


8.34 


6.68 


5.56 


4.77 


4.17 


16 


.0508 


37.60 


18.80 


12.53 


9.40 


7.52 


6.26 


5.37 


4.70 


17 


.0452 


41.94 


20.97 


13.98 


10.48 


8.38 


6.99 


5.99 


5.24 


18 


.0403 


46.92 


23.46 


15.64 


11.73 


9.38 


7.82 


6.70 


5.86 


19 


.0359 


53.26 


26.63 


17.78 


13.31 


10.64 


8.87 


7.60 


6.65 


20 


.0320 


59.24 


29.62 


19.75 


14.81 


11.84 


9.87 


8.46 


7.40 


21 


.0284 


66.76 


33.38 


22.25 


16.69 


13.35 


11.12 


9.53 


8.34 


22 


.0253 


75.20 


37.60 


25.07 


18.80 


15.04 


12.53 


10.74 


9.40 


23 


.0225 


83.88 


41.94 


27.96 


20.97 


16.77 


13.98 


11.98 


10.48 


24 


.0201 


93.84 


46.92 


31.28 


23.46 


18.77 


15.64 


13.40 


11.73 


25 


.0179 


106.52 


53.26 


35.50 


26.63 


21.30 


17.78 


15.21 


13.31 


26 


.0159 


118.48 


59.24 


39.49 


29.62 


23.69 


19.75 


16.91 


14.81 


27 


.0142 


133.52 


66.76 


44.50 


33.38 


26.70 


22.25 


19.07 


16.69 


28 


.0126 


150.40 


75.20 


50.13 


37.60 


30.08 


25.07 


21.50 


18.80 


29 


.0112 


167.76 


83.88 


55.92 


41.94 


33.55 


27.96 


23.96 


20.97 


30 


.0100 


187.68 


93.84 


62.56 


46.92 


37.53 


31.28 


26.81 


23.46 


31 


.0089 


213.04 


106.52 


71.01 


53.26 


42.60 


35.50 


30.43 


26.63 


32 


.0079 


236.96 


li8.*8 


78.98 


59.24 


47.40 


39.49 


33.82 


29.62 


33 


.0071 


267.U4 


133.o2 


89.01 


66.76 


53.40 


44.50 


38.15 


33.38 


34 


.0063 


300.80 


150.40 


100.26 


75.20 


60.16 


50.13 


42.97 


37.60 


35 


.0056 


335.52 


167.76 


111.84 


83.88 


67.10 


55.92 


47.93 


41.94 


36 


.005 


375.36 


187.68 


125.12 


93.84 


75.07 


62.56 


53.62 


46.92 


37 


.0044 


426.08 


213.04 


142.02 


106.52 


85.21 


71.01 


60.87 


53.26 


38 


.004 


473.92 


236.96 


157.97 


118.48 


94.78 


78.98 


67.64 


59.24 



Specific Resistance and Temperature Coefficient. 



Material. 



Superior 

la la, hard 

la la, soft 

Nickeline No. II., hard 
Nickeline No. II., soft . 
Nickeline No. I., hard . 
Nickeline No I., soft . 
German Silver, average 

Manganin 

Constantin ..... 



Specific 
Resistance 

at 20° C. 
microhms. 



85.4 to 

86.5 

50.2 

47.1 

33.9 

32.3 

43.6 

40.7 

31.5 

47.5 

50. — 52 



Coefficient for 
1°C. 



+ .00067 to 
+ .00073 
— .000011 
+ .00o005 
-f -000168 
+ .000181 
+ .000076 
-f .000077 
-f -00025 
± .00001 
+ .00001 



"SUPERIOR" WIRE. 

Specific gravity, 8.4. 

Specific resistance at 20° C, 86 microhms. 

Coefficient of temperature, mean value, for 1° C, -f- 0.00065. 



BOKER S WIRES. 



189 



Resistance of one circular mil foot of " Superior " wire at 20° C, 517^5 
ohms. 

This resistance material does not rust, nor show any sign of oxidation at 
ordinary temperature, and it shows no sign of deterioration after being sub- 
mitted to a temperature just below a visible red heat as a permanent load. 



Prices of JBare Wire per Pound. 



B. &S. 

Gauge. 


Inch. 


Superior. 


la la. 


Nickeline 
I. 


JSfickeline 
II. 


15 and 
heavier 


.057 


$1.07 


$.078 


$0.66 


$.61 


16 


.05082 


1.09 


.80 


.69 


.63 


17 


.04525 


1.09 


.80 


.69 


.63 


18 


.0403 


1.09 


.80 


.69 


.63 


19 


.0358 


1.09 


.80 


.69 


.63 


20 


.0319 


1.09 


.80 


.69 


.63 


21 


.0284 


1.12J 


.85 


.72 


.66 


22 


.0253 


1.16 


.88 


.75 


,70 


23 


.0225 


1.16 


.88 


.75 


.70 


24 


.0201 


1.24 


.94 


.78 


.74 


25 


.0179 


1.26 


.96 


.83 


.77 


26 


.0159 


1.28 


.96 


.85 


.79 


27 


.01419 


1.33 


1.04 


.90 


.84 


28 


.01264 


1.37 


1.09 


.94 


.88 


29 


.01125 


1.40 


1.12 


.97 


.91 


30 


.010 


1.45 


1.17 


1.02 


.96 


31 


.00892 


1.52 


1.24 


1.09 


1.03 


32 


.00795 


1.60 


1.33 


1.16 


1.10 


33 


.00708 


1.69 


1.45 


1.26 


1.20 


34 


.0063 


1.81 


1.55 


1.38 


1.33 


35 


.0056 


1.98 


1.75 


1.55 


1.49 


36 


.005 


2.56 


2.20 


2.13 


2.07 


37 


.00445 


4.21 


3.85 


3.72 


3.72 


38 


.00396 


6.36 


6.00 


5.93 


5.87 


39 


.00353 


8.11 


7.75 


7.68 


7.62 


40 


.00314 


10.36 


10.00 


9.93 


9.87 




.00196 


15.60 


15.25 


15.18 


15.12 



190 



PROPERTIES OF CONDUCTORS. 



Prices of Silk Covered Wire per Pound. 



bo 

P 
a 




Superior. 


la la. 


Nickeline I. 


Nickeline II. 


O 




d) 




<s 




6 




<v 




a 


6 


2 

p 
o 


6 


2 

P 
o 


6 
"So 

p. 


3 

p 

o 


6 

Ml 

a 


2 

p 
o 


w 




53 


ft 


53 


ft 


55 


ft 


55 


ft 


20 


.031 and 
heavier 


$1.90 


$2.60 


$1.50 


$2.20 


$1.52 


$2.22 


$1.47 


$2.17 


21 


.0284 


2.00 


2.70 


1.60 


2.30 


1.62 


2.32 


1.57 


2.27 


22 


.0253 


2.05 


2.75 


1.65 


2.35 


1.67 


2.37 


1.62 


2.32 


23 


.0225 


2.10 


2.80 


1.70 


2.40 


1.72 


2.42 


1.67 


2.37 


24 


.0201 


2.15 


2.90 


1.75 


2.50 


1.77 


2.52 


1.72 


2.47 


25 


.0179 


2.30 


3.10 


1.90 


2.70 


1.92 


2.72 


2.87 


2.67 


2<; 


.0159 


2.50 


3.30 


2.10 


2.90 


2.12 


2.92 


2.07 


2.87 


27 


.0141 


2.70 


3.60 


2.30 


3.20 


2.32 


3.22 


2.27 


3.17 


28 


.0126 


2.85 


3.90 


2.45 


3.50 


2.47 


3.52 


2.42 


3.47 


2!) 


.01125 


3.15 


4.20 


2.75 


3.80 


2.77 


3.82 


2.72 


3.77 


30 


.010 


3.40 


4.50 


3.00 


4.10 


3.02 


4.12 


3.00 


4.07 


31 


.0089 


3.70 


4.90 


3.30 


4 50 


3.32 


4.52 


3.27 


4.47 


32 


.0079 


4.10 


5.30 


3.70 


4.90 


3.72 


4.92 


3.67 


4.87 


33 


.0070 


4.40 


5.90 


4.00 


5.50 


4.02 


5.52 


4.00 


5.47 


34 


.0063 


4.90 


6.40 


4.50 


6.00 


4.52 


6.02 


4.47 


5.97 


35 


.0056 


5.70 


7.00 


5.30 


6.60 


5.32 


6.62 


5.27 


6.57 


36 


.005 


6.90 


8.65 


6.50 


8.25 


6.52 


8.27 


6.47 


8.22 


37 


.00445 


9.90 


12.40 


9.50 


12.00 


9.52 


12.02 


9.47 


11.97 


38 


.0039 


12.40 


16.90 


12.00 


16.50 


12.02 


16.52 


12.00 


16.47 


39 


.00353 


15.40 


20.40 


15.00 


19.50 


15.02 


19.52 


15.00 


19.47 


40 


.00314 


18.40 


22.90 


18.00 


22.50 


18.02 


22.52 


18.00 


22.47 



The above prices are for wire, single or double, covered with green or 
white silk. 





Prices of Resistance ft fleets per Pound 




B. &S. 

Gauge. 


Inch. 


Superior. 


la la. 


Nickeline 
I. 


Nickeline 
11. 


28 and 
heavier 


.0126 


$1.02 


$0.69 


$0.63 


$0.57 


29 


.01125 


1.0 6 


.71 


.65 


.60 


30 


.010 


1.05 


.71 


.65 


.60 


31 


.0089 


1.07 


.74 


.67 


.62 


32 


.0079 


1.07 


.74 


.67 


.62 


33 


.007 


1.09 


.76 


.69 


.65 


34 


.0063 


1.09 


.76 


.69 


.65 


35 


.0056 


1.11 


.78 


.72 


.66 


36 


.005 


1.11 


.78 


.72 


.66 


37 


.0044 


1.11 


.78 


.72 


.66 


38 


.0039 


1.11 


.78 


.72 


.66 



The above prices are for sheets of maximum width of 12 inches, and max- 
imum length of 7 to 8 feet. 



KRUPP'S RESISTANCE WIRES. 



191 



Prices for Resistance Tapes in ionjr lengths per Pound. 



B.&S. 
Gauge. 


Inch. 


Superior. 


la la. 


Nickeline 
I. 


Nickeline 
II. 


18 and 
heavier 


.0403 


$1.08 


$0.73 


$0.66 


$0.61 


19 


.0358 


1.10 


.74 


.67 


.62 


20 


.0319 


1.10 


.74 


.67 


.62 


21 


.0284 


1.10 


.74 


.67 


.62 


22 


.0253 


1.10 


.74 


.67 


.62 


23 


.0225 


1.10 


.74 


.67 


.62 


24 


.0201 


1.10 


.74 


.67 


.62 


25 


.0179 


1.10 


.74 


.67 


.62 


26 


.0159 


1.10 


.74 


.67 


.62 


27 


.0141 


1.10 


.74 


.67 


.62 


28 


.0126 


1.10 


.74 


.67 


.62 


29 


.01125 


1.14 


.77 


.70 


.65 


30 


.010 


1.14 


.77 


.70 


.65 


31 


.0089 


1.17 


.79 


.73 


.67 


32 


.0079 


1.17 


.79 


.73 


.67 


33 


.007 


1.21 


.83 


.76 


.70 


34 


.0063 


1.21 


.83 


.76 


.70 


35 


.0056 


1.30 


.87 


.80 


.75 


36 


.005 


1.30 


.87 


.80 


.75 


37 


.0044 


1.30 


.87 


.80 


.75 


38 


.0039 


1.30 


.87 


.80 


.75 



The above prices are tapes about f-inch wide and narrower. Maximum 
length of tapes is about 300 feet. 



KREPP'S RESISTANCE WIRES, 

Following will be found data of the Krupp resistance wires supplied by 
the American agents, Thomas Prosser & Son, 15 Gold Street, New York. 

Krapp'i Resistance llletals. 

Specific gravity 8.102 

Specific resistance at 20° C. mean ...... 85.13 microhms. 

Temperature coefficient, mean 0007007. 

Resistance per circular mil-foot 314.067 obms. 

Resistance per 1000', 1 square inch area 8513 ohms. 

This metal can be permanently loaded with current sufficient to raise its 
temperature to 600° C. (1112° F.) without undergoing any structural change. 



192 



PROPERTIES OF CONDUCTORS, 



Table of Krupp's Resistance Wires* 



Diam. 


Diam. 
in inches. 


Near- 
est 
B. &S. 

Gauge 


Feet 
per 
lb. 


Resistance 


in ohms per foot. 


in m.m. 


at 


at 


at 


at 






No. 




68° F. 


176° F. 


284° F. 


428° F. 


5 


.1968 


4 


9 


.0132 


.0138 


.0143 


.0150 


4* 


.1772 


5 


12 


.0163 


.0170 


.0176 


.0184 


4 


.1575 


6 


15 


.0206 


.0215 


.0224 


.0235 


3£ 


.1378 


7 


19 


.0269 


.0280 


.0291 


.0307 


3 


.1181 


9+ 


26 


.0368 


.0382 


.0396 


.0417 


2| 


.1083 


9— 


31 


.0437 


.0455 


.0472 


.0497 


2| 


.0984 


10 


37 


.0528 


.0550 


.0570 


.0601 


21 


.0885 


11 


46 


.0653 


.0679 


.0705 


.0742 


2 


.0787 


12 


58 


.0825 


.0860 


.0892 


.0940 


If 


.0689 


13 


76 


.1078 


.112 


.116 


.123 


1* 


.0590 


15 


104 


.1468 


.153 


.159 


.167 


li 


.0492 


16 


150 


.2115 


.220 


.229 


.241 


1 


.0393 


18 


234 


.3305 


.344 


.356 


.376 


1 


.0295 


21 


415 


.5870 


.610 


.633 


.667 


* 


.0196 


24 


937 


1.324 


1.38 


1.43 


1.51 



Price JList per Pound. 

B. & S. Nos. 4 to 10 inclusive 
B. & S. Nos. 11 to 12 inclusive 
B. & S. Nos. 13 to 15 inclusive 

B. & S. No. 16 

B. & S. No. 18 

B. & S. No. 21 

B. & S. No. 24 



$1.10 
1.15 
1.20 
1.25 
1.30 
1.35 
1.40 



Table of Specific Resistance. 



Substance. 



Metals at 0° C. 

Copper (annealed) . . 
Copper (hard) . . . 
Silver (annealed) . . 
Silver (hard) . . . . 

Gold 

Aluminum (annealed) 

Platinum 

Iron (pure) 

Iron (telegraph wire) . 

Lead 

Mercury 

Sileniuin 

Carbon (graphite) . . 
Carbon arc light) . . 



Specific 




resistance 


Relative 


in microhms 


conductance. 


per cubic cm. 




1.570 


100. 


1.603 


98.1 


1.492 


105 


1.620 


98 


2.077 


76 


2.889 


54 


8.982 


17 


9.638 


16 


15. 


10 


19.63 


8.3 


94.34 


1.6 


6 X 10™ 


3?5 1)515 OUtfffffiJ 


2100 to 42000 




about 4000 


2Sao 



RESISTANCE OF DIELECTRICS. 193 

Table of Specific Resistance — Continued. 





Specific 






resistance 


Relative 


Substance. 


in microhms 
per cubic cm. 


conductance. 


Alloys. 






German silver (Cu 60, Zn 26, M 14) . . 


20.76 


7-6 


Platinum-Silver (Pt 67, Ag 33) . . . 
Platinoid (Cu59, Zn 25.5, Ni 14, W 55) 




24.4 


6.5 




32.5 


4.8 


Manganin (Cu 84, Ni 12, Mn 3.5) . . 




47.5 


3.3 


Superior 








86. 




la la, hard .... 














50.2 




la la, soft .... 














47.1 




Nickeline I., hard . 














43.6 




Nickeline I., soft . 














40.7 




Nickeline II., hard 














33.9 




Nickeline II., soft . 














32.3 




Krupp's metal . . 














85.13 




Constantin .... 














50 to 52 




John A. Roebling's Son's Co., Climax 




78.5 




Liquids at 18° C. 






Pure water 


26.5 X 10 8 




Dilute H 2 S0 4 5% 


486 X 10 4 




H 2 S0 4 30 % 


137 X 10* 




H 2 SO 4 80% 


918 X 10* 




Zn S0 4 24% 


214 X 10 5 




HNO 3 30% 


129 X 10 4 




Insulators. 






Glass at 20° C 


91 X 10 18 




Glass at 200° C 


22.7 X 10 12 




Gutta-percha 24° C 


4.5 X 10 20 





RESISTANCE OF DIEIECTRICi. 

Insulating materials or non-conductors, such as glass, wood, india-rubber, 
gutta-percha, etc., are termed dielectrics, and vary in resistance, not only 
with the material, but with its kind and quality. 

The following table gives the 





Specific Resistance of Insulators. 


Material. 


Resistance in 

megohms per 

cubic centimeter. 




84 X 10" 


Gutta-percha 


450 X 10° 
9000 X 10" 




28000 X 10" 







194 PROPERTIES OF CONDUCTORS. 

Specific Resistance of Insulators. — Continued, 



Material. 


Resistance in 

megohms per 

cubic centimeter. 


Hooper's Compound 

Paraffine -. 


15000 x 10 u 

34000 X 10 6 

8x lO 6 

1 X 10 6 

.35 X 10 6 

350 X 10 6 

14 X 10 B 

1670 x 10 6 

450 X 10 6 


Paraffine oil 


Olive oil 


Lard oil 


Stearic acid 




Wood tar .... 







Disruptive Value of Dielectrics. 

In a paper on the " Dielectric Strength of Air," June 27, i898, before the 
Am. Inst. E. E., Chas. P. Steinmetz gave the results of numerous tests with 
different shapes of electrodes and under various conditions. Following 
are his conclusions and some of his tables and curves. 

1st. At constant voltage and constant wave shape, that is constant ratio 
between maximum and effective E.M.F., the striking distance is a constant, 
especially between sharp points, where the tests have been repeated over 



w 


-M- 


-/ 


_z 


7- 


j ' - 


T^ 


7 


_^_ 


'/' 


/ 


_j 


jC- 


J? 


>T / 



2 7 
6 
& 
4 
3 



10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 
KILOVOLTS EFFECTIVE 

Fig. 0. Points, Smooth Core Alternator, 125 Cycles. 

and over again, and independent of the atmospheric condition, the frequency, 
etc., to such an extent that the striking distance between needle points 
offers the most reliable means to determine very high voltages. For this 
reason, it is used in this manner as final check in all high potential insula- 



tion tests of the General Electric Company. 



DISRUPTIVE VALUE OF DIELECTRICS. 



195 



2d. No physical law lias been found to represent satisfactorily all the 
observations. Some point to the existence of a constant dielectric strength 
of air, analogous to the tensile strength of mechanics. Others point to the 
existence of a spurious counter E.M.F. of the spark or transition resistance 
from electrode to air. 

3d. Constant dielectric strength. Cylinders of 1.11 in. diameter give an 
average disruptive strength of air of 60 kilovolts per inch. Cylinders of 
.315 in. diameter, an average dielectric strength of 77. Spheres at very 
small distance point toward the latter value. As a disturbing factor in this 
case, enters the electrostatic brush discharge, Avhich by a partial breakdown 
of the air surrounding the electrodes changes and increases the size and 
decreases the distance of the effective terminals. 



3.0 
















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20 


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10 20 30 40 50 60 70 80 90 100 110 120 130 140 

KILOVOLTS EFFECTIVE 

Fig. 0. Comparison of Points and Spheres. Smooth Core 
Alternator, 125 Cycles. 



4th. Counter E.M.F. of the sparks. The tests with sharp points give 22 
kilovolts, or 11 kilovolts for a single transition from terminal to air. Spheres 
give curves pointing to a similar phenomenon. Electric conductors in- 
serted at right angles into or parallel with the discharge, point to the exis- 
tence of a counter E.M.F. of the same magnitude. The beginning of the 
electrostatic brush discharge is at a potential of this magnitude also. 



196 



PROPERTIES OF CONDUCTORS. 



TABLE. — Points. 
2\" needles. 125 cycles. 



Smooth Core Alternator 
A-10-30-1500. 



Ironclad Alternator 
A-10-60-1500. 



O to 


Kilovolts: effective. 




Kilovolts : effective. 




S <u 








- © 












dA 








u 












+3 V 


















.2 s< 
A"" 


# 


OS ..-( 
~l ^ 


bo 

u 

<v 


t/3 r+ 

S"" 

d. 




e« g 


<v 
bfi 

U 

<D 


P* be 
. p 

3 a 


lO g" 




L~ 


t- 


< 




t~ 


ha"* 


< 


ha -a 


►» s 


.25 


4.25 






.25 


4.13 










.5 


10.0 






.5 


9.0 


10.0 


9.5 


11.0 


14.5 


1.0 


20.4 






1.0 


16.0 


18.5 


17.7 


22.0 


25.3 


1.5 


29.3 






1.5 


24.3 


26.0 


25.1 


31.0 


35.5 


2.0 


35.2 






2.0 


30.5 


30.5 


30.5 


38.0 


43.0 


2.5 


40.4 






2.5 


33.9 


35.0 


34.4 


43.5 


50.3 


3.0 


45,6 






3.0 


36.3 


38.0 


37.1 


48.0 


54.5 


3.5 


49.4 






3.5 


42.2 


41.7 


42.0 


51.0 


63.0 


4.0 


52.5 






4.0 


41.3 


45.0 


43.2 


55.5 




4.5 


59.6 






4.5 


45.5 


48.0 


46.7 


61.0 




5.0 




61.0 




5.0 


48.4 


50.5 


49.5 






5.5 




65.7 




5.5 


53.0 


55.0 


54.0 






6.0 


69.8 


69.5 


69.65 


6.0 


56.1 


58.8 


57.4 






6.5 


73.4 


74.7 


74.05 


6.5 


59.8 


62.0 


60.9 






7.0 


77.5 


79.2 


78.35 


7.0 


63.3 


64.7 


64.0 






7.5 


83.8 


83.0 


83.4 


7.5 


67.5 


69.0 


68.3 






8.0 


86.8 


87.3 


87.05 


8.0 


70.9 


73.4 


72.1 






8.5 


90.5 


90.2 


90.35 


8.5 


75.8 


76.0 


75.9 






9.0 


95.0 


93.7 


94.35 


9.0 


79.8 


79.2 


79.5 






9.5 


97.7 


96.3 


97.0 


9.5 


84.8 


82.5 


83.6 






10.0 


101.5 


99.0 


100.25 


10.0 


88.8 


86.4 


87.6 






10.5 


107.0 


103.0 


105.0 


10.5 


93.5 


89.5 


91.5 






11.0 


111.5 


107.5 


109.5 


11.0 


97.7 


93.0 


95.4 






11.5 


114.0 


110.5 


112.5 


11.5 


102.0 










12.0 


121.0 


116.0 


118.5 


12.0 


107.7 










12.5 


125.5 


120.0 


122.75 


12.5 


111.0 










13.0 


133.0 


123.0 


128.0 


13.0 


117.5 










13.5 


135.0 


127.0 


131.0 


13.5 


122.5 










14.0 


140.0 


129.0 


134.5 


14.0 


128.0 










14.5 


144.0 


136.0 


140.0 


14.5 


134.4 










15.0 


150.0 






15.0 


138.3 










15.5 


155.0 


\ 
















16.0 


159.5§ 



















* 85° F. Weather sultry. 

t 75°-80° P. Weather clear and hright. 

$ 70° F. Weather cool and cloudy. 

§ Internal discharges in intermediary transformers F' F", 



VALUES OF VARIOUS DIELECTRICS. 



197 

































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A 


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/ 


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/- 


c?" 










oo 9 

111 
















*f 


1 














o 8 


















j? 






























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/ 


o- 




























/ 


' 




























' / 


% 






























#/ 


<? 


























s 


^ 
























" 


-rf* 































Fig. 0. 



10 20 30 40 50 60 70 80 90 100 110 120 130 
KILOVOLTS EFFECTIVE 

Points in Air. Fog and Steam at Atmospheric Pressure. 
Ironclad Armature, 125 Cycles. 



Values of Various Dielectrics. 

Steinmetz, February, 1893. A. I. E. E. 





Electrostatic 
gradient at 


Formula for 
Calculating the 


Material. 





5 


25 


Sparking Distance. 




Kilovolts, 

in Kilovolts per 

Centimeter. 


B 
E — P. D. in 

Kilovolts. 


Air 


139 

4170 

130 


16.7 
3200 

52 
130 
339 

81 

80 

64 

30 

16 
36 
43 
10.1 


11.9 

1660.0 

15.3 

.86 




Mica 

Vulcanized fiber, red . . . 

Dry wood fiber 

Parafiined paper .... 
Melted parafiine .... 
Boiled linseed oil ... . 

Turpentine oil 

Copal varnisli 

Crude lubricating oil (min- 
eral oil) 

Vulcabeston 

Asbestos paper 

Creeping discharge . . . 


B = .24 E + .0145 E 2 
B = 7.66 E + 2.3 E 2 
B — 7.66 E 
D = 3E 
B — 12.4 E 
B — 12.5 E 
B — 15.7 E 
B = 30E 

B = WE 
B=28E 
B = 23E 

B = 55(E — 2) 2 



198 PROPERTIES OF CONDUCTORS. 



Tests of Vulcanized I ndia-Rnbber. 

Lieutenant L. Vladomiroff, a Russian naval officer, has recently carried 
out a series of tests at the St. Petersburg Technical Institute with a view to 
establishing rules for estimating the quality of vulcanized India-rubber. 
The following, in brief, are the conclusions arrived at, recourse being had 
to physical properties, since chemical analysis did not give any reliable 
result: 1. India-rubber should not give the least sign of superficial crack- 
ing when bent to an angle of 180 degrees after five hours of exposure in 
a closed air-bath to a temperature of 125° C. The test-pieces should be 2.4 
inches thick. 2. Rubber that does not contain more than half its weight of 
metallic oxides should stretch to five times its length without breaking. 

3. Rubber free from all foreign matter, except the sulphur used in vulcan- 
izing it, should stretch to at least seven times its length without rupture. 

4. The extension measured immediately after rupture should not exceed 12% 
of the original length, with given dimensions. 5. Suppleness may be deter- 
mined by measuring the percentage of ash formed in incineration. This 
may form the basis for deciding between different grades of rubber for 
certain purposes. 6. Vulcanized rubber should not harden under cold. 
These rules have been adopted for the Russian navy. — Iron Age, June 15, 
1893. 

GUTTA-PERCHA. 

Specific gravity, 0.9693 to 0.981. 

Weight per cubic foot, 60.56 to 61.32 pounds. 

Weight per cubic inch, 0.560 to 0.567 oz. 

Softens at 115 degrees F. 

Becomes plastic at 120 degrees F. 

Melts at 212 degrees F. 

Oxidizes and becomes brittle, shrinks and cracks when exposed to the air, 
especially at temperatures between 70 and 90 degrees F. 

Oxidation is hastened by exposure to light. 

Oxidation may be delayed by covering the gutta-percha insulation with a 
tape which has been soaked in prepared Stockholm tar. 

Where gutta-percha is kept continually under water there is no notice- 
able deterioration, and the same applies where gutta-percha leads are cov- 
ered with lead tubing. 

Stretched gutta-percha, such as is used for insulating cables, will stand 
a strain of 1,000 pounds per square inch before any elongation. 

The breaking strain is about 3,500 pounds per square inch. 

The tenacity of gutta-percha is increased by stretching it. 

Where Z)=r diameter of gutta-percha insulation, and cl = diameter of con- 
ductor of copper (both dimensions in mils) the weight of gutta-percha per 

knotls ~l9i-- 

When w = weight of stranded copper conductor per knot in pounds, and 
W = weight of gutta-percha per knot in pounds, then outer diameter 

= V70.4 w -f- 491 W mils. 

If the conductor is solid, then, outer diameter 

— V55 w -f 491 W mils. 

After one minute's electrification, the insulation resistance per knot 
of best quality gutta-percha insulated cable will be, 

e- rr 769 (log D — log d.) megohms at 75° F. 

Resistance of Outta-JPercha under Pressure. — The resistance 
of gutta-percha under pressure increases according to the following formula, 
when R = the resistance at the pressure of the atmosphere, and r the resis- 
tance at p pounds per square inch. 

r = R (1 + 0.00023^). 



GUTTA-PERCHA. 199 



Resistance of CJutta-Percha decreases with Rise of Tem- 
perature. — The resistance of gutta-percha decreases, as per the follow- 
ing formula as the temperature rises, where 

R =z resistance at the low temperature, 
r = resistance at the high temperature, 
t = difference in temperature, degrees F. ; 

then log R = log r — t log 0.9399, 

and log r = log R + Hog 0.9399. 

Capacity and Resistance of Gutta-Percha. 

The resistance of a plate of gutta-percha one foot square and .001 inch 
thick = 1.066 megohms at 75° F. The electrostatic capacity of the same 
piece at the same temperature is .1356 microfarads. 

The product of the resistance in megohms by the electrostatic capacity 
in microfarads, both taken at 75° F., after one minute's electrification = 
.144 

Ratio of T> -f- d for strand and solid conductors. 



For stranded conductor insulated with gutta-percha., 



§=^ 



W 

1 + 6.97—. 



For solid conductor insulated with gutta-percha, 



5 = l/ 1 + 8 .935. 
d " ' w 

In which T> = outer diameter of cable, 

and d = diameter of conductor, 

and W and to = weight of gutta-percha and of conductor respectively in 
pounds. 

The approximate electrostatic capacity of a gutta-percha insulated cable 

per knot is 

1877 

microfarads. 



log D — log d 



The electrostatic capacity of a gutta-percha insulated cable compared with 
one of the same size insulated with india rubber is about as 120 is to 100. 

Jointing- Grutta Percha Covered Wire. 

First remove the gutta-percha for about two inches from the ends of the 
wires which are to be jointed. Fig. 4. 



Fig. 4. 

Next cross the wires midway from the gutta-percha, and grasp with the 
pliers. Fig. 5. 




Fig. 5. 



200 PROPERTIES OF CONDUCTORS. 

Then twist the wires, the overlapping right-hand wire first, and then, 
reversing the grip of the pliers, twist the left-hand wire over the right. Cut 
off the superfluous ends of the wires and solder the twist, leaving it as shown 
in Fig. 6. 



Fig. 6. 

Next warm up the gutta percha for ahout two inches on each side of the 
twist. Then, first draw down the insulation from one side, half way over 



Fig. 7. 

the twisted wires, Fig. 7, and then from the other side in the same way, Fig. 8. 



Fig. 8. 

Then tool the raised end down evenly over the under half with a heated 
iron. Then warm up the Avhole and work the " drawdown " with the thumb 
and forefinger until it resembles Fig. 9. Now allow the joint to cool and set. 



Fig. 9. 

Next roughen the drawdown with a knife, and place over it a thin coating 
of Chatterton's compound for one inch, in the center of the drawdown, 
which is also allowed to set. 

Next cat a thick strip of gutta-percha, about an inch wide and six inches 
long, and wrap this, after it has been well warmed by the lamp, evenly over 
the center of the drawdown. Fig. 10. 



Fig. 10. 

The strip is then worked in each direction by the thumb and forefinger 
over the drawdown until it extends about 2 inches from center of draw- 
down. Then tool over carefully where the new insulation joins the old, 
after which the joint should be again warmed up and worked with the fore- 
finger and thumb as before. Then wet and soap the hand, and smooth and 
round out the joint as shown in Fig. 11. 



Fig. 11. 

Between, and at every operation, the utmost care must be exercised to 
remove every particle of foreign matter, resin, etc. 



JOINTS IN CABLES. 



201 



Joints in Rubber Insulated Cables. 

Preparation of Ends.-Remove the outside protecting braid or 
tape, and bare the conductor of its rubber insulation for two or three inches 
back from the end. Clean the metal carefully by scraping with a knife or 
with sandpaper. 

IVEetal Joint. — If solid conductor, scarf the ends with a file so as to 
give a good long contact surface for soldering. If conductor is stranded, 
carefully spread apart the strands, cutting out the centres so conductors 
can be butted together, the loose ends interlacing as in Fig. 9, and bind 
wires down tight as in Fig. 10. with gas or other pliers. Solder carefully, 




Fig. 10. 



using no acid ; resin is the best, although jointers often use a spermaceti 
candle as being handy to use and easy to procure. Large cables are easiest 
soldered by dipping the joint into a pot of molten solder, or by pouring the 
molten metal over the joint. 

The insulation of all kinds of joints is done in the same manner, the only 
difference in the joint being the manner in which the conductors are joined 
together. Following are some of the styles of joining conductors, which 
are afterward insulated with rubber, and covered with lead when necessary. 





Fig. 11. 



Fig. 12. 




Figs. 13-14. 



Seeley's Cable Connectors. —The cuts below show a style of cop- 
per connectors very handy in joining cables. They are copper tinned over, 
and after putting in place can be " sweated" on with solder ; when dry can 
be insulated as previously described. 




Figs. 15-16. 



202 PROPERTIES OF CONDUCTORS. 



Insulating- tlie .Joint. — Jointers must have absolutely dry and 
clean hands, and all tools must be kept in the best possible condition of 
cleanliness. Clean the joint carefully of all flux and solder ; scarf back the 
rubber insulation like a lead-pencil for an inch or more with a sharp knife. 

Carefully wind the joint with three layers of pure unvulcanized rubber, 
taking care not to touch the strip with the hands any more than neces- 
sary ; over this wind red rubber strip ready for vulcanizing. Lap the tape 
upon the taper ends of the insulation, and make the covering of the same 
diameter as the rubber insulation on the conductor, winding even and 
round. Cover the rubber strip with two or three layers of rubber-saturated 
tape. 

Xiead covering-. — If the insulation is covered and protected by lead, a 
loose sleeve is slipped over one end before jointing, and slipped back over 
the joint when the insulation is finished, a plumber's wiped joint being 
made at the ends. 




Fig. 17. 

Joints in Waring Cables. — This cable is covered with cotton, 
thoroughly impregnated with a composition of hydro-carbon oils applied at 
high temperature, the whole being covered with lead to protect the insula- 
tion. The insulating properties of this covering are very high if the lead is 
kept intact. 

Metal joints are made as usual, and a textile tape may be used for cover- 
ing the bare copper. A large lead-sleeve is then drawn over the joint, 
and wiped onto the lead covering at either end ; then the interior space is 
filled with a compound similar to that with which the insulation is im- 
pregnated. 

Joints in Paper Insulated Cables. — This cable is covered or 
insulated with narrow strips of thin manila paper wound on spirally, after 
which the whole is put into an oven and thoroughly dried, then plunged 
into a hot bath of resin oil, which thoroughly impregnates the paper. This 
insulation is not the highest in measurement, but the electrostatic capacity 
is low and the breakdown properties high. When used for telephone pur- 
poses the paper is left dry, and is wound on the conductor very loosely, thus 
leaving large air spaces and giving very low electrostatic capacity. 

Joints are made as in the AVaring cable by covering the conductor with 
paper tape of the same kind as the insulation, theu pulling over the lead 
sleeve, which is finally filled with paraffine wax. 

Hundreds of miles of such cables being thus employed at pressures ran- 
ging from 500 to 10,000 volts — notably in the Metropolitan district of New 



Cost of Straight or Sleeve Joints Insulated with Rubber. 

On rubber-insulated, lead-covered cable. 

Plumber 1 hour .25 

Insulator \ hour .15 

Helper 1 hour .15 

Red rubber 1 oz. @ $1.00 per lb. .07 

Pure rubber 1 oz. @ $2.00 per lb. .15 

Grimshaw tape 1 oz. @ .50 per lb. .03 



UNDERGROUND CONSTRUCTION. 203 



Copper sleeve .035 

Lead sleeve .06 

Solder , U lbs. @ .20 .30 

Pasters . . . . 2 .005 

Coal .10 

Candle (for flux) .01 

Total ........ $1.31 



Cost of T Joint on Rubber Insulated Cable. 

Ton rubber-insulated lead-covered cable. 

Plumber l^hour $.375 

Insulator .....,,.. f hour .225 

Helper . . H bour .225 

Red rubber U oz. @ $1.00 per lb. .11 

Pure rubber ■ . . \\ oz. @ 2.00 per lb. .23 

Grimshaw tape . : \\oz.@ .50 per lb. .05 

Solder . 2 lbs. @ .20 per lb. .40 

Lead T .26 

Copper T .075 

Pasters .0075 

Candle ........... .0125 

Coal .10 

Total ........ $2.07 

IUVDERGBOIJirD EIEC1BICAL CONSTRUCTION. 

Mr. Louis A. Ferguson, in paper before tbe National Electric Light Asso- 
ciation in May, 1899, gives tbe results of bis observations as to tbe cost of 
laying and maintaining underground conductors. Labor, fittings, paving, 
and laying one length of Edison main tube costs from $5.45 in unimproved 
streets, with no paving, to $29.81 in asphalt. The annual cost of supervision 
and maintenance amounts to 1.9% per annum of the original investment. 

The total cost per duct foot of laid conduit of various types is given in the 
following table, where the higher price is for asphalt pavement, and the 
lower one for no pavement. 

National conduit ... In groups of 2 or 4 16.74 to' 57.24 cents. 

Francis conduit .... " " 14.66 to 55.16 " 

Lithocite conduit ... " " 15.18 to 55.68 " 

Camp tile " " 14.14 to 54.64 " 

Three-inch iron pipe . . " " 22.50 to 66.00 " 

Manholes as used in Chicago cost for size 2'x2'x 3' from $32.18 to $38.63 ; 
for size 8' X 8' X 8' $194.65 to $224.72. 



LAW OF B. & S. GAVCIE. 

The absence of a wire table may often be compensated for by remember- 
ing the following approximate facts concerning the B. & S. gauge. 

Diameter of No. 10 wire = .1 inch. 
Resistance of No. 10 per 1000 feet = 1 ohm. 
Weight of No. 10 per 1000 feet = 31.37 lbs. 

Diameters are halved for every six units increase' in gauge No.; i.e., No. 16 
has half the diameter of No. 10, and No. 4 has twice the diameter of No. 10. 
Accordingly cross-sectional areas double at every decrease of three in the 
gauge number. 

The gauge numbers correspond to cross-sections and conductivities which 
vary as an inverse geometrical progression having a ratio of 1 .26. 



204 



PROPERTIES OF CONDUCTORS. 



FUSjOTG EfJFECTS Of ELECTRIC C'l'linKXTK. 

By W. H. Preece, F. R. S. See " Proc. Roy. Soc.," vol. xliv., March 15, 1888. 

The Law — 1 = ad 2 , where /, current ; a, constant ; and d, diameter — 
is strictly followed; and the following are the final values of the constant 
"a," for the different metals us determined by Mr. Preece : — 

Inches. Centimeters. Millimeters. 

Copper 10,244 2,530 80.0 

Aluminum .... 7,585 1,873 59.2 

Platinum 5,172 1,277 40.4 

German Silver. . . . 5,230 1,292 40.8 

Platinoid 4,750 1,173 37.1 

Iron 3,148 777.4 24.6 

Tin 1,642 405.5 12.8 

Alloy (lead and tin 2 to 1) 1,318 325.5 10.3 

Lead 1,379 340.6 10.8 



Table Giving* the Diameters of Wires of Various materi- 
als Which Will Be fused l*y a Current of Given 





Strength. — W 


H. Preece, F. R 


S. d= 


®* 














Diameter in Inches. 








& 

02 


4 




eg 


IS 


•So 

■se 


00 


1 


111 


OS 

g 


r ■—' 


PnrH 


S 


s l0 


02"^ 


£** 


CO 




0> g 




o*4 


1" 


2 11 
3 e 


i 11 


u\\ 


in 

S 8 


n 

M 




SJ3 


In 


l 


0.0021 


0.0026 


0.0033 


0.0033 


0.0035 


0.0047 


0.0072 


0.0083 


0.0081 


2 


0.0034 


0.0041 


0.0053 


0.0053 


0.0056 


0.(XF4 


0.0113 


0.0132 


0.0128 


3 


0.0044 


0.0054 


0.0070 


0.0069 


0.0074 


0.0097 


0.0149 


0.0173 


0.0168 


4 


0.0053 


0.0065 


0.0084 


0.0084 


0.0089 


0.0117 


0.0181 


0.0210 


0.0203 


5 


0.0062 


0.0076 


0-0098 


0.0097 


0.0104 


0.0136 


0.0210 


0.0243 


0.0236 


10 


0.0098 


0.0120 


0.0155 


0.0154 


0.0164 


0.0216 


0.0334 


0.0386 


0.0375 


15 


0.0129 


0.0158 


0.0203 


0.0202 


0.0215 


0.0283 


0.0437 


0.0506 


0.0491 


20 


0.0156 


0.0191 


0.02*6 


0.0245 


0.0261 


0.0343 


0.0529 


0.0613 


0.0595 


25 


0.0181 


0.0222 


0.0286 


0.0284 


0.0303 


0.0398 


0.0614 


0.0711 


C.0690 


30 


0.0205 


0.0250 


0.0323 


0.0320 


0.0342 


0.0450 


0.0694 


0.0803 


C.0779 


35 


0.0227 


0.0277 


0.0358 


0.0356 


0.0379 


0.0498 


0.0769 


0.0890 


0.0864 


40 


0.0248 


0.0303 


0.0391 


0.0388 


0.0414 


0.0545 


0.0840 


0.0973 


0.0944 


45 


0.0268 


0.0328 


0.0423 


0.0420 


0.0448 


0.0589 


0.0909 


0.1052 


0.1021 


50 


0.0288 


0.03o2 


0.0454 


0.0450 


0.0480 


0.0632 


0.0975 


0.1129 


0.1095 


60 


0.0325 


0.0397 


0.0513 


0.0509 


0.0542 


0.0714 


0.1101 


0.1275 


0.1237 


70 


0.0360 


0.0^40 


0.0568 


0.0564 


0.0601 


0.0791 


0.1220 


0.1413 


C..1371 


80 


0.0394 


0.0481 


0.0621 


0.0616 


0.0657 


0.0864 


0.1334 


0.1544 


0.1499 


90 


0.0426 


0.0520 


0.0672 


0.0667 


0.0711 


0.0935 


0.1443 


0.1671 


0.1621 


100 


0.0457 


0.0558 


0.0720 


0.0715 


0.0702 


0.1003 


0.154S 


0.1792 


0.1739 


120 


0.0516 


0.0630 


0.0814 


0.0808 


0.0801 


0.1133 


0.1748 


0.2024 


0.1964 


140 


0.0572 


0.0698 


0.0902 


0.0895 


0.0954 


0.1255 


0.1937 


0.2243 


0.2176 


160 


0.0625 


0.0763 


0.0986 


0.0978 


0.1043 


0.1372 


0.2118 


0.2452 


0.2379 


180 


0.0676 


0.0826 


0.1066 


0.1058 


0.1128 


0.1484 


0.2291 


0.2652 


0.2573 


200 


0.0725 


0.0886 


0.1144 


0.1135 


0.1210 


0.1592 


0.2457 


0.2845 


0.2760 


225 


0.0784 


0.0958 


0.1237 


0.1228 


0.1309 


0.1722 


0.2658 


0.3077 


0.2986 


250 


0.0841 


0.1028 


0.1327 


0.1317 


0.1404 


0.1848 


0.2851 


0.3301 


0.3203 


275 


0.0897 


0.1095 


0.1414 


0.1404 


0.1497 


0.1969 


0.3038 


0.3518 


0.3413 


300 


0.0950 


0.1161 


0.1498 


0.1487 


0.1586 


0.2086 


0.3220 


0.3728 


0.3617 



TABLES OF LENGTHS AND STRAINS. 



205 



TABLJES OF 1EX«TH» ASW §TRAOi IN SPANS 
OF WIMli AND ISVSPEMIOIV CARIES. 

By John A. Roebling's Son's Co. 

The formulae used in calculating these tables of lengths and strains in 
spans of wire are those of a catenary of small deflection. They are given 
in Weisbach's " Mechanics of Engineering," page 297 (seventh American 
edition, translated by Eckley B. Coxe, A. M.). 

In these tables the horizontal strain at the centre of the span is given. 
The strain at any other point equals the strain at the centre plus the weight 
of a length of the wire equal to the perpendicular distance of that point 
from the lowest point of the wire in the span. For ordinary spans this is 
negligible. For any given wire the longest possible span is one where the 
deflection is about one-third of the span. 

The effects of temperature on the strains of wires in spans is at first sight 
so great as to render the other considerations of little importance. The 
table, page 209, is calculated on the assumption that the supports of tbe 
spans are perfectly rigid under all conditions of strain, and that the wire is 
inelastic. This is never true in practice. The changes in direction in a 
pole line afford a chance for the strains, due to a shortening of the wire by 
a fall in temperature, to be taken up by a bending of the supports. 

If the elastic limit of hard-drawn copper wire of 60,000 pounds breaking 
strain be taken at 20,000 pounds, then S will equal 20,000 divided by 3.85, the 
weight of a piece of copper one foot long and one square inch in section. 
This makes S equal 5.195. Looking at the table of values of S, page 218, 
this value for a span of 130 feet comes between a deflection of .003 and .004. 
In the same way the allowable deflection for any other span of hard-drawn 
copper could be found, or for any other material, by substituting the proper 
terms for the elastic limit and the weight per foot given above. Some of 
the tables give data for telegraph wire, poles for which are spaced by the 
number per mile, while other tables are for conductors on poles spaced by 
the foot, such as electric light and poAver lines. 

Actual deflection of wires of all construction depends much on the judg- 
ment of the linemen and the tools at hand. 

The following gives the practice of some of the telegraph and telephone 
companies in their line construction : 



SPECIFICATIONS FOR STANDARD CONSTRUC- 
TION OF HARD-DRAWN COPPER. 









Spans in feet. 






<D co +i 












£ <£•£ 












323 














* iS 


75 


100 


115 


130 


150 


200 
































Sag in inches. 


—30 


1 


2 


2i 


3| 


U 


8 


—10 


11 


2£ 


3 


3| 


5 


9 


10 


n 


24 


3* 


4| 


5| 


101 


30 


if 


3 


4 


5i 


61 


12 


60 


2* 


4i 


5i 


7 


9 


15f 


80 


3i 


5§ 


7 


8f 


iH 


18| 


100 


H 


7 


9 


11 


14 


22i 



206 PROPERTIES OF CONDUCTORS. 



For spans between 400 and 600 feet, the dip shall be l^lOth of the span. 

For spans between 600 and 1000 feet, the dip shall be l-30th of the span. 

Another company uses 40 poles to the mile, and in the East allows three- 
inch dip at centre of spans. In the West, where the variation of tempera- 
ture is greater, 10 inches dip is allowed in summer, and 8 inches in the 
winter. This construction applies to both copper and iron wire, and has 
been found by actual experience to give satisfactory results : 

The following formulae were used in calculating the tables : 

(1) S X w — horizontal strain on wire at centre of span. 



(2) B=t + 



(3) 
(4) 



[*+«(D1- 



x = 3S-**S 2 - 



(5) x - Zyl-Zy' 



r- 



In these formulae 

y = one-half span. 
I = one-half length of wire in span. 
x = deflection at centre in same units as y. 
w = weight per foot of wire. 
Suppose we have a span of 200 feet of hard-drawn copper wire weighing 
one pound to 10 feet, and a deflection of two feet or .01 of the span. 





= 2500.33 +. 


(3) 


<= 100 [ l + *{£»)!■ 




= 100.026 6 +. 




21 = 200.053 -f. 


(4) 


x = 7501 — V56,205,001 — 30,000. 


(5) 


x — /30,008 — 30.006. 



In calculating the table, page 209, the deflection of the line was determined 
at — 10° F. by formula 4, the value of S being 30,000 divided by 3.85 or 7,792. 
For the other temperatures the length of the wire was calculated from the 
following formula : 

Length =1(1 + .000009 3 t ) 
Here t is the difference in temperature in degrees Fahrenheit. 
By formula 5 the deflection corresponding to the new length was found. 
The coefficients of linear expansion for each degree Fahrenheit are as 
follows : 

Copper, .000 009 3. 
Iron, .000 006 8. 
Lead, .000 016. 



TEMPERATURE EFFECTS. 207 

TEMPERATURE EEJPECTS Il¥ SPAITS. 







Temperature in 


degrees 


Fahrenheit. 






PR 


















.s 

as 


—10° 


30° 


40° 


50° 


60° 


70° 


80° 


90° 


100° 


s8 


Deflections in inches. 


50 


.5 


6 


8 


9 


9 


10 


11 


11 


12 


60 


,7 


8 


10 


11 


11 


12 


13 


13 


14 


70 


1. 


10 


11 


12 


13 


14 


15 


15 


17 


80 


1.2 


11 


13 


14 


15 


16 


17 


18 


19 


90 


1.6 


13 


14 


16 


17 


18 


19 


20 


21 


100 


1.9 


14 


16 


17 


19 


20 


21 


23 


24 


110 


2.3 


16 


18 


19 


21 


22 


24 


25 


26 


120 


2.8 


17 


19 


21 


22 


24 


26 


27 


28 


130 


3.2 


19 


21 


23 


25 


26 


28 


29 


31 


140 


3.7 


20 


23 


25 


27 


28 


30 


32 


33 


150 


4.3 


22 


24 


26 


28 


30 


32 


34 


36 


160 


4.9 


23 


26 


28 


30 


32 


34 


36 


38 


170 


5.5 


25 


28 


30 


32 


35 


37 


38 


40 


180 


6.2 


26 


29 


32 


34 


37 


39 


41 


43 


190 


7. 


28 


31 


34 


36 


39 


41 


43 


45 


200 


7.7 


31 


33 


36 


38 


41 


43 


45 


48 



Hard-drawn copper wire, 60,000 pounds strength per square inch. 

Strain at — 10° F., 30,000 pounds per square inch. 

The following tables give the dip in feet and inches of No. B. & S. cop- 
per trolley wire between spans 125' apart, and the strain in pounds for vari- 
ous temperatures : 

Initial Maximum Strain 2000 Ebs. 



Temperature F. 


Dip. 


Strain. 




—10° 


3.7" 


2000 lbs. 




0° 


9.7" 


774 " 




32° 


V 6" 


415 " 




50° 


V 10" 


340 " 




70° 


2' 1" 


300 " 




90° 


2 / 4// 


267 " 




10° 


3.7" 


2000 " 




32° 


V 2" 


534 " 




50° 


V 6" 


415 " 




70° 


V 10" 


340 " 




90° 


2 / 1" 


300 » 




32° 


3.7" 


2000 " 




50° 


V 


623 " 




7<r 


V 5" 


440 " 




90° 


V 10" 


340 " 





From the preceding tables the proper height of eyebolts can be deter- 
mined for various spans and temperatures with a given minimum height of 
trolley wire above the track. 



208 



PROPERTIES OF CONDUCTORS. 



Sag's and Tensions for Suspended Wires. 

The tension when the temperature is lowest, i.e., when the strain is great- 
est, should not exceed one-fourtb of the breaking strain. 

The sag varies with the material, but not with the gauge; the tension 
varies directly with the weight per foot of the wire. 






d= v*^- 



8d 2 



Pw 



i);L= ; + ^ (=lt 



where 



also, 



and 



I = span ; 

w = weight of imit length ; 

d = sag (or dip) ; 

L = length of wire in span ; 

t = tension; 

w for 400-lbs. Iron = .075758 lb. per foot. 
" 150 " Coppers .028409 " " 

» 100 " " = .018939 " " 



Coefficient of expansion for iron = .00000683 per deg. F. 
Coefficient of expansion for copper = .00000956 " " 

TABLE Of TJEWSIIiE STRENGTH FOR COPPER 
WIMJE. 





«m 






«H 




02 


O 


o 


02 


O 


o 


<9 


^ - 


2 


«8 


[Sio^ 


2 


PQ . 


bJ0£ 


.»d 


B 


.5NS 




£5 


0> 


it' 




© 0) 

1" <» 


u 


bib-} 


bJDg 


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tlC-rJ 


bJO^ 


o 


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CO M 
? 




O 


■3 m 


u 


go 


w 


PQ 


CZ2 


pq 


W 




Lbs. 


Lbs. 




Lbs. 


i&s. 


0000 


9971 


5650 


9 


617 


349 


000 


7907 


4480 


10 


489 


277 


00 


6271 


3553 


11 


388 


219 





4973 


2818 


12 


307 


174 


1 


3943 


2234 


13 


244 


138 


2 


3127 


1772 


14 


193 


109 


3 


2480 


1405 


15 


153 


87 


4 


1967 


1114 


16 


133 


69 


g 


1559 


883 


17 


97 


55 


6 


1237 


700 


18 


77 


43 


7 


980 


555 


19 


61 


34 


8 


778 


440 


20 


48 


27 



i 



LENGTH OE WIRE AND DEFLECTION. 



209 



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210 



PROPERTIES OF CONDUCTORS. 



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LENGTH OF WIRE AND DEFLECTION. 



211 



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TABLE OF STRAINS AT CENTRE OF SPANS. 



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BREAKING WEIGHTS. 219 



Notes. 

Comparative Resistance of Woods (Addenbrooke). The 
measurements were made along the grain by inserting terminals two inches 
apart in sound, dry, well-seasoned pieces of the woods, each piece being 
3" X \" X f". Other tests across the grain gave results from 50 to 100 per 
cent higher. 

Wood. Megohms. Wood. Megohms. 

Mahogany ... 48 Lignum Vitae . 397 

Pine . ... 214 Walnut . . . ! 478 

Eosewood . . . 291 Teak 734 

BREAKING WEIGHTS COPPER AXII SILICON 
BROUfZE WIRES. 

Breaking weight hard-drawn copper wire per 1000 C. M. == 47.12 lbs. 

Breaking weight soft-drawn or annealed copper wire per 1000 C. M. = 
26.69 lbs. 

Breaking weight No. 0B. & S. hard-drawn copper wire = 4973 lbs. 

Breaking weight No. 0B. & S. soft-drawn or annealed copper wire =: 
2817 lbs. 

Breaking weight silicon bronze wire per square inch, 80920 lbs. 

Breaking weight No. 4 B. W. G. silicon bronze wire, 3600 lbs. 

Horse-power lost in copper conductor at a density of 1000 amperes per 
square inch cross section, is equal to the number of thousands of cubic 
inches of copper -f- 10%. 

— By Prof. G. Forbes, 



DIMEKilOli OF CROSS ARMS. 

Regular size, 3J inches X 4^ inches, U-inch holes. 

Special size, 4 inches X 5 inches, l£-inch holes. 

2-pin, 3 feet long ; 4-pin, 4 or 5 feet long ; 6-pin, 6 feet long. 



CABLE TESTING. 

CABLE**. 
Cables — Underground and Submarine. 

The majority of the methods of tests and measurements given herein are 
applicable to aerial, underground, and submarine cables. 

Insulation Resistance. 

Direct Deflection Method, with Mirror Galvanometer. — 

This method, Fig. 1, is generally used in this country in underground and 
submarine work. 




vXXXNNSNXVVVVVVVVs 



I Fig. 1. 

a and b = leads. 

G = galvanometer, Thomson or D'Arsonval, mirror type. 
S= shunts for G, usually &, T Jjj, xn J 0n . 
B = battery, 20, 50, or 100 chloride silver cells. 
E = resistance box of 100,000 ohms. 
BK = battery reversing key. 
SK = short-circuit key for G. 
First connect a to lower contact point of SK, and take constant of G, 
using y^oo shunt, and small number of cells, say 5 (depending upon the sen- 
sitiveness of G), with standard resistance B only in circuit, b being discon- 
nected as shown. If 5 cells are used in taking constant, and 100 cells are 
to be used for test, 

G deflec. x shunt x R X 20 

Constant .-= i^o^OOO = me g° hms - 

After obtaining the constant, measure insulation resistance of lead b, by 
joining it to SK instead of a, disconnecting the far end of b from the cells. 
The result should be infinity ; but if not, deduct this deflection from the 
deflection to be obtained in testing the cable proper. Now connect the far 
end of b to the conductor of the cable, the far terminal of latter being free. 
Then open SK carefully, and observe if there are any earth currents from 
the cable. If any, note deflection due to the same, and deduct from bat- 
tery reading if in the same direction, or add to it if in opposite direction. 
Short-circuit G with SK, and close one knob of BK, using, say, the r J ff shunt. 
After a few seconds open SK ; if spot goes off the scale, use a higher shunt. 
If deflection is low, use a lower shunt. After one minute's electrification, 
note the deflection. Tbe result may be worked out from this reading, but 
the current should be kept on for three or five minutes longer, and readings 
taken at end of each minute. The deflection should decrease gradually. 
At the end of the last minute of test, open BK, and allow the cable to 

220 



CABLE TESTING. 



221 



discharge fully. Then close SK and press the other knoh of BK, revers- 
ing the battery. After a few moments, open SK, and take readings of deflec- 
tions as before. 



The insulation resistance in megohms 



constant 
d X S ' 



where d is the deflection at a given time, and S is the shunt used. 

. . , constant 
shunt is used, x = = • \ 



If no 



Note that in the above constant, the ordinary constant is multiplied by 20 
for the reason that the battery is increased 20-fold, or 5 : : 100, In case the 
same battery is used for testing as for obtaining the constant, then 



constant : 



G deflec. X S X R 
1,000,000 



If there be ho earth currents, the readings with opposite poles of battery 
to the cable should not vary appreciably at any given minute. Pronounced 
variation between the readings at given times and unsteady deflection indi- 
cate defective cable. 

Insulation Resistance l»y Method of Loss of Charg-e. 

The insulation resistance of a cable or other conductor having considera- 
ble capacity may be measured by its loss of charge. Let one end of the 
conductor be insulated, and the other end attached to an electrometer, in 
the manner shown in FlG. 2. 




Fig. 2. 

Let JR =z Insulation resistance in megohms per mile. 
C = Capacity in microfarads per mile. 
E =: potential of cable as charged. 
e = potential of cable after a certain time. 
Depress one knob of key K, and throw key K' to the right, and charge the 
cable for one minute ; then throw key K' to the left, thus connecting the 
cable to the electrometer. Note the deflection E. Noting the movement of 
the spot for one minute, take reading e at end of minute, then 



R = 



26.06 
Clog^ 



If an electrometer is not conveniently at hand, use a reflecting galvanom- 
eter, and after charging cable as before, take an instantaneous discharge, 
noting deflection E due thereto. Recharge cable as before, then open K' 
and at end of one minute, the galvanometer having been disconnected from 
cable in the meantime, take another discharge-reading of cable e, and apply 
the same formula as before. If a condenser of low capacity be inserted be- 
tween K' and the galvanometer, the latter need not be disconnected. The 
advantage of the use of the electrometer is that the actual loss of potential 
of the cable may be observed as it progresses. 



222 



CABLES. 



Testing- Joints of Cables by Clark's method. 

In the figure (Fig. 3) the letters refer to the parts as follows : 




O is a high-resistance mirror galvanometer. 

S is the shunt. 

K, is the short-circuit key. It may be on the shunt box or separate. 

A' /7 is a reversing key. 

K IU is a discharge key. • 

B the battery, usually 100 cells chloride of silver. 

C is a J microfarad standard condenser. 

The joint to be tested is placed in a well-insulated trough, nearly filled 
with salt water. A copper plate attached to the lead wire is placed in the 
water to ensure a good connection with the liquid. The connections are 
made as shown in the figure, one end of the cable being free. To make test 
close K nl for a half minute; then release it (first depressing one knob of 
key A,,), thereby discharging the condenser C, through the galvanometer, 
and note the deflection, if any. A perfect piece of cable of the same length 
as the joint is then placed in the vessel, and if the results with the joint are 
practically equal to those obtained with the perfect cable, the joint is passed. 
When the deflection is very low, it is evident that the joint is sound, and it 
may then be considered unnecessary to compare it with the piece of cable. 
It is very important that the trough and apparatus be thoroughly insulated. 

Electrometer Method. — This method possesses the advantage that 
it dispenses with a condenser, and thereby avoids possible misleading re- 
sults due to electric absorption by that instrument. The connections for 
the electrometer test are shown in the accompanying figure (Fig. 4). 




ELECTROMETER 



Fig. 4. 

B is a battery of about 10 cells. 

B, is a battery of 100 or more cells. 

As in the preceding test, it is here highly essential that the insulation of 
the trough should be practically perfect, or at least known, so that if not 
perfect, proper deductions may be made for deflections due to it alone. 

To test the insulation of the trough, depress A,, and close switch S. This 



CABLE TESTING. 



223 



charges the quadrants of the electrometer, and produces a steady deflection 
of its needle, and shows the potential due to the small hattery B. Now 
open switch S, still keeping K, closed, and watch the deflection of needle 
for about two minutes. If the insulation of the trough is not perfect, there 
will be a circuit, so to speak, from the earth at the trough to the earth 
shown in the figure, and a fall in the deflection will be the result. If, how- 
ever, the drop of potential is not more than is indicated by a fall of two or 
three divisions, the insulation of the trough will suffice. The electrometer 
is discharged by closing switch S, which short-circuits the quadrants, K, 
being open at this time. The joint is now connected as in the figure. 
Switch S is opened, and key K n depressed, thus charging the joint with the 
large battery i?,. This produces a quick throw of the needle, due to the 
charging of the joint. Next, keeping K tl closed, discharge the electrometer 
by closing switch S for a moment. The switch is then opened, and if the 
joint is imperfect as to its insulation, the deflection will rise as the elec- 
tricity accumulates in the trough. The deflections are recorded after one 
and two minutes, and are compared, as in the previous test, with a piece of 
perfect cable. The results obtained with the joint should not greatly ex- 
ceed those of the cable proper. 

Direct Deflection Mtethod. — The insulation resistance of joints 
may also be tested by the direct deflection method already described, and 
when great accuracy is not required, is preferable, owing to its simplicity. 

Capacity. 

Capacity tests are usually made by the aid of standard condensers. Con- 
densers, or sections of the plates of condensers, may be arranged in parallel 
or in series (cascade). 

Arrangement of Condensers — Parallel. — Join like terminals 
of the condensers together, as in the figure ; then the joint capacity of the 
condensers is equal to the sum of the respective capacities. 

Capacity, C= C + C, + C„ + C /y/ . 



1111 



C/ 



Fig. 5. 
Condensers in Series or Cascade. — Join the terminals, as in 
Fig. 6. The total capacity of the condensers as thus arranged is equal to 
the reciprocal of the sum of the reciprocals of the several capacities, or 

1 

Capacity in series =: 1 , 1 1 , 1 



Mg§7 



Fig. 6. 
Condensers are now constructed so that these two methods of arranging 
the plates of a condenser may conveniently be combined in one condenser, 
thereby obtaining a much wider range of capacities. 



224 



CABLES. 



Testing* Capacity l>y Direct Discharge. — It is frequently de- 
sirable to know the capacity of a condenser, a wire, or a cable. This may 
be ascertained by the aid of a standard condenser, a trigger key, and • an 
astatic or ballistic galvanometer. First, obtain a constant. This is done by 
noting the deflection d, due to the discharge of the standard condenser after 
a charge of, say, 10 seconds from a given E.M.F. Then discharge the other 
condenser, wire, or cable through the galvanometer after 10 seconds charge, 
and note the deflection d'. The capacity c' of the latter is then 

d, 
C < = G d> 
c being the capacity of the standard condenser. 

Capacity H>y Thomson's Method. — This method is used with 
accurate results in testing the capacity of long cables. In the figure (Fig. 7) 



•R/ 



B-^^_ EARTH | 



1 



Fig. 7. 



B =r battery, say 10 chloride silver cells. 

R = adjustable resistance. 

/?,=r fixed resistance. 

G = galvanometer. 

C =z standard condenser. 

1, 2, 3, 4,5, keys. 

To test, close key 1, thus connecting the battery B, thvough the resist- 
ances R, R„ to earth. Then 

V: V,::R:R, 
where V and V / ■=. the potentials at the junctions of the battery with R R,. 

Next close keys 2 and 3 simultaneously for, say 5 minutes, thereby char- 
ging the condenser to potential V, and the cable to potential V, 

Let Cbe the capacity in microfarads of the condenser, and U, capacity of 
cable, and let Q and Q, be their respective charges when the keys were 
closed. Then Q : Q, :: VC : V,C r 

Open keys 2 and 3, keeping key 1 closed for say 10 seconds, to allow the 
charges of cable and condenser to mix or neutralize, in which case, if the 
charges are equal, there will be no deflection of the galvanometer when key 
5 is closed. If there is a deflection, it is due to a preponderance of charge 
in Cor C r Change the ratio of R to R n until no deflection occurs. 

Then, VC— V, C, 

or V : V :: C : C . 

But we found V, : V : : R, : R 

or R, : R :: C : C r 

and Cyz= ~ C microfarads. 

Testing- Capacities I»y lord Kelvin"* Dead-Beat, Multi- 
cellular Voltmeter. — Suitable for short lengths of cable. 
M!'= multicellular voltmeter. 
A('= air condenser. 



CABLE TESTING. 



225 



I? — battery. 

S = switch. 

Q = total charge in condenser and M V, due to battery. 
Ca = capacity of AC. 
Cb =r capacity of cable. 




Fig. 8. 

First close switch S on upper point 1, and charge MV&nd AC to a desired 
potential, V. Next move switch S from point 1 to lower point 2, and note 
the potential V, at MV. 

Then Q = V (C + Ca) = V,{C-\- Ca+ Cb), where Cis the capacity of volt- 
meter. Ordinarily C can be neglected, as compared with the capacities of 
vlC and the cable, in which case, by transposition, 

Cb=(V—V / ) Ca+ V,. 

Conductors of telephone cables are measured for capacity with the lead 
sheathing or armor and all condiictors but the one under test grounded. 

locating- Crosses in Cables or Aerial "Wires.— I*rof. Ayr- 
ton JHet liotl. — To locate the cross at d (Fig. 9) arrange the connections 



-TjiTJnr 




Fig. 9. 
as shown. This is virtually a Wheatstone bridge, in which one of the wires, 
n, is one of the arms of same. Adjust r until a (x + y) = br, when r will be 
equal to x + y, if a = b. 




Fig. 10. 



226 CABLES. 

Next connect the battery to line m instead of to earth, as in Fig. 10, and 
adjust a until ax = by. 

r^ X b 

Then p— = 1 — = — 

and as x -f- y = r in the first arrangement, 

v b x r 

hence, x = ^-—. — • 

b -{- a 

This test may be varied by transposing G and the battery, in Fig. 9, which 
is the old method of making this test. 

locating* faults in Aerial Wires or Catties \*y the loop 

Test. — Two conductors are necessary for this test, or both ends of a cable 
must be available at the testing-point. Also it is assumed there is but one 
defect in the conductor. The resistance of the fault itself is negligible in 
this test. 

Measure the resistance L of the loop by the ordinary Wheatstone bridge, 
— Murray's Iflethod. Connect as in Fig. 11, in which a and b are the 
arms of a Wheatstone bridge, and y x are resistances to fault, the conduc- 
tors being joined at J" (in the case of aerial wire, for instance). Close key 
and note the deflection of needle due to earth current, if any. This is called, 
the false zero. 




Fig. 11. 

Now apply the positive or negative pole of tbe battery, by depressing one 
of the knobs of reversing key K, and balance to the false zero previously 
obtained by varying the resistance in arms a or b. Then, by Wheatstone 
bridge formula, 

ax = by, 
and I = x -f- y 

y= I —x 

X=Z a-T-b l 

a I. 



u ~ a + b 

To ascertain distance in knots or miles from 2 to F, divide x by resistance 
per knot or mile ; to ascertain distance from 1 to F, divide y by resistance 
per knot or mile. 

The foregoing test is varied in the case of comparatively short lengths of 
cable, in the manner shown in Fig. 12, in which the positions of the battery 
and galvanometer are transposed. Otherwise the test and formula are the 
same. It is advisable to reverse the connections of cable or conductors at 2 
and 1, and take the average of results obtained in the different positions. 
In this latter method, battery B should be of low resistance, and well insu- 
lated. 

Best conditions for making test, according to Kempe. — Resistance of b 
should be as high as necessary to give required range of adjustment in a. 



CABLE TESTING. 



227 



Resistance of galvanometer should not be more than about five times the 
resistance of the loop. 




Fig. 12. 

"Varley Loop Test. — Measure resistance of looped cable or conduc- 
tors as before. Then connect, as shown in Fig. 13, in which r is an adjustable 
resistance. Obtain false zero as before. Then close key K, and adjust r for 
balance. In testing, when earth current is present, the best results are 
obtained when the fault is cleared by the negative pole, and just before it 
begins to polarize. 




Fig. 13. 



Then 



L — r 



where x is the distance of fault, in ohms, from point 2 of cable proper. 

Then x -£- by the resistance of the cable or conductor per knot or mile 
gives the distance of fault in knots or miles. 

Locating- faults in Insulated "Wires. — The following, so to 
speak, "rule of thumb," or point to point electro-mechanical methods of 
locating faults in unarmored cables, in which the defect is not a pronounced 
one, have been found successful. 

Warren's Method. — The cable should be coiled on two insulated 
drums, one-half on each drum. The surface of the cable between the drums 
is carefully dried. One end of the conductor is connected to a battery which 
is grounded. The other terminal is connected to the insulated quadrants 
of an electrometer, the other pairs of quadrants of which are connected to 
the earth. Both drums being well insulated, no loss of potential is observed 
after three or four minutes. An earth wire is now connected first to one 
and then another of the drums, and the fault will be found on the drum 
which shows the greater fall on the electrometer. The coil is now uncoiled 
from the defective drum to the other drum, and tests are made at intervals 
until the defect is found. 



228 CABLES. 



V, Jacob coils the core from a tank to a drum. The battery is con- 
nected between the tank and the conductor, one end of which is free. A 
galvanometer is joined between the tank and drum, which need only be 
partially insulated. The needle shows when the fault has passed to the 
drum, and it can be localized by running the galvanometer lead along the 
insulated wire. 

Insulating- Cable Ends for Tests. — Much care must be exer- 
cised in order to insure accurate results in testing for insulation resistance. 
The ends should be well cleaned and thoroughly dry. The ends are for this 
purpose sometimes immersed in boiling paraffin wax for a few seconds ; at 
other times they may be dried by the careful application of heat from a 
spirit lamp. 

Copper Resistance, or Conductivity of Cables. 

The copper resistance of the submarine and underground cables used in 
telephony and telegraphy is always tested at the factory, usually by the 
Wheatstone bridge method. In such a case both ends of the cable are ac- 
cessible. When the cable is laid, if the far end is well grounded, the cop- 
per resistance may be measured, either by the Wheatstone bridge method, 
or by a substitution method, as follows. First, note the deflection due to 
copper resistance of conductor. Then substitute an adjustable resistance 
box and vary the resistance in the box until the deflection equals that due 
to cable. This latter resistance is the resistance of the cable. If there are 
earth currents on the cable, take readings of cable resistance with each 
pole of battery. Should there be any difference between the results ob- 
tained with the respective poles of the battery, the actual resistance will, 
according to F. Jacob, be equal to the harmonic mean of the two results, i.e., 

„ 2 rr' 

r-f- r' 
where E is the actual resistance, r is the resistance with -4- pole, r' is the 
resistance with — pole. 

Testing- Submarine Cable [During- Manufacture and 
laying. 

Tbe Core of the cable, that is, the insulated copper conductor, is 
made, as a rule, in lengths of 2 knots, which are coiled upon wooden drums, 
and are then immersed in water at a temperature of 75° F. for about 24 
hours. The coils are then tested for copper resistance, insulation resis- 
tance, and capacity ; the results of which tests, together with data as to 
length of coils, Aveight, etc., are entered on suitably prepared blanks. 

After the tests of some of the coils have been made, the jointing up of 
the cable begins, which is followed by the sheathing or armoring. The 
joints are tested after 24 hours immersion in water. During the sheathing 
process, continuous galvanometer or electrometer tests are made of the 
core, to see that no injury befalls the cable during this process. In fact, 
practically continuous tests of the cable for insulation resistance, copper 
resistance, and capacity should be made until the laying of the cable begins. 

During laying, the cable should be tested continuously, and communica- 
tion should be practically constant between the ship and the shore. An 
arrangement to permit such tests and communication is shown in Fig. 14. 



SHIP n 

B e l 




Fig. 14o 



CABLE TESTING. 229 



In this figure, G, is a marine galvanometer, B is a battery of about 100 
cells on ship-board. In the shore station, L is a lever of key K, C is a con- 
denser, G 2 is a galvanometer. Normally key K is open and the cable is 
charged by battery B, If, while the cable is being paid out a defect occurs 
in the insulation, or if the conductor breaks, a noticeable throw of the galva- 
nometer follows, and the ship should be stopped and the cause ascertained. 
By pre-arrangement the lever of shore key K is closed, say every 5 minutes, 
thereby charging the condenser C, which causes a throw of the galvanom- 
eters' needles. If the ship or shore fails to get these periodic signals, or 
if they vary as to their strength, it indicates the occurrence of a defect. 
At the end of every hour the ship reverses the battery, which reverses the 
direction of the deflection of the galvanometers. If the ship desires to 
communicate with the shore, the battery is not reversed at the hour, or it 
is reversed before the hour. If the shore wishes to speak with the ship, the 
key K is opened and closed several times in succession. In either event, 
both connect in their regular telegraphing apparatus for conversation. 

Compound Cables, that is, cables of more than one conductor, have 
their conductoi-s connected in series for these tests. If there is an even 
number of conductors, two of them must be connected in parallel. 



DYNAMOS. 

CONTINUOUS cumment machiies. 

Electro Motive JForce. 

The E.M.F. of a dynamo depends upon, 

a, The speed of revolution of the armature, 

b, The number of conductors on the armature, 

c, The method of connecting same, 

d, The total flux or lines of force forced through the armature core by the 
field magnets. 

If the above four items be expressed in C.G.S. measure, the absolute 
E.M.F. will be expressed in the same units, which can be changed to volts 
by dividing by 100,000,000 or 10 8 . Then for a two-pole dynamo, 

Let rev — revolutions of armature per second, 

n =z number of external conductors all around the armature, 

$ = the total flux passing through the armature core from pole to 

pole, 
E = total E.M.F. generated by the machine, 

V= E.M.F. at machine terminals = E — rlwkererl = volts drop or 
loss in the machine itself. 

Then 

and 



108 

Ex io 8 



rev. x n 
For multipolar dynamos, in addition to the above symbols, 

let p — number of pairs of poles, 

<$>, = flux from one pole, 

then in a Series wound multipolar dynamo ; 

„ rev. xj)X»iX*/ 

E = w~ 

, £ x io 8 

and $, = 



rev. xp X n 
In a Multiple wound multipolar dynamo, • 

_ rev. x n x $, 



and $/ 



IO 8 
E x 10 8 



ALTERNATING ClTHMJUfT MACHOEfi. 

For alternating or periodically varying currents there are three values of 
the E.M.F. used, or of which the value is required : 

a, The maximum value, or the top of the wave, 

b, The instantaneous value of a point in the wave, 

c, the virtual E.M.F., or Vmean 2 value of the full wave. 

230 



ALTERNATING CURRENT MACHINES. 231 

In addition to the symbols used for continuous currents, let 

k= a constant varying from 1.1 to 2.5 depending on the relative widths of 
the armature coils and pole-pieces, usually taken as 2.22. 

= angle through which the armature coil is turned at the instant 
taken. 

Then, for single-phase alternators, 

_, 2tt X n X $/ X rev. x p 

maximum E ■= r^ — 

10 8 

In this case n = number turns in series, and $ = maximum flux enclosed 
per turn, 

E max. x 10 8 



and $, = 

Instantaneous E — 



'In xnx rev. X p 

2tt x n X */ X rev. xpX s» 
i0» 



In this case n = number turns in series, and $ = maximum flux enclosed 
per turn, 

and *, = : Einst.xW 

Virtual E = reV ' X P X J X *< X n 

In this case n = number of conductors joined in series with one another 
around the armature, 

E vir. x 10 8 
and - 



' rev. x p X k x n 
For multiphase alternators 

n ■=. the number of conductors in series in a phase, and in two-phase ma- 
chines the E.M.F.'s of each phase would be the same as in a single-phase 
dynamo. 

In three-phase alternators the E.M.F. between terminals will depend upon 
the method of connecting the armature conductors. The two most common 
methods are called the delta connection and the Y or star connection, both 
shown in the following diagrams. 




ir 







DELTA CONNECTION Y OR STAR CONNECTION 

Figs. 1 and 2. Values of E.M.F. in three-phase connections when x = y = z. 

In the delta- connected armature the E.M.F.'s between terminals are those 
generated in each coil, as shown in the diagram. 

In the Y-connected armature the E.M.F. between any two terminals is 
the E.M.F. generated by one of the coils in that phase multiplied by the "^3 
or 1.732. 

Two-phase circuits are sometimes connected as a three-phase circuit ; that 
is, both phases have a common return wire. In this case the pressure be- 
tween the two outgoing wires is V<j x E, and the current in the common 
return will be I V2, both conditions are on the assumption that E and i" in 
each phase is the same. 



232 DYNAMOS. 

Let V= the E.M.F. at machine terminals where 

E = total E.M.F. generated. Then, in alternators the E.M.F.'s are 
shown in the following diagram, the load of the alternator 
heing non-inductive, and the armature reaction being neglected, 
2n n LI x Ir =: V at machine terminals. 
V=*(2nnLI) 2 -{-(Ir) 2 when L =: coefficient of self-induction, r = re- 
sistance of armature -\- external circuit. 



Fig. 3. 



CURREIT. 
Continuous Current yi achines. 

The current in a dynamo depends upon 

a. Its E.M.F. 

b. The resistance of its internal circuit -f- the resistance of the external 

circuit on which it is working. 

c. Any counter or opposing E.M.F. in circuit, such as storage batteries 

being charged or motors being run. 
Then let 

E = total E.M.F. of the dynamo, 
e = counter E.M.F. of the circuit, 
R — internal resistance of the dynamo, 
r — resistance of external circuit, 
I— current in amperes flowing. 

Then if the external circuit have no counter E.M.F., as when supplying cur- 
rent for incandescent lamps, 

E 

I = ff , = amperes 

or, if a storage battery is being charged and its opposing E.M.F. = e 

E — e 



then i"= 



R + r 



If E y = external E.M.F. of dynamo as measured by voltmeter at brushes 
at the load in question 

then 1=^ 

T 

Alternating* Current Dynamos. 

In alternating-current machines another factor in addition to the resist- 
ance of the circuits, internal and external, tends to retard or reduce the 
current, viz., the reactance of the circuits (see index for reactance and 
impedance). 

Let L = coefficient of self-induction of armature, 

L' = coefficient of self-induction of external circuit, 
n ■=. number of cycles, ~ 
u) = 2tt n, 
E = open-circuit voltage of alternator, 

other symbols same as for d.c. machine, 
then, reactance = o> L ohms, 



and impedance = Vi? 2 -f-(u) L ) 2 ohms, 

In A.C. dynamos E = Vmean 2 



CURRENTS. 



233 



E, = l{i* + »!/>)' 



11 + r* + taU + v>I? 



(r 2 -f o.I«) 



The inductance L of a circuit in henrys is the ratio — =-; = L 

I (c.g.s.) max. 

xnx ie-« 



&r if i is expressed in virtual amperes then L = 

n $ = Z, / V2 10 8 and the E.M.F. of self-inductance is 

E = V2 n n $ u 10~ 8 where v =r cycles per second, 
or E = 2n v L I volts. 

If u> =. 2irv, oiL = reactance of the circuit in ohms, and the E.M.F. of self- 
inductance of the circuit is = 
M= ItoL ■=. reactance voltage. 



Energy in Balanced Three-phase Circuit. 

In the following diagram of a Y connected multiphase generator and cir- 
cuits, let 

e,= E.M.F. of any phase in the armature, 
i y = current of any phase in the armature, 
E = E.M.F. between mains, 
/== current in any main, 




Fig. 4. 

Wj r=L energy of one phase of the armature, 
W= total energy, 
w, r= e y i, 
but E = e, V§ 
I—i, 

W = 3w, = Z J?LL— 1.732 e L 
V3 

1.732 E 



In the following diagram of a delta connected multiphase generator and 
circuits, let 

e 2 = E 
I=i 2 V3 

w 2 = e 2 i 2 

W=3w ii = ^4/= 1.732 E I 
V3 

1.732 E 




Fig. 5. 



Therefore for any balanced three-phase system, 
the energy is equal to the product of the E.M.F. 
between any pair of mains and the current in one 
main, divided by V3 ; the result being multiplied by the cosine of the angh 
of lag ; i.e., the power factor. 



234 



DYNAMOS. 



If 

then, 



Ii zr resistance per leg of Y-connected armature, 
r = resistance per phase of A connected armature, 



1 2 R loss in Y-connected armature — 3 I 2 R 

I- 1 ' 



I 2 R loss in A connected armature : 



W§, 



r= I 2 r. 



Energ-j in Tbree*pha«e Circuits. 

I, = current in any one of the three wires of external circuit, 
i =z current in one phase of the armature for delta connection, 
W — watts output of a balanced three-phase generator, 
1.732 =V 3 
.577 = 1 -f V3 
E = volts between terminals (or lines) on either delta or Y system, 
v = volts of one phase of the armature if connected in " Y," 
R = resistance per leg, of Y connected armature, 
r =. resistance per phase of A connected armature, 

W— 3 I . v = — '- — = I' E 1.732 (either with Y or A armature. 
V3 
For A 



W 

for A 



3 v, i =z 3 v. 



V3 



— E 



D Jjl J 

W= — ~ = 1.732 E I, which shows statement in brackets to be true. 



V3 



I t - 



W 



E X 1.732 
I, = 1.732 i in delta system. 

I 2 R loss in Y connected armature = 3 I/R. 

I 2 R loss in A connected armature rr 3 ( -~ J r =r I/r. 




E, 




E, 



Fig. 6. 



E=E, 
E = ^E / = 1.732 E r 

I .AMPERES =1.732 x ZOr& 




I AMPERES = 1. 732X Z or y 



/AMPERES = 1.732X2/ or X 



E= E 1 



Fig. 7. 



/ AMPERES = Z 




/ AMPERES = V 



I AMPERES = a? 



Delta Connection. Star or Y Connection. 

FIGS. 8 and 9. Values of current in three-phase connections, where x — y — z. 



CURRENTS. 



235 



Direction of Current in a Conductor. 

To determine in which direction the current in a conductor is flowing, 
place a compass underneath it. If the north pole of the needle points to the 
left, the current is flowing forward or away from the observer. With the 
compass above the conductor, if the north pole of the needle points to 
the right the current is still flowing away from the observer. 

These results are often shown as in the accompanying cuts. 





Fig. 10. 



Fig. 11. 



Direction of Current about an Electromagnet, and 
location of it* Poles. 

If the direction of the current flowing in the wire of the coil is not known, 
then with a magnet find the north pole of the magnet, by approaching the 
compass to one of the poles ; the north-pointing pole will be repelled by the 
north pole of the magnet, but attracted by the south pole. 

Then by placing the right hand on the coil, with the thumb extended at 
right angles and pointing in the same direction as the north pole of the core, 
current will be flowing in the direction pointed by the fingers. 

Of course, if we know the direction of the current, and wish to find the 
north pole of the magnet, placing the hand on top of the coil, as above, with 
the fingers extended in the direction in which the current is flowing, the 
north pole of the core is in the direction in which the thumb is extended. 
Another way is to look at pole of magnet. If current is going round right- 
handed you have a south pole ; if left-handed, a north. See " Corkscrew " 
Rule. 



FIELD MAGNET 



0fl *CT (ON 




"FIELD MAGNET 
NORTH POfcE. 

DYNAMO 



RIGHT HAND. 
Fig. 12. 



Direction of Current in a Dynamo 

Armature. 

A simple rule is : facing the commutator 
of the dynamo, speaking now especially of 
the bipolar type, and assuming the left pole 
to be north or -+-, and the armature to 
be revolving counter clock-wise, then the 
current is flowing to the right across the face 
of the armature, or the left brush is positive, 
or the terminal from which current will 
flow, returning by the negative or right-hand 
brush. 

Reversing the direction of rotation will 
reverse the polarity of the terminals. 

The accompanying figure illustrates a 
graphic method, called Fleming's Right- 
hand Rule. 



236 




DYNAMOS. 



Direction of Rotation in a Motor. 

Knowing the direction of current in the circuit, or which is the posi- 
tive and which the negative terminals of the circuit, the direction of rota- 
tion of the armature can easiest be determined 
by use of the accompanying diagram (Fig. 13), 
which is called Fleming's " left-hand rule." 

field JUag'nets. 

In the paragraph on the E.M.F. of dynamos, 
preceding, the symbol * is used to indicate the 
total flux or quantity of magnetic lines forced 
through the core of the armature by the field 
magnets. 

This value of course depends upon the degree 
of excitation, i.e., the amount of current and 
number of turns of wire on the field magnets. 

To determine this value in an existing ma- 
chine, run it at a proper speed, and measure 
the E.M.F. with a voltmeter. 

riELO MAGNET 

JLnen north pole. 

E x 108 MOTOR LEFT HANQ.-^ 

$ = for continuous current machines, _, 

rev. x n Fig. 13. 

and 

E X 10 8 

$— 7 for alternating current dynamos. 

rev.xn xp Xk 

and if (B = magnetic induction, or Gauss = lines of force per square centi- 
meter, 
and A = area of cross-section of armature core in square centimeters. 

Then density of lines in armature =. (B r= — . 

Magnetic Circuit of a Dynamo. 

The path over which lines of force flow, be it iron or air, is called the 
magnetic circuit, and is subject to laws analogous to those for electric con- 
ductors. It has its magnetic resistance, which is directly proportional to 
the length of the circuit, and inversely proportional to its cross-section and 
permeability, the latter being somewhat analogous to conductivity in an 
electric conductor. 

In a dynamo the path through field-magnet cores, pole-pieces, field-yoke, 
air-gaps, and armature core, forms the magnetic circuit of that machine. 
The calculation of its value follows well-known laws, and is as easily car- 
ried out as the calculation of the resistance or conductance value of an 
electric conductor or path. 

In any piece of iron 
Let I = length of the piece. 

s = cross-section of the same, 

ju. =: permeability = (B -j- JC, 
then the 

magnetic resistance = — called re luctance. 

S /J. 

In the magnetic circuit of a dynamo 
let 

Aa = area of cross-section of armature core, 

A g = area of cross-section of air-gap under the full pole-piece -f a per- 
centage for fringe. 
Am = area of cross-section of magnet core, 
A P = area of cross section of pole-piece, 
A y — area of cross-section of yoke, 
I ±= length of any part, 
•l> = total flux, 



CURRENTS. 



237 



then 

Total reluctance = (-£-) + (-^L.) + (JUL.) + (J*-) + (J?-.) 



call this total reluctance 7?« 
Then 

, 1.257 X w X / 



Jim 



: total flux through magnetic circuit, 



4tt 



where 1.257= — , and b = number of turns of wire, and /recurrent in 
amperes. 



Application of IVIag-netic Circuit to Dynamo Design. 

Let (B = flux per square centimeter, then in any part of t/ie magnetic cir- 
cuit of a dynamo, 

(ft = — , and after it is decided at what induction it is best to work the 
A 

iron of the circuit the cross-section 

& 

The armature core is invariably of laminated soft annealed wrought iron 
or steel, while the magnet cores and yokes are often of cast iron, although 
most generally to-day some part, if not all, of the core is of mild cast steel. 
If cast iron is used, it is only necessary to increase the cross-section to 
satisfy the equation 

A=* 

(B 

Experience has shown that there is a very considerable leakage of lines of 
force in an electro magnet ; some cutting across without going through the 
armature path, others leaking across corners, etc. This leakage, amounting 
to 30 to 50 per cent of the the total flux, has to be made up by increasing the 
ampere turns of the magnets beyond that necessary to furnish the requisite 
flux for the armature part of the circuit, by a percentage or amount repre- 
sented by the leakage. 

This le'akage has been determined for different types of field magnets by 
Edison and others, and a table of such values follows. In dynamo calcula- 
tion the leakage value may be represented by v. 

Stray Field in Dynamos. 



Name of Dynamo. 


Field. 


Arma- 
ture. 


Remarks. 


Value 
of v. 


Edison-Hopkinson 


Bipolar 


Drum 


Poles next to bed-plate 


1.32 


Edison (American) 


Bipolar 


Drum 


Poles next to bed-plate 


1.40 


General Electric Co. 


Multipolar 


Drum 


Direct driven 


1.25 


Kapp 


Bipolar 


Drum 


Yoke next to bed-plate 


1.30 


Siemens .... 


Bipolar 


Drum 


Yoke next to bed-plate 


1.30 


Manchester . . . 


Double magnet 


Long 


Bed and one pole cast 


1.49 




2 pole 


ring 


together 




Ferranti .... 


Double magnet 


core- 


Ordinary pattern alter- 


2.00 




Multipolar 


lessdisk 


nating. 





The following formulae are useful in calculating approximately the mag- 
netic leakage in a dynamo : 



238 



DYNAMOS. 



1. The permeance, or reciprocal of magnetic reluctance, between two 
parallel opposed surfaces is 

2d 

where d is the distance between the surfaces in centimeters, and where A v 
and A 2 are the areas of the surfaces in square centimeters (see Fig. 14). 



-d-tta 



Mm 



Fig. 14. 



Fig. 15. 



2. The permeance between two equal rectangular areas situated in the 
same plane, having corresponding sides parallel and a common axis of sym- 
metry, is 

L, ID\ .„ D . 



Iff. 



if -J- is large (see Fig. 15), 



1 + 



Tv(D-d) 



if -=- is not large (see Fig. 16), 




where L = length of each rectangle, measured perpendicularly to common 
axis of symmetry (i.e., to the plane of the paper in the figure) 
in centimeters. 
d = distance between adjacent parallel sides in centimeters. 
D — distance between remote parallel sides in centimeters. 
3. The permeance between two equal rectangular areas at right angles to 
one another, having one pair of sides in the one parallel to the correspond- 
ing pair in the other, is 



2L, 



lije 



2D-{-d(n 



2) 



where d, Z>, Z ]( and i 2 are the lengths in centimeters 
of the dimensions shown in Fig. 17. 
If d = Jj, the permeance in this case becomes 



vM'-si) 






As the resistance of the two air-gaps in any dynamo Fig. 17. 

is usually more than 80% of the total resistance of the 

magnetic circuit, the length of the iron part of the circuit is of little conse- 
quence excepting in cost of material, and is determined largely by the 
amount and style of winding necessary for the field magnet coils. 

Other considerations govern the length of air-gap, such as sparking at 
the brushes, heating of pole-tips, heating of teeth in Paccinotti ring, regula- 
tion of voltage, current, etc., thus compelling the use of more magnetizing 
force to overcome that part of the circuit than all other parts combined. 
If 



then 



Em = total reluctance of the magnetic circuit of a dynamo, 



ampere turns = 



» Rm 
1.257 



CURRENTS. 239 

and,, as it is necessary to know the ampere-turns required for each part of 
the circuit, the items may be tabulated as follows : — 

Formulae for Different partis of the JlEag-netic Circuit of a 

Dynamo. 
Square centimetre units. 

Armature core ; ampere-turns = <£ X — ; 1.257 

AaX Ha ' 

The two air-gaps ; ampere-turns = $ X —?- — 1.257 

Ag 
7„ 

Magnet cores ; ampere-turns =: <3> X 

Pole-pieces ; ampere-turns = $ X 

Yoke ; ampere-turns = $ X . 

Ay X V-y 



Am X M™ 


-^ 1.257 


h 


4- 1.257 


A P X HP 


h 


— 1.257 



For square inch units the divisor will be 1.257 x 2.54 = 3.193, or better, 
multiply by — ^ = .3132. The formulae are then, for square inch units, 

Armature core ; ampere-turns = $ X —. — X .3132 

Aa X M« 

The two air-gaps ; ampere-turns = $ X -f X .3132 

Ag 

Magnet cores ; ampere-turns = $ X —r— X .3132 

Am X |H» 

Pole-pieces ; ampere-turns = $ X -: — - — X .3132 

Ap X HP 

Yoke ; ampere-turns = $ x —. — X .3132 

Ay X Hy 

Types of Dynamos as Determined hy their Connections. 

There are five types of dynamo connections in common use in the United 
States, viz.: — 

1. Magneto machines. 

2. Separately excited machines. 

3. Series machines. 

4. Shunt machines. 

5. Compound wound machines ; this last having two classes, i.e., long 
shunt and short shunt. 

The above types apply especially to continuous current dynamos, but alter- 
nating current machines are usually made separately excited as per No. 2, 
and are sometimes made self -excited , from separate coils on the armature, 
connected to a commutator on the shaft adjacent to the collecting-rings. 

Other alternating current dynamos, in fact nearly all those used in the 
United States to-day for lighting, or for lighting and power purposes, that 
have been constructed since 1891, are of the type known as composite wound, 
in which the fields are separately excited from an outside source, and in 
addition to this a heavy wire series winding is also wound on the field coils, 
and a portion of the current from tbe main circuit is shunted through them, 
being passed through a commutator on the armature shaft first to be 
rectified. 

This current is of course in proportion to that flowing in the main circuit, 
and adds excitation in proportion to the load, thus keeping the terminal 
pressure practically constant under all conditions. Alternators for trans- 
mission of power are not " composite " wound. 



240 



DYNAMOS. 



Compensated Revolving* field Alternators. 

The General Electric Company in October, 1899, placed on the market a 
new type of multiphase alternator, which is claimed to overcome many of 
the faults common to the old style of machine, especially when used on 
combined lighting and motor loads. While it has been found a compara- 
tively easy matter to compound and over-compound for non-inductive loads, 
it has been heretofore quite difficult to add excitation enough to compound 
for inductive loads which require considerably more field current than do 
loads of a non-inductive nature. 

The following description is taken from the bulletin issued by the makers 
describing the machine, which is of the revolving field type : — 

" The means by which this result is accomplished are as follows : The 
shaft of the alternator which carries the revolving field carries also the 
armature of the exciter, which has the same number of poles as the alter- 
nator, so that the two operate in synchronous relation. In addition to the 
commutator, which delivers current to the fields of ooth the exciter and the 
alternator, the exciter has three collector rings through which it receives 
current from one or several series transformers inserted in the lines leading 
from the alternator. This alternating current, passing through the exciter 
armature, reacts magnetically upon the exciter field in proportion to the. 
strength and phase relation of the alternating current. Consequently the 
magnetic field and hence the voltage of the exciter, are due to the combined 
effect of the shunt field current and the magnetic reaction of the alternating 
current. This alternating current passes through the exciter armature in 
such a manner as fro give the necessary rise of exciter voltage as the non- 
inductive load increases, and without other adjustment, to give a greater 
rise of exciter voltage with additions of inductive load." 

Following are cuts of the types mentioned above. 




Fig. 20. 



magneto dynamo 
Fig. 18. 



separately excited dynamo 
Fig. 19. 





SHUNT WOUND 
DYNAMO 

Fig. 21. 



COMPOUND WOUND 
DYNAMO SHORT SHUNT 

Fig. 22. 





/ 




\ 




















^< 




b 




J 















COMPOUND WOUND 
DYNAMO LONG SHUNT 



Fig. 23. 



CURRENTS. 



241 



CONNECTIONS OF TYPE AS SINGLE-PHASE 

ALTERNATING CURRENT GENERATORS 

WITH COMPOSITE FIELD 2300 VOLTS 

jflS 6-50-900 Form rt 
&S 0-90-900 Form 7=1 
JSS ©-120-S00 




Col lector. side 



Commutator-Col lector J 

Manner of Placing Spools. 

The observer is supposed to be looking at 
faces of pole pieces marked A and B. The 
series field winding should be nearest the 
armature — that is, toward the observer. 
The arrows correspond to those on spool 
flanges, the spools being so placed that the 
arrows point in opposite directions on each 
succeeding spool. 

Fig. 24. — General Electric Composite wound alternator. 



242 



DYNAMOS 



CONNECTIONS OF TYPE AS SINGLE-PHAS£ 

ALTERNATING CURRENT GENERATORS 

WITH COMPOSITE FIELD 1150 VOLTS 



#S> 6-60-900 For 

jqs e-90-900 r< 
jqs a-120-900 



BE 



Collector s'de 




Commutator-Collector 



Manner of Placing Spools. 

The observer is supposed to be looking at 
faces of pole pieces marked A and B. The 
series field winding should be nearest the 
armature — that is, toward the observer. 
The arrows correspond to those on spool 
flanges, the spools being so placed that the 
arrows point in opposite directions on each 
succeeding spool. 

Fig. 25. — General Electric Composite wound alternator. 



CURRENTS. 



248 



CONNECTIONS OF TYPE AS SINGLE-PHASE 
ALTERNATING CURRENT GENERATORS 
WITH COMPOSITE FIELD S300 VOLTS 

A<r> IO-30-1 50O Form A ^, -^ AS 14-120-1070 Form 

A5 10-60 -1 500 Form/ 




«CoJ lector side . !_, 



Commutator-Col lector- 



Manner of Placing Spools. 

The observer is supposed to be looking at 
face of pole piece marked A. The series 
field winding should be nearest armature, 
that is, toward observer. The arrows cor- 
respond to those on spool flanges, the spools 
being so placed that the arrows point in 
opposite directions on each succeeding spool. 

Fig. 26. — General Electric Composite wound alternator. 



244 



DYNAMOS. 



CONNECTIONS OF TYPE! AS SINGLE-PHASE 

ALTERNATING CURRENT GENERATORS 

WITH COMPOSITE FIELD 1150 VOLTS 



AS 10-30-1500 Form A 
AS 10-60-1500 Form A 



AS 14-120-1070 Form A 




Commutator-Col lector 



Manner of Placing Spools. 

The observer is supposed to be looking at 
face of pole piece marked A. The series 
field winding should be nearest armature, 
that is, toward observer. The arrows cor- 
respond to those on spool flanges, the spools 
being so placed that the arrows point in 
opposite directions on each succeeding spool. 

Fig. 27. — General Electric Composite wound alternator. 



CURRENTS. 



245 



Magneto dynamos are now used in the United States only for ringing tele- 
phone bells, and for other signalling purposes. 

Separately excited dynamos are seldom used, except for alternating current 
production ; with the exception that one occasionally finds a straet railway 
power-house where the shunt fields of all the dynamos are separately excited 
from one generator. 

Series dynamos are used for arc lighting on constant current circuits, 
where many lamps are distributed over wide area The constant potential 
arc lamp, both for continuous and alternating currents, has reached such a 
degree of perfection and low cost as to encourage its use to a very great 
extent to displace the old style constant current lamp. Series dynamos are 
also often used as boosters to vary the voltage on a line automatically in 
proportion with load. 

Shunt dynamos are used for charging storage batteries, and for large cen- 
tral stations supplying constant potential current, and this applies especially 
to the " Edison " stations throughout the country. It is easier to adjust the 
load between large machines when shunt wound, and in these large stations 
attendance is always at hand. 

Compound wound dynamos are used in street railway power-houses, in 
order to keep the pressure somewhere near constant under the great varia- 
tion in output ; and are used to a very considerable extent, it may be said 
almost wholly, in isolated plant work, in order to save attendance and 
adjustment of the field rheostat. 

D1IKAMO CHARACTERISTICS. 

Dr. John Hopkisson is said to have devised the " characteristic " or curve 
of properties of the dynamo, to show the results to be expected in a certain 
design of machine, and to indicate actual results after completion, although 
it is also said that Deprez first used the name. 

The characteristics most commonly developed are as follows : — 

1. Magnetization or saturation curve. 

2. External characteristic. 

3. Curve of magnetic distribution. 

1. magnetization Curve. — This curve is always determined for 
each newT;ype of dynamo by reputable builders, and can easily be determined 
by any one having available a separate exciting current, a voltmeter, and 
an ammeter. 

The turns of wire on the field remaining the same, it is sufficient to read 
the amperes in the field, voltage at the brushes, and revolutions of the arm- 
ature. Curve, Fig. 28, following shows the result of such a test. In a case 
where, like the above, the dynamo is already in existence, the field is ex- 
cited from some outside source, and the 
curve determined by gradual increase 
of the current in the field, and the volts 
at the brushes are read after each such 
change. 

The accompanying curve is the re- 
sultant of the magnetizing force neces- 
sary to force the flux through the 
following parts, in the case of a bipolar 
dynamo, all of which may be of differ 
ent character : — 

a. Armature core. 

b. Two air-gaps. 

c. Two polec-pieces. 

d. Yoke. 

e. And to overcome leakage of mag- 




AMPERE -TURNS ON FIELD 
OR CURRENT IN FIELDS 



Fig. 28. Magnetization Curve. 



netic lines. 

Individual curves for each of these parts can be predetermined by use of 
formulas for calculating the magnetic circuit of dynamos, and from a com- 
bination of those curves the curve shown above can be constructed, showing 
the aggregate excitation necessary to produce certain voltages. 

For sample of such a composite curve the reader is referred to page 149 
of the fifth edition of S. P. Thompson's book, Dynamo Electric Machinery. 

This curve is valuable not only to show the character of one machine, but 
is useful to compare different machines by, and for that reason some stan- 



24:6 



DYNAMOS. 



dard ratio of the scales on which the curves are based should be settled 
upon. 

2. external Characteristic. — This curve is a curve of results, in 
which the dynamo is excited from its own current, and with the speed con- 
stant, the terminal voltage is read for different values of load. 

The curves for series, shunt, aud compound wound machines all differ. 

The observations are best plotted in a curve in which the ordinates repre- 
sent volt values, and abscissas amperes of load. 

Series dynamo. In a series machine all the current flowing magnetizes 
the field, the volts increase with the current, and if fully developed the 
curve is somewhat like the magnetization curve, being ahvays below it, 
however, due to the loss of pressure in overcoming internal resistance and 
armature reactions. 

The following diagram (armature reaction being neglected) is a sample of 
the external characteristic of a series dynamo. 

To construct this curve from an existing 
machine, the curve of terminal voltage can 
be taken from the machine itself by driving 
its armature at a constant speed, and varying 
the load in amperes. 

The curve " drop due to internal resistance," 
sometimes called the " loss line," can be con- 
structed by learning the internal resistance 
of the machine, and computing one or more 
values by ohms law, and drawing the straight 
( line through these points, as shown.' 

The curve of total voltage is then con- 
structed by adding together the ordinates of 
the " terminal voltage " and " drop due to 
internal resistance." 

A very good sample of curve from a modern 
series machine is to be found in the following 
description of the Brush arc dynamo. 

Following is a characteristic curve of the new Brush 125-lt. Arc Dynamo 



VO LTAGE 




AMPERES LOAD 



Fig. 29. External Charac- 
teristic of Series Dynamo. 



5000 
4500 

4000 
^3500 

>3000 
2500 
2000 
1500 

















_— 




















-J. 


/" 












\ 
















/ 














\ 
















t 
















\ 












/ 


















































































































































































i 






























/ 






























/ 




























































/ 




























/ 






























/ 






CHARACTERISTIC CURVE 
SPEED-500 REV. PER MIM. 










/ 














/ 




























































f 





























io ii 12 ia u 



Fig. 30. Characteristic curve of Brush 125-Light Arc 
Dynamo without Regulator. 



DYNAMO CHARACTERISTICS. 



247 



machine without any regulator. The readings were all taken at the spark- 
less position of commutation. This curve is remarkable from the fact that 
after Ave get over the bend, the curve is almost perpendicular, and is prob- 
ably the nearest approach to a constant current machine ever attained. 
By winding more wire on the armature the machine could have been made 
to deliver a constant current of 9.6 amperes at all loads, without shunting 































































































































so 










































80 
















































/ 


































TO 






/ 








































/ 




































60 




/ 










ELECTRICAL EFFICIENCY 

AMPERES 9.S 

SPEED BOO R.P.M. 














' 




















50 
































































.40 

















































































Fig. 31. Electrical Efficiency Curve of 
Brush 125-Light Arc Dynamo. 

































1 






























































































































































































































































/ 


y 






































< 






































/ 










COMMERCIAL 


:fficiency 

3 9.6 












/ 












AMPERE 












/ 












SPEED BOO R.P.M. 



































































































































Fig. 32. Commercial Efficiency Curve of 
Brush 125-Light Arc Dynamo. 



any of the current from the field ; but this would have increased the internal 
resistance, and also have made the machine much less efficient at ligbt 
loads. By the present method of regulation the J' 2 E loss at one-quarter load 
is reduced from 4,018 to 3,367 watts, the gain being almost one electrical 
horse-power. 

Fig. 31 is a curve of the electrical efficiency. It will be noticed that this 
at full load reaches 94 per cent, which is accounted for by the liberal allow- 
ance of iron in the armature, thus reducing the reluctance of the magnetic 
circuit, and by the large size of the wire used on both field and armature. 

Fig. 32 is a curve of the commercial efficiency. At full load this is 3ver 
90 per cent, and approaches very closely the efficiency of incandescent 
dynamos of equal capacity, but the most noteworthy point is the high effi- 
ciency shown at one-quarter load. 

Fig. 33 is a curve of the machine separately excited, with no current in the 
armature. The ordinates are the volts at the armature terminals, and the 
abscissa) the amperes in the field. This is in reality a permeability curve of 
the magnetic circuit. By a comparison of the voltage shown here when 



248 



DYNAMOS. 



there are nine amperes in the field, with that of the machine when deliver- 
ing current, can he seen the enormous armature reaction. The curve also 

































9000 






























































8000 


































































































































/ 
































/ 




























5 5000 




/ 






























/ 


























































































































































2000 


















E. M. F. 








































































1000 
500 































































2, 3 4 5 6 



10 11 12 13 14 15 



Fig. 33. Permeability Curve of Magnetic Circuit 
of Brush 125-Light Arc Dynamo. 

indicates a new departure in arc dynamo design, namely, that the magnetic 
circuit is not worked at nearly as high a point of saturation as in the old 
types. 

Shunt dynamo. The shunt dynamo has, besides an external characteristic, 
shown below, an internal characteristic. The first is developed from the 
volts read while the load in amperes is being added, the armature revolu- 
tions being kept constant. 

Adding load to a shunt dynamo means simply reducing the resistance of 
the external circuit. With all shunt machines there is a point of external 
resistance, as at n, beyond which, if the resistance is further reduced, the 
volts will drop away abruptly, and finally reach zero at a short circuit. 




Fig. 34. External Characteristic 
of Shunt-wound Dynamo. 



Fig. 35. Internal Character- 
istic of Shunt Dynamo. 



The internal characteristic, or, more correctly, curve of magnetization, of 
a shunt dynamo, is plotted on the same scale as those previously described, 
from the volts at the field terminals and the amperes flowing in the field. 



DYNAMO CHARACTERISTICS. 



249 



The resistance line o a only applies to the point a on the curve, and the 
resistance value a b for that point is determined hy ohms law, or as fol- 
lows : As the curve of magnetization is determined from the reading of 

volts plotted vertically and amperes horizontally, and as r = -y or r = 

1 o b 

and — -r = tang a ob, therefore the resistance at any point on the curve will 

be the tangent of the angle made by joining that point to the origin o. 

Compound dynamo. As the compound dynamo is a combination of the 
series and shunt machines, the characteristics of both may be obtained 

from it. 

The external characteristic is of con- 
siderable importance where more than 
one dynamo is to be connected to the 
same circuit, or when close regulation 
is necessary. 

Fig. 36 is a sample curve from a com- 
pound-wound dynamo, where the in- 
crease of magnetization of the fields 
due to the series coils and load causes 
the terminal voltage to rise as the load 
is increased. This is commonly done 
to make up for drop in feeders to the 
centre of distribution. It is impossi- 
ble in ordinary commercial dynamos 



Fig. 36. Characteristic of Over- 
compounded Compound - wound 
Dynamo. 

to make this curve closely approach a straight line, and the author has 
found it difficult for good makes to approach a straight line of regulation 
nearer than 1J per cent either side of it for the extreme variation. 

Curve of Jfiag-netic Distribution. — This curve is constructed 
from existing dynamos to show the distribution of the field about the pole- 
pieces ; it can be plotted on the regular rectangular co-ordinate plan, or on 
the polar co-ordinate. 

The following cuts illustrate the commonest methods of getting the data 
for the curve. With the dynamo running at the speed and load desired, the 





Fig. 37. 



Fig. 38. 



pilot brush, a, in the first cut, or the two brushes, a and b, in the second cut, 
is started at the brush x, and moving a distance of one segment at a time, 
the difference in volts between the brush x and the location of the pilot 
brush, a, is read on the voltmeter. 

Where the one pilot brush is used, the total difference between that and 
the origin is read ; while with two brushes, as a and b, which are commonly 
fastened to a handle in such a manner as to be the width of a segment apart, 
just the difference between the two adjacent segments is read, and the total 
difference is determined by adding the individual differences together. 



250 DYNAMOS. 



In taking the distribution curve on a commutator, -with the two-brush 
method of S. P. Thompson, the curve of potential may be plotted in two 
ways, viz. : the heights of the ordinates may be made equal to the sum of 
all the readings to the given point, or they may be made equal to the reading 
at each bar, in which case the curve will indicate the value of the induction 
at each point of the held where a reading is made. 

Potential curves of this kind are often plotted on a circle, the circle itself 
representing the commutator, with the segments plotted as radial ordi- 
nates, which are made equal in value to the readings of the voltmeter 
brushes. 

AMMATTUMES. 

Armatures for continuous current dynamos differ much in practice from 
those xised for alternating-current machines, although the former produce 
alternating currents that are rectified or turned in the same direction by a 
commutator. 

Direct-current armatures are divided into two general forms, — drum arma- 
tures, in which the conductors are placed wholly on the surface or ends of 
a cylindrical core of iron ; and ring armatures, in which the conductors are 
wound on an iron core of ring form, the conductors being wound on the out- 
side of the ring and threaded through its interior. 

Another form used somewhat abroad is the disk armature, in which the 
conductors are arranged in disk form, the plane of which is perpendicular to 
the shaft, and without iron core, as the disk revolves in a narrow slot be- 
tween the pole-pieces. 

"Armature Cores. 

In some early dynamos cores were made of solid iron ; but the heat from 
Foucault or eddy currents was found so excessive as to endanger the insula- 
tion of the conductors, and the loss in the core reduced the efficiency greatly. 
Iron wire wound on a frame constructed for the purpose was then intro- 
duced in place of solid cores. This answers the purpose for ring armatures 
fairly well, but there is considerable waste space, as round wire is always 
used. 

To-day armature cores are invariably made of thin sheet iron or annealed 
soft steel from .015 to .025 inch thick. 

In order to prevent Foucault currents in such laminated cores, it is necessary 
to insulate the disks from each other in some manner. Very thin tissue 
paper between disks, rust on the surfaces, varnish, oil, or paint, are all 
used for the purpose. Most of the better builders of to-day use a light 
japan on the disks, with a layer of good insulating paper about every half 
inch. Open spaces are left in the core about every two inches for ventila- 
tion. 

Armature cores are divided a,gain as to outer surface into smooth body 
and toothed; the latter called form erly the Pacinnotti armature, after its 
inventor. 

The smooth body armature core is enough smaller in diameter than the 
inner circle of the pole faces, to allow laying on the winding ; the full 
diameter of the toothed armature core is only enough smaller than the field 
pole space to allow proper air-gap, and slots are provided in its periphery in 
Avhich are laid the conductors. The toothed, ring armature is used to-day in 
the United States to perhaps a greater extent than any other form, although 
the winding is of the drum form used with multipolar dynamos. 

The toothed armature is said by Professor Crocker to possess the follow- 
ing advantages and disadvantages over the smooth body. 

Advantages : 

1. The reluctance of air-gap is minimum. 

2. The conductors are protected from injury. 

3. The conductors cannot slip along the core by action of the electrody- 
namic force. 

4. Eddy currents in the conductors are avoided. 

5. If the teeth are practically saturated by the field magnetism, they 
oppose the shifting of the lines by armature reaction. 



ARMATURES. 251 



Disadvantages . 

1. More expensive. 

2. The teeth tend to generate eddy currents in the pole-pieces. 

3. Self-induction of trie armature is increased. 

If the slots are made less in width than 1\ or 3 times the air-gap, so that 
the lines spread and become nearly uniform over the pole faces, but little 
effect will be felt from eddy currents induced in the pole faces. When it is 
not possible to make such narrow slots, pole-pieces" must be laminated in 
the same plane as the disks of the armature core, or the gap must be consid- 
erably increased. 

Hysteresis in the armature core can be avoided to a great extent by using 
the best soft sheet iron or mild steel, which must be annealed to the softest 
point by heating to a red heat and cooling very slowly. Disks are always 
punched, and are somewhat hardened in the process ; annealing will not 
only remove the hardness, but will remove any burrs that may have been 
raised. 

Disks should be punched of such careful dimensions as to need no filing or 
truing jp after being assembled. Turning* down the surface of a smooth- 
body armature core bui-rs the disks together, and is apt to cause dangerous 
heating in the core when finished. Light filing is all that is permissible for 
truing up such a surface. Slotted cores should be filed as little as possible, 
and can sometimes be driven true with a suitable mandril. 

End plates of iron are seldom satisfactory, and the use of gun metal or 
other bronze is to be commended. Bolts through the core must be insulated, 
or currents will be induced in them as in any conductor. 

Cores were formerly designed of small diameter, especially so in those of 
the drum type ; but now the dimensions of the core take no particular shape, 
excepting in some cases it is said to be better to make the cross-section of 
each side of ring-armature cores approximately square, although cores of 
a rectangular cross-section answer better the purpose for avoiding excessive 
heating, and for least cost. 

The size of core is determined first by the number and size of conductors 
it has to carry to produce the required E.M.F. ; and secondly, by the surface 
necessary to avoid excessive rise of temperature. 

Armature conductors are usually made 600 to 800 circular mils per ampere, 
and the number of paths through the armature between which the current 
is divided is determined by the design of the winding and the number of 
poles. In a bipolar closed-coil winding there are two paths, each carrying 
one-half the total current, while a four-pole closed-coil winding may have 
either two or four circuits. The method of determining the number of con- 
ductors necessary to produce the required E.M.F. is explained in the early 
part of this chapter. For losses in cores of armatures, see chapter on Mag- 
netic Qualities of Iron. 

Armature shafts must be very strong and stiff, to avoid trouble from the 
magnetic pull should the core be out of centre. They are made of machin- 
ery steel, and have shoulders to prevent too much side play. 

Core Insulation. — A great variety of material is used for insulating 
the core, including asbestos, which is usually put next to the core to prevent 
damage from heating of that part ; oiled or varnished paper, linen, and silk ; 
press board ; mica and micanite. For the slots of slotted cores the insula- 
tion is frequently made into tubes that will slide into the slots, and the con- 
ductors are then threaded through. Special care must be taken at corners 
and at turns, for the insulation is often cut at such points. The armature 
conductors of the Niagara dynamos are insulated by a layer of mica wound 
on to the bar § inch thick, and then pressed, into place under high and hot 
steam pressure. 

Armature Windings. 

For all small dynamos, and in many of considerable size, the winding is of 
double cotton-covered wire. Where the carrying capacity is more than the 
safe carrying capacity of a No. 8 B. & S. gauge, the conductor shordd be 
stranded. In large dynamos, rectangular copper bars, cables of twisted cop- 
per, and in some cases large cable compressed into rectangular shape, are 
more commonly used. If the copper bars are too wide, or wide enough so 
that one edge of the bar enters the field perceptibly before the remaining 



252 



DYNAMOS. 



parts of the bar, eddy currents are induced in it ; such bars are therefore 
made quite narrow, and it is common to slope the pole face a trifle, so that 
the bars may enter the field gradually. 

Methods or arrangement of windings are of a most complex nature, and 
only the most general in use will be described here, and these only in theory. 
Parshall & Hobart have described about all the possible combinations ; 
S. P. Thompson, Hawkins & Wallis, and others have also written quite fully 
on the subject. 

Unipolar io hidings are not windings at all, as the armature is simply a 
cylinder or disk of metal ; and as none have as yet been put to practical use, 
no further comment will be made on them. 



Ring- or Gramme Windings. 



The form of core does not to-day determine the form of winding, for, 
while the drum core is always of necessity wound with the drum winding, 
the ring core can be wound with either the ring or drum winding, as will be 
explained. 

The simplest form of ring winding is the two-circuit single winding, where 
a continuous conductor is wound about the ring, and taps taken off to the 
commutator at regular intervals. 




Fig. 39 



Fig. 41. 

The first variation on this will be the multi-circuit single winding, used 
where there are more than one pair of poles. Fig. 40 shows the four- 
circuit single ivinding. 

Where it is advisable to reduce the number of brushes in use, the multi- 
circuit winding can be cross-connected ; that is, those parts of the winding 
occupying similar positions in the various fields are connected in parallel to 
the same commutator bar. Fig. 41 shows one of the simplest forms of 
cross-connected armatures. 

Where, from the shape of the frame, the magnetic circuits are somewhat 
unequal, the winding shown in Fig. 42 Avill average up the unequal 
induction values, and prevent sparking to some extent. It also halves the 
number of commutator segments ; that is, there are two coils connected 
to each segment instead of one, as in the previously mentioned windings. 
If ?i = number of coils, and p = number of poles, any coil is connected 

across to one - ±1 in advance of it. 

Multiple Windings for Ring- Armatures. — An important class 
of windings much in use at present, and for many purposes invaluable, is 
the double, triple, quadruple, etc., wound ring In these classes two or 
more entirely separate and distinct windings are employed, each connected 
to its own set of segments, the segments of the different windings following 
each other in consecutive order. 

Fig. 43 shows the simplest form of two-circuit double ivinding, used in 



ARMATURES. 



253 



a bipolar machine. As no two segments of the same circuit are adjacent, 
the liability of short-circuit of the commutator is diminished. 

Two-circuit Winding's for multipolar fields. — This is an 
important class of windings, and, as it has but two circuits irrespective of 
the number of poles, has the advantage over the multiple-circuit windings 

2 
that it needs but — as many conductors as are necessary in that class, and 

2 
therefore needs but - as much space for insulation. 

n 
But two sets of brushes are necessary for the two-circuit windings, unless 
the current is heavy enough to require a long commutator, in which case 
other sets of brushes can be added, up to the number of poles. 




Fig. 42. 



In the short-connection type of this class, conductors under adjacent field 
poles are connected together so that the circuits from brush to brush are 
influenced by all the poles, and are therefore equal. 

In the long-connection type the conductors under every other pole are con- 
nected, so that the conductors from brush to brush are influenced by but 
one-half the number of poles. 

The number of coils in a two-circuit long-connection multipolar ivinding is 
determined by the formula 



where S = the number of coils, n = the number of poles, and y ■= the 
pitch. The number of commutator segments is equal to the number of 
coils, and must be odd for machines with an even number of pairs of poles, 
but may be either odd or even for machines having an odd number of pairs 
of poles. 

The pitch, y, is the number of coils advanced over for end connections, as, 
for instance, in an armature with a pitch of 7 the end of coil number 1 is 
connected to the beginning of coil 1 + 7 = 8, and from 8 to 8 + 7 = 15, and 
so on. In multipolar ring long-connection windings y may be any integer, 
but not so in drum windings. 

Mr. Kapp gives, in the following table, the best practice as to angular 
distance between brushes for this class of windings. 



254 



DYNAMOS. 



Number 
of poles. 


Angular distance between brusbes. 




Degrees. 


Degrees. 


Degrees. 


Degrees. 


Degrees. 


2 


180 










4 


90 










6 


60 


180 








8 


45 


135 








10 


36 


108 


180 






12 


30 


90 


150 






14 


25.7 


77 


128 


180 




16 


22.5 


67.5 


112 


158 




18 




60 


100 


140 


180 


20 




54 


90 


126 


162 



Fig. 44 shows a simple form of two-circuit multipolar single winding, and 
Fig. 45 another sample as used with a greater number of poles. 




Fig. 45. 

Both of the above samples are of the long-connection type. In the short- 
connection type the formula for determining the number of coils is 

S=zny ± 2, 
and Fig. 46 is a sample diagram of one of the type. 

Two-circuit IVEultipiv-wouml Multipolar II in cm. — The for- 
mula for determining the number of coils and other factors for this class 
of windings is 



ARMATURES. 



255 



s = ^xy 



m 



where S = number of coils, 

n = number of poles, 
y = pitcb, 
m = number of windings, as double, triple, etc. 

" m " Avill equal a number of independently re-entrant windings equal to tbe 
greatest common factor of y and m. 




Fig. 4G. 

The following figure is a diagram of a two-circuit doubly re-entrant, double 
wound ring armature : 




S 

Fig. 47. 
Fig. 48 is a diagram of a two-circuit, singly re-entrant, double-wound ring. 



Drum Winding's. 

In order that the E.M.F.'s generated in the coils of a drum armature may 
be in the same direction, it is necessary that the two sides of each coil be in 
tields of opposite polarity, and therefore the sides of the coils are connected 



256 



DYNAMOS. 



across the ends of the core ; directly across, for bipolar machines, and part 
way so for those of the multipolar type. 




Fig. 48- 

Figure 49 shows the S^on Hefner- Alteneck drum winding, used principally 
in small and smooth core armatures. 




Fig. 49. 

A sample of two-layer, two-circuit single winding is shown in Fig. 50. 

IlEultiple-circuit Sing-le-wound, multipolar Drums. — In this 
class of winding there must be an even number of bars ; and for single wind- 
ings the pitch at one end must exceed that of the other by 2, and must both 
be odd. If n is the number of poles, and c the number of face conductors, 

the average pitch y should be about — . For chord windings y should be as 



much smaller than — as convenient. 
n 



ARMATURES. 



257 



In iron-clad windings the number of conductors must be a multiple of the 
number of conductors per slot. 




Fig. 50. 
Following is a diagram of a six-circuit, single winding. 
I IM 




Fig. 51 

Two-circuit, Single-wound, Drum Armatures. — In this type 
of winding, the pitch y is always forward, and must be an odd number, the 
connections leading the winding from a certain bar under one pole to a bar 
similarly situated under the next pole in advance. Two-circuit drum wind- 



ings have for a given voltage 
windings. 



as many conductors as multiple-circuit 



258 



DYNAMOS. 



When as many sets of brushes are used as there are poles, careful adjust- 
ment of the brushes is necessary in order to avoid excessive flow of current 
and bad sparking at any one set of brushes, with symbols the same as in the 
previous paragraph, c = n y ± 2. 

The following diagram shows the connections of a two-circuit single 
winding. 




Fig. 52. 



Two-circuit, JIultinle-wouml. I»rum Armatures.— "With the 
same symbols as before, and m = number of windings, the general formula 

is c = n y ± 2 in. 




Fig. 53. 



ARMATURES. 



259 



This is a large class, and many combinations have been worked, Figs. 53 
and 54 showing two of the simpler ones ; the first a two-circuit triple wind- 
ing, and the second a two-circuit double winding. 




Alternating: current Armatures, 



Almost any continuous current armature winding may in a general way 
be used for alternating currents, but they are not well suited for such work, 
and special windings better adapted for the purpose are designed. 

Alternating current armature windings are open-circuit windings, except- 
ing in the rotary converter, where the rings are tapped directly on to the 
direct current armature windings. 

Early forms of armature windings of this type, as first used in the United 
States, had pan-cake or flat coils bound on the periphery of the core. In 
the next type the coils were made in a bunched form, and secured in large 
slots across the face of the core. Both these types were used for single- 
phase machines. After the introduction of the multiphase dynamo, arma- 
ture windings began to be distributed in subdivided coils laid in slots of the 
core ; and this is the preferred method of to-day, especially so in the case of 
revolving field machines. 

The single coil per pole type of winding gives the larger E.M.F., as the 
coils are thus best distributed for influence by the magnetic field. This type 
also produces the highest self-induction with its attendant disadvantages. 

The pan-cake and distributed-coil windings are much freer from self-induc- 
tion, but do not generate as high E.M.F. as does the single-coil windings. 

In well-considered multiphase windings the E.M.F. is but little less for 
distributed coils than for single coils, and has other advantages, especially 
where the use of step-up transformers permits the use of low voltages, and 
consequently light insulation for the coils. The distributed-coil winding 
offers better chance for getting rid of heat from the armature core, and the 
conductor can in such case be made of less cross-section than would be 
required for the single-coil windings. 

The greater number of coils into which a winding is divided, the less will 
be the terminal voltage at wo load. Parshall & Hobart give the following 
ratio for terminal voltage under no-load conditions : 



260 



DYNAMOS. 



Single-coil winding =r 1. for the same total number of conductors, the 
spacing of conductors being uniform over the whole circumference. 
Two-coil winding r= .707. 
Three-coil winding = .667. 
Four-coil winding = .654. 

When the armature is loaded, the current in it reacts to change the termi- 
nal E.M.F., and this may be maintained constant by manipulation of the 
exciting current. With a given number of armature conductors this reac- 
tion is greatest with the single coil per pole winding, and the ratios just 
given are not correct for full-load conditions. 

Single-phase Winding's. — The following diagram shows one of the 
simplest forms of single-phase winding, and is a single coil per pole winding. 




Fig. 55. 

Another similar winding, but Avith bars in place of coils, is shown in the 
following figure. It can be used for machines of large output. 




Fig. 56. 



ARMATURES. 



261 



The following figure shows a good type of three bars per pole winding, 
which is simple in construction. 




Fig. 57. 



Two-phase "Winding's. — The following diagram shows a good type 
of winding for quarter-phase machines. It utilizes the winding space to 
good advantage, and is applicable to any number of coils per pole per phase. 




Fig. 58. 



Fig. 59 is a diagram of a bar winding for a quarter-phase machine, with 
four conductors per pole per phase. 
Three-phase Windings. — Fig. 60 is a diagram of a three-phase 



262 



DYNAMOS. 



winding connected in Y, in which one end of each of the three windings 
is connected to a common terminal, the other ends being connected to 
three collector rings. 




Fig. 59. 



Fig. 61 is a sample of a three-phase delta winding, in which all the con- 
ductors on the armature are connected in series, a lead being taken off to a 
collector ring at every third of the total length. 





Fig. 60. 



Fig. 61. 



In the Y windings the proper ends to connect to the common terminal and 
to the rings may be selected as follows : Assume that the conductor in the 
middle of the pole-piece is carrying the maximum current, and mark its direc- 
tion by an arrow ; then the current in the conductors on either side of and ad- 
jacent to it will be in the same direction. As the maximum ciirrent must be 
coming from the common terminal, the end toward which the arrow points 
must be connected to one of the rings, while the other end is connected to 
the common terminal. It is quite as evident that the currents in the two 
adjacent conductors must be flowing into the common terminal, and there- 
fore the ends toward which the arrows point must be connected to the com- 
mon terminal, while their other ends are connected to the remaining two 
rings. 

In a delta winding, starting with the conductors of one phase in the mid- 
dle of pole-piece, assume the maximum current to be induced .at the 
moment in this conductor; then but one-half the same value of current 
will be included at the same moment in the other two phases, and its path 



ARMATURES. 263 



and value will best be shown in the following diagram, in which x may be 

taken as the middle collector-ring, and the maximum current to be flowing 

from x toward z. It will be seen that no current 

is coming in over the line y, but part of the current 

at z will have been induced in branches b and c. 

Most three-phase windings can be connected 
either in Y or delta ; but it must be borne in mind 
that with the same windings the delta-connection 
will stand 1.732 times as much current as the Y- 

connection, but gives only — — as much voltage. 



Keating- of JLrmatures. 

Fig. 62. Path and Value 

of Current in Delta- The temperature an armature will attain during 

connected Armature, a long run depends on its peripheral speed, the 

means adopted for ventilation, the heating of the 

conductors by eddy currents, the heating of the iron core by hysteresis and 

eddy currents, the ratio of the diameter of the insulated conductor to that 

of its copper core, the current density in the conductor, the radial depth of 

winding, whether the armature is of cylinder or drum type, and the amount 

and character of the cooling surface of the wound armature. 

The higher the peripheral speed of the armature the less is the rise of 
temperature in it. Mr. Esson gives, as the result of some experiments on 
armatures with smooth cooling surfaces, the following approximate rule : 

55 W 350 W 




'■■a (i + 0.00018 V) ~ s' (i + 0.00059 vy 

where C° = difference of temperature between the hottest part of the arm- 
ature and the surrounding air in degrees, Centigrade, 
W— watts wasted in armature, 
8 = active cooling surface in square inches, 
8' ■==■ active cooling surface in square centimeters, 
Vtn peripheral speed of armature in feet per minute, 
V' = peripheral speed in meters per minute 

The more efficient the means adopted for ventilating the armature by cur- 
rents of air, the smaller is the temperature rise. Some makers leave spaces 
between the winding at intervals, thus allowing the air free access to the 
core and between the conductors. A draught of air through the interior of 
the armature assists cooling, and should be arranged for whenever possible. 
For heavy currents it is sometimes necessary to subdivide the conductors 
to prevent eddy currents ; stranded conductors, rolled or pressed hydraulic- 
ally, of rectangular or wedge-shaped section, have been used. Such subdi- 
vision should be parallel to the axis of the conductor, and preferably effected 
by the use of stranded wires rather than laminae. Few armature conductors 
of American dynamos of to-day are divided or laminated in any degree 
whatsoever. Solid copper bars of approximately rectangular cross-section 
are often used, and little trouble is found from Foucault currents. 

The power wasted by eddy currents in an armature core is proportional to 
the square of the maximum magnetic induction and to the frequency of 
change of magnetic induction in the iron. 

Mr. Kapp considers 1.5 square inches (9.7 square centimeters) of cooling 
surface per watt wasted in the armature, a fair allowance. 
Esson gives the following for armatures revolving at 3000 feet per minute. 
W= watts wasted in heat in winding and core, 
S = cooling surface, exterior, interior, and ends, in square inches, 
S/ =. cooling surface, exterior, interior, and ends, in square centimeters, 
T =z temperature difference between hottest part of armature and 
surrounding air in C°. 

m 35 W 225 W 
Then T = — =— or 



S Si 

Specifications for standard electrical apparatus for U.S. Navy say, " No 



264 DYNAMOS. 



part of the dyriamo, field, or armature windings shall heat more than 50° F. 
above the temperature of the surrounding air after a run of four hours at 
maximum rated output." 

According to the British Admiralty specification for dynamos, the tem- 
perature of the armature one minute after stopping, after a six hours' run, 
must not exceed 30° F. above that of the atmosphere. In this test the ther- 
mometer is raised to a temperature of 30° F. above that of the atmosphere 
before it is placed in contact with the armature, and the dynamo complies 
(or does not comply) with the specification according as the thermometer 
does not (or does) indicate a further rise of temperature. 

The best dynamo makers to-day specify 40° and 45° C. as the maximum 
rise in temperature of the hottest part of a dynamo, or 55° if the tempera- 
ture of the commutator surface is to be measured. 

Armature Reactions. 

In continuous current dynamos, with no special devices for reversing 
the currents in the armature sections as they successively pass under the 
brushes, it is necessary, in order to avoid sparking, to give the brushes a 
forward lead ; the lead usually varies with the output of the dynamo. 

With the forward lead given to the brushes the effect of the armature cur- 
rent is to weaken and distort the magnetic field set up by the field-magnets ; 
a certain number — depending on the lead of the brushes — of the armature 
ampere-turns directly oppose those on the field-magnets, and render a some- 
what larger number of these ineffective, except as regards wasting power ; 
the remaining armature ampere-turns tend to set up a magnetic field at 
right angles to the main field, with the result that th«j resultant field is 
rotated forward in the direction of motion of the armature, and that tbe 
field-strength is reduced in the neighborhood of every trailing pole-piece 
horn, and is increased in that of every leading pole-piece horn. When, 
therefore, the brushes have a forward lead each armature section as it 
comes under a brush enters a part of the field, of which tbe strength is 
reduced by the armature cross-induction ; and, if this reduction is great, 
the field-strength necessary for reversing the current in the section (in the 
short time that the section is short-circuited under the brush) may not be 
obtained, and sparkless collection may thus be rendered impossible. 

Various devices for reversing the currents in the armature sections, as 
they pass successively under the brushes, without giving a forward lead to 
the brushes, have been proposed ; a number of these are described in the 
paper by Mr. Swinburne ; an improvement of Mr. W. B. Sayers consists in 
interposing auxiliary coils between the joints of adjacent armature sections 
and the corresponding commutator bars. Each auxiliary coil is wound on 
the armature with a lead relatively to the two main armature sections and 
the commutator bar which it connects together. Tbe result of this arrange- 
ment is that the difference between the E.M.F.s in the two auxiliary coils 
connecting any given armature section to the two corresponding commuta- 
tor bars may be made sufficient to reverse the current in the armature sec- 
tion when short-circuited under a brush, even if the brush has a backward 
instead of a forward lead. Mr. Sayers's invention not only makes it possible 
to reduce the air-gap very considerably, but also, by enabling a backward 
lead to be given to the brushes, to make the armature winding assist that 
on the field-magnets in producing the required magnetic field for the arma- 
ture. Both these results assist in reducing the weight and excitation of the 
field-magnets. 

For a two-pole dynamo the back ampere-turns are given by the formula, 

where 6 = angular lead of brushes in degrees, 

_ZV"rr number of conductors, counted round periphery of armature, 

in series, 
/== armature current in amperes ; 

and, according to Prof. S. P. Thompson, the number of ampere-turns on the 
field-magnets required to compensate for the back ampere-turns on the 
armature is v X (A.T.)s, where v is the coefficient of magnetic leakage. 



ARMATURES. 265 



In the Thompson-Ryan dynamo the effects of armature reaction are neu- 
tralized hy a special winding through slots across the faces of the pole-pieces, 
parallel with the axis of the armature; this winding is in series with the 
armature, and the same current flowing in both, but in such direction that 
all effects on the field magnets are neutralized, the ampere-turns of the shunt 
are therefore much less than in other dynamos, there is no sparking under 
any ordinary conditions of load, the brushes are placed permanently when 
the machine is set up, and the efficiency is high under a wide range. 

This dynamo is not compound- wound in the usual meaning of the term, 
but the effects of compounding can be obtained by varying the position of 
the brushes, a backward lead, tending to raise the voltage by assisting the 
field magnets, as the current or load increases. 

Drag* on Armature Conductors. — In dynamos, each armature 
conductor has to be driven in opposition to an effort or drag proportional at 
every instant to the product of the current carried by the conductor into 
the strength of the magnetic field. This drag on a conductor varies, there- 
fore, with the position of the conductor relatively to the field-magnet poles, 
and is a maximum when the conductor passes through that part of the air- 
gap at which the magnetic induction is greatest. The arrangements for 
driving the armature conductors must, of course, be adapted to the greatest 
value of the drag to which a conductor is exposed, and this is given for 
smooth core armatures by the formula below. 

Let 1= current in amperes carried by each conductor, 

(B = maximum induction in air-gap per square centimeter, 
F=z maximum drag on a conductor in lbs. per foot of length. 

Then F = ^^ or .00000685 / <£ 

In slotted armatures the drag comes upon the core teeth instead of the 
conductors. 

Current I*ensity in Armature Conductors. — This should be 
determined so that the I 2 r loss, plus the hysteresis loss in the armature, 
does not exceed the less of the two limiting values assigned by the condi- 
tions of efficiency and freedom from overheating respectively ; in practice 
current densities of 2,000 to 3,000 amperes per square inch are common, and 
in drum armatures the current density is sometimes higher. American 
practice gives 600 to 800 circular mils per ampere. 



FIELD JIAGYETS, 

Surface necessary for Safe Temperature. 

Esson gives the following method of determining the surface necessary for 
a magnet coil to keep its heat within assigned limits. 
Let w = watts wasted in heating, 

s == cooling surf ace in square inches of coil, not including end flanges 

and interior, 
s, = same as above in square centimeters, 
t — temperature of hottest part above surrounding air, 



then 



335™ 



Maximum current = V ^f/*- F X sg~i^. 
99 x hot r 

Hot r = cold r -f 1% for each additional 4.5° F. 



266 



DYNAMOS. 
Table of Cooling- Surfaces. 



Excess temperature above sur- 
rounding air. 


Cooling surface per watt in 


F.° 


C.° 


square inches. 


sq. centimeters. 


30 
40 
50 
60 
70 


15 
20 
25 
30 
35 
40 


3.67 
3.30 
2.75 
2.48 
2.20 
1.98 
1.83 
1.65 
1.57 
1.41 
1.38 


23.7 
21.3 
17.8 
16.0 
14.2 
12.8 
11.8 
10.7 
10.1 
9.1 
8.9 



UTotes. — The number of ampere-turns necessary to overcome an air-gap 
of one-half inch equals the number of lines of force per square centimeter. 
Approximate rule by G. Forbes. 

Current Density. 

(Esson.) 

The current density per square centimeter section in the magnet winding 
of ordinary machines is about half the current density in the armature. 

Safe Continuous Output of Dynamos and IfEotors. 

(Albion Snell.) 

^ „ „ J Drums Watts = l<Pn .015. 

Dynamos j Cylinders Watts _ l(Pn <0L 

Drums Brake H.P. — ld 2 n .000015. 



Motors 



Cylinders Brake H.P. = .00001. 



I = length of armature in inches, 
d = diameter of armature in inches, 
n = number of revolutions per minute. 

Ojrostatic A < •< ion on Dynamos in Ships. 

(Lord Kelvin.) 



9 



and P = 



gi 



where 



L =. moment of couple on axis, 
P — pressure on each bearing, 
7F= weight of armature, 
k =i radius of gyration about axis, 

il =: — A — maximum angular velocity of dynamo in radians 

per second due to rolling of ship, 

A = ^r = amplitude in radians per second, 

(Radian is unit a/igle in circular measure.) 



SYNCHRONIZERS. 



267 



d = degrees of roll from mean position. 

T= periodic time in seconds. 

a) = 2nn = angular velocity of armature in radians per second. 

n z= number of revolutions of armature per second. 
I =2 distance between bearings. 

g = acceleration due to gravity. 
Note.— On applying the above formula to dynamos, where W, k, and o» 
are great, it will be found advisable to place their plane of rotation athwart- 
ships, in order to avoid as far as possible wear and tear of bearings due to 
the gyrostatic action. 



lYICHROlTIZERi. 

There are numerous methods of determining when alternators are in step, 
some acoustic, but mostly using incandescent lamps as an indicator. 

In the United States it is most common to so connect up the synchronizer 
that the lamp stays dark at synchronism ; in England it is more usual to 
have the lamp at full brilliancy at synchromism, and on some accounts the 
latter is, in the writer's opinion, the better of the two, as, if darkness indi- 
cates synchronism, the lamp breaking its filament might cause the machines 
to be thrown together when clear out of step ; on the other hand, it is some- 
times difficult to determine the full brilliancy. 

The two following cuts show theory and practice in connecting synchro- 
nizers. 



^@ 






/& 



KLTERNAXOR ALTERNATOR 

-HM 1 J — .00009 




100 V 

SYNCHRONIZING 

LAMP 



Fig. 64. Synchronizer Connections. 

Lamp lights to full c.p. when dyna- 
mos are in synchronism. 



Fig. 63. Synchronizer Connections. 

When connected as shoivn, the lamp 
will show full c.p. at synchronism. 
If a and b are reversed, darkness of 
'< lamp uiill shoiv synchronism. 

Two transformers having their primaries connected, one to the loaded 
and the other to the idle dynamo, have their secondaries connected in series 
through a lamp ; if in straight series the lamp is dark at synchronism ; if 
the secondaries are cross-connected the lamp lights in full brilliance at 
synchronism. 

Wote on the Parallel Running- of Alternators. — There is 
little if any trouble in running alternators that are driven by water-wheels, 
owing to the uniform motion of rotation. With steam-engine driven ma- 
chines it is somewhat different, owing to more cr less pulsation during a 
stroke of the engines, caused by periodic variations in the cut-off, -which 
cause oscillations in the relative motion of the two or more machines, 
accompanied by periodic cross currents. Experiments have proved that a 
sluggish governor for engines driving alternators in parallel is more desi- 



268 DYNAMOS. 



rable than one that acts too quickly ; and it is sometimes an advantage to 
apply a dashpot to a quick-acting governor, one that will allow of adjust- 
ment while running. It is quite desirable also that the governors of engines 
designed to drive alternators in parallel shall be so planned as to allow of 
adjustment of speed while the engine is running, so that engines as well as 
dynamos may be synchronized, and load may be transferred from one 
machine to the others in shutting down. Foreign builders apply a bell con- 
tact to the same part of all engines that are to be used in this way, and throw 
machines together when the bells ring at the same time. These bells would 
also serve to determine any variation, if not too small, in the speed of the 
machines, and assist in close adjustment. 

Manufacturers do not entirely agree as to the exact allowance permissible 
for variation in angular speed of engines, some preferring to design their 
dynamos for large synchronizing power, and relatively wide variation in 
angular speed, while others call for very close regulation in angular varia- 
tion of engine speed, and construct their dynamos with relatively little syn- 
chronizing power. 

Dynamos of low armature reaction have large synchronizing power, but if 
accidentally thrown out of step are liable to heavy cross-currents. On the 
contrary, machines with high armature reaction have relatively little syn- 
chronizing power, and are less liable to trouble if accidentally thrown out 
of step. 

The smaller the number of poles the greater may be the angular variation 
between two machines without causing trouble, thus low frequencies are 
more favorable to parallel operation than high ;_ and this is especially so 
where the dynamos are used to deliver current to synchronous motors or 
rotary converters. 

Specifications for engines should read in such a manner as to require not 
more than a certain stated angular variation of speed during any stroke of 
the machine, and this variation is usually stated in degrees departure from 
a mean speed. 

The General Electric Company states it as follows : — 

"We have . . . fixed upon two and one-half degrees of phase departure 
from a mean as the limit allowable in ordinary cases. It will, in certain 
cases, be possible to operate satisfactorily in parallel, or to run synchronous 
apparatus from machines whose angular variation exceeds this amount, 
and in other cases it will be easy and desirable to obtain a better speed con- 
trol. The two and one-half degree limit is intended to imply that the max- 
imum departure from the mean position during any revolution shall not 

exceed ^£- of an angle corresponding to two poles of a machine. The angle 

360 
of circumference which corresponds to the two and one-half degrees of 
phase variation can be ascertained by dividing two and one-half by one-half 
the number of poles ; thus, in a twenty-pole machine, the allowable angular 

2 1 
variation from the mean would be -f = .25 of one degree." 

Some foreign builders of engines state the conditions as follows : Calling N 
the number of revolutions per minute, the weight of" all the rotary parts of 
the engine should be such that under normal load the variation in speed dur- 

ing one revolution ^ • will not exceed — -• Some state — — • 

N average 250 200 

Oudin says : " The regulation of an engine can be expressed as a percent- 
age of variation from that of an absolutely uniform rotative speed . A close 
solution of the general problem shows that \\° of phase displacement cor- 
responds to a speed variation, or " pulsation," with an alternator of two n 
poles, as follows : — 

In the case of a single cylinder or tandem compound engine — — - 

5.5% 
A cross compound 

A working out of the problem also shows . . . that no better results are 
obtained from a three-crank engine than a two-crank. 

The Westinghouse Company designs its machines with larger synchro- 
nizing effect by special construction between poles, and allows somewhat 



ALTERNATORS IN PARALLEL. 



269 



larger angular variation, stating it as follows : The variation of the fly- 
wheel through the revolution at any load not exceeding 25% overload, shall 
not exceed one-sixtieth of the pitch angle between two consecutive poles 
from the position it would have if the motion were absolutely uniform at 
the same mean velocity. The maximum allowable variation, which is the 
amount which the armature forges ahead plus the amount which it lags 
behind the position of absolute uniform motion is therefore one-thirtieth of 
the pitch angle between two poles. 

The number of degrees of the circumference equal to one-thirtieth of the 
pitch angle is the quotient of 12 divided by the number of poles. 

Alternators in Parallel. 

To connect an idle alternator in parallel with one or more already in use : 
Excite the fields of the idle machine until at full speed the indicator shows 
bus bar pressure, or the pressure that may have been determinea on as the 
best for connecting the particular design of alternator in circuit. 

Connect in the synchronizer to show when the machines are in step, at 
which point the idle machine may be connected to the bus bars. The load 
will now be unequally divided, and must be equalized by increasing the driv- 
ing-power of the idle dynamo until it takes on its proper part of the load. 

Very little control over the load can be had from the field rheostats. 

To disconnect an alternator fron the bus bars : Decrease its driving power 
slowly until the other machines have taken all the load from it, when its 
main switch may be opened and the dynamo stopped and laid off. 

Current leads 



from brushes to binding-posts, must be ample to produce no appreciable 
drop in voltage. The following table gives current densities, etc., for brush- 
holders, cables, conductor-rods, cable-lugs, binding-posts, and switches. 

Average Current Densities for Cross-section and Contact 
Surface of Various materials. 





Material. 


Current density. 




Square Mils 
per Ampere. 


Amperes per 
Square Inch. 


1 

Cross section . y 


Copper wire . . . 
Copper rod .... 
Copper- wire cable . 
Copper casting . . 
Brass casting . . . 


500 to 800 

800 " 1,200 

600 " 1,000 

1,400 '• 2,000 

2,500 " 3,300 


1,200 to 2,000 
800 " 1,200 

1,000 " 1,600 
500 " 700 
300 " 400 


Brush contact . i 


Copper brush . . . 
Carbon brush . . . 


5,700 " 6,700 
28,500 " 33,500 


150 " 175 
30 " 35 


Sliding contact [ 


Copper — copper . . 
Brass <£££» . [ 


( 10,000 " 15,000 
j 20,000 " 25,090 


67 " 100 
40 " 50 


Screwed contact > 


Copper — copper . 

Bra^ ^ co PP er • 
Brass < brass . . 


( 5,000 " 8,000 
) 10,000 " 15,000 


120 " 200 
67 " 100 



Gano S. Dunn says, in brushes of soft carbon § square inch will stand 60 
amperes maximum. 



270 MOTORS. 



MOTORS. 
conTTmruous cuhmehtt. 

Theory. 

The revolution of a motor armature in its field develops an E.M.F. which 
is counter to or opposes the impressed E.M.F., and therefore acts like re- 
sistance to reduce the amount of current flowing ; it is called the counter 
E.M.F. 

Let E = applied E.M.F. at motor terminals, 

e = counter E.M.F., 
R = resistance of motor armature, 



then 
and 



E — 
R 



Total watts W= EI=E 



Useful watts w = el = 



R 
E-. 



or W = w + I*R 

w _ e (E — e) 



W =r w 4- watts wasted in heat, 



and 



W E(E — e) 



w _ e 
lV~E 



Now w= E I— I 2 R 

and 1-= I — = maximum value of w obtained by equating to the differ 

ential coefficient of w with respect to /. 

E 
but 1= — when the armature is standing, and no counter E.M.F. is being 

R 
developed ; therefore the maximum rate of work will be obtained when the 
efficiency is 50%, and the speed of the armature is such as to produce 



for w—EI—I^R 

but IR= E — e 

E = 2E — 2e, 

E , E 

e =2'* ndc = 2R 

and the efficiency ■— = - 

Theoretically, and neglecting all losses but the one above mentioned, the 
motor will be at its maximum efficiency when it is run at the required speed, 
and produces the required power, and e is maximum, or as nearly equal to 
E as can be obtained. 



CONTINUOUS CURRENT. 



271 



Let 

then 
and 
If 

then 



and, as 

Avhere 
and 

hence 



and 



Speed and Torque. 

to — In rev. = 2n x rev. per sec. — angular velocity. 

T= torque, 
u>T =. power (mechanical) in foot-pounds per sec, 
e /= electric power in watts. 
la = current in armature, 



w = e la = i 



5o0 550 



rev. x n x $ 

n = number of wires on the periphery of the armature, 
<t> =r flux in the armature core, 

2„Xrev.xT X )£=** XreV ' X * Xn 

550 



108 



27I-7 7 : 



la X 



550 



746 X 10 s 
Torque in pounds at 1 foot radius will then be 



T—Ia t 



-f- 13.56 X 10 7 



If <t> is constant Twill be proportional to la, and Twill be greatest, there 

E 
fore, when the armature is standing, and la = -=. 



If 


r = resistance of the armature 


then 


T E-e 
la = 


and 


2 n- ■ — — — - — 



Speed in rev. per sec 



r X 13.56 X 10 7 
T— 0, when rev. n $ = E X 10 s . 

^X10 8 2tt X T X 13.56 X r X 10 15 



n X 



$2 



If r is small and $ is relatively large, the second term may be neglected. 

The stronger the field, i.e., the $, the slower will be the speed ; and if $ is 
constant the speed is proportional to E. 



Series-Wound Motor. 

Values in C. G. S. units. 

In a series motor R— ra -\- rm where ra = resistance of the armature, and 
rm = resistance of the fields : 



Let 
and 



$ sat. = complete saturation of field magnets, 

I' = diacritical cnrrent, or current at half saturation, 



then 



= <J> sat x 



I+F 



-nrr X- ve n ® Sat - 

Writing Ffor — - — - 



T= Y -j-j--j, -r 13.56 X 10 7 = torque in pounds at 1 ft. radius. 



7=— .inC. G. S. units. 



EI 



RI* . 



2tt T 



in C. G. S. units- 



272 



MOTORS. 



In a series motor the current is the same under the same load at any 
speed. In other words, the torque is almost directly proportional to the 
current. The following curves show the speed and tut que curves lor a 
series motor on a constant potential circuit. 




TORQUE 

Fig. 65. 



Slumt- Wound Motor. 

Values in 0. G. S. units. 



rn r U * 



la — I 
<t> = <I> sat. X 



Is, where Is = current in the shunt field, 

E + E> 
tion in field magnets. 



where E' is the E M F. to give half gatura- 



=*0 



ra \ 
rs ) 



ra I. 



$ sat. X 



E 



E + E> 



and if Y 



'=? 



E-\- E' % 
E + rs 



n <*> 

a motor 



[*0+=)-~ '] 



Brushes on a motor must he set back of the neutral point, or with a 
" backward lead." This tends to demagnetize the fields, and as weakening 
the fields of a motor tends to increase the speed, the increase ot Joact on a 
shunt-wound motor tends to prevent the speed failing, and the shunt motor 
is very nearly self-regulating. 



lieonartTs System of Motor Control. 

Wherever it becomes necessary to vary the speed and torque of a contin- 
uous current electric motor to any considerable degree, any of the rheostat 
methods introduce very considerable losses, and are apt to induce bad 
sparking at the commutator. 

H. Ward Leonard, E.E., invented the method shown in Fig. 66, which 
gives most excellent results, although to some extent complicated-, and is 
aighly efficient. 

The driving motor, or rather motor which it is wished to control, is pro- 
vided with a separately excited field, which can be varied by its rheostat to 
produce any rate of speed, from just turning to the full speed of which it 
may be capable. Current is supplied to its armature from a separate gen- 
erator, and by varying the separately excited field of this generator, the 
amount of current supplied to the motor armature can be varied at will, and 
the torque therefore changed to suit the circumstances. 

The generator is driven at constant speed by direct connection to a motor 
which gets its current from an outside source, or to another generator 
driven by some other motive power, say a steam engine. This driven gen- 



ALTERNATING CURRENT MOTORS. 



273 



erator supplies current for exciting the fields of the secondary generator 
and main motor. 

By reversing the field of the generator, the current in its armature is 
reversed, and therefore so is the direction of rotation of the motor armature. 

Fig. 67 shows the Leonard system adapted to electric street railway motor 
control. 




FIG. 66. 



Leonard's System of Motor 
Control. 



Fig. 67. Leonard's System of 
Electric Propulsion. 



AtTEHMATiarCJ CURKEBfT IVEOTORS. 

While the single-phase alternating current motor has been quite well de- 
veloped during the last few years, it has as yet come but little into use, 
OAving largely to its inductive effect on the line, and poor efficiency and un- 
satisfactory operation. On the contrary, the multiphase motor has been so 
far developed as to bring it into very strong competition with the direct 
current motor, owing probably to its extreme simplicity, lacking all brushes, 
commutators, and other troublesome attachments. 




CURRENT END uuhhlnj. lnu 

Fig. 68. Connections for Standard 
S. P. A. C. Motor of the Fort 
Wayne Electric Corporation. 

Only the most elementary formula; will be given here, and the reader is 
referred to the numerous books treating on the subject ; among others, 
S. P. Thompson, Steinmetz, Jackson, Kapp, and others. 

Following is a statement of the theory of the multiphase motor, condensed 
from a pamphlet of the Westinghouse Electric and Manufacturing Company. 



274 MOTOKS. 

Elementary Theory of the Multiphase Induction Motor. 

If a horse-shoe magnet be held over a compass the needle will take a posi- 
tion parallel to the lines of force which flow from one pole to the other. 
It is perfectly obvious that if the magnet be rotated the needle will follow. 

If a four-pole electromagnet be substituted for the horse-shoe, and current 
be made to flow about either one of the sets of poles separately, the needle 
will take its position parallel with the lines of force that may be flowing, as 
will be seen by the following figures. 





Fig. 69. 



Fig. 70. 



If the two sets of poles are excited at the same time by currents of equal 
strength, then the needle will take its position diagonally, half way be- 
tween the two sets of poles, as Avill be seen by the following diagram. 

It is now easily conceivable that if one of these currents is growing 
stronger while the other is at the same time 
becoming weaker, the needle will be at- 
tracted toward the former until it reaches 
its maximum value, when if the currents 
are alternating, the strong current having 
reached its maximum begins to weaken, 
and the other current having not only re- 
versed its direction but begun to grow 
strong, attracts the needle away from the 
first current and in the same direction of 
rotation. If this process be continually 
repeated, the needle will continue to re- 
volve, and its direction of rotation will be 
determined by the phase relation of the 
two currents, and the direction of rotation 
can be reversed by reversing the leads of 
one phase. 

If the compass needle be replaced by an 
iron core wound with copper conductors, 
secondary currents will be induced in 

these windings, which will react on the field windings, and rotation will 
be produced in the core just as it was in the compass needle. Two cranks 
at right angles on an engine shaft are analogous with the quarter-phase 
motor, and three to the three-phase motor, which depends on the same 
principle for its working. 




Fig. 71. 



Theory of Multiphase Induction J?f otor. 

Condensed from C. P. Steinmetz. 

The following names and symbols are used for designating the parts and 
properties of the induction motor : — 



ALTERNATING CURRENT MOTORS. 275 



Stator =. stationary part, nearly always corresponding to the field. 
Motor = rotating part, corresponding' to the armature of the d.c. motor. 
D, — angular speed of the rotating magnetic field = 2w rev. -J- m, where 

m = number of pairs of poles. 
to = angular speed of rotor = 2n rev. 2 -f- m, where rev. 2 = number of rev- 
olutions per second. 
T = torque between the stator and rotor. 



Analytical Theory of Polyphase Induction motors. 

Let r = resistance per circuit of primary. 

r, — resistance per circuit of secondary , 
being reduced to primary system by square of the ratio of turns. 

Let d = number of poles, 

x = reactance of primary, per circuit, 
x, = reactance of secondary, per circuit, 

reduced to primary system by square of the ratio of turns. 

Let S =. per cent of slip, 

/= current per circuit of primary. 
E = applied E.M.F. per circuit, 
Z = impedance of whole motor per circuit, 
jST= frequency of applied E.M.F. 

Let the primary and secondary consist of p. circuits oaaj). phase system. 

n = primary turns per circuit, 
n y = secondary turns per circuit, 

Let 

n, 

Then 

S E 
/(neglecting ex. current) 



Torque T = 

Power = 

Max. torque = 



dpr,E* S 

4tt & [(TV + Sr)* -f S 2 {x, + a;)^] 

p r, E 2 S (1 — S) 
(r, -f Sr) 2 + S 2 {x, + x) 2 

dp E 2 

8tt jV \r + V r * + (x, + x) 2 ] 



Max. power = — — | v —== at the slip S = —=, 

2[r + r, + Z] * r, + Z 

E 
Starting current = i = -^ 

~. .. dpE 2 r. 

Starting torque = — — ■=■ X -^ 

Note that the maximum torque is independent of secondary resistance r y , 
and thus the speed at maximum torque depends on the secondary resistance. 
Current at maximum torque is also independent of secondary resistance. 

The maximum torque occurs at a lower speed than the maximum output. 
A resistance can be chosen that when inserted in the secondary, the maximum 



276 



MOTORS. 



torque will be obtained at starting ; that is, the speed at which, maximum 
torque occurs can be regulated by the resistance in the rotor. 




9o SYNCHRONISM 



Fig. 72. Torque curves for Polyphase Induction Motor. 



Curves 1, 2, and 3 show the effect of successive increases of rotor resist- 
ance, rotor run on part of curve a — b ; for here a decrease of speed due to 
load increases the torque. 

Speed of Induction Miotor. — The speed or rotating velocity of 
the magnetic field of an induction motor depends upon the frequency 
(cycles per second) of the alternating current in the field, and the number 
of poles in the field frame, and may be expressed as follows : — 

rev. = revolutions per minute of the magnetic field, 
p = number of poles, 
/= frequency; then 



rev. r= 120 



/ 



The actual revolutions of the rotor will be less than shown by the formula, 
OAving to the slip which is expressed in a percentage of the actual revolu- 
tions ; therefore the actual revolutions at any portion of the load on a 
motor will be 

rev. X slip due to the part of the load actually in use. 
actual speed = rev. (1 — % of slip.) 

The following table by Wiener, in the American Electrician, shows the 
speeds due to different numbers of poles at various frequencies. 



Speed of Motary field for Different Numbers of Poles 
and for Various frequencies. 



o 


Speed of Revolving Magnetism 


in Revolutions per Minute, when 








Frequency is : 








a ° 


25 


30 


33| 


40 


50 


60 


66| 


80 


100 


120 


125 


133J 


2 


1500 


1870 


2000 


2400 


3000 


3600 


4000 


4800 


6000 


7200 


7500 


8000 


4 


750 


900 


1000 


1200 


1500 


1800 


2000 


2400 


3000 


3600 


3750 


4000 


6 


500 


600 


667 


800 


1000 


1200 


1333 


1600 


2000 


2400 


2500 


2667 


8 


375 


450 


500 


600 


750 


900 


1000 


1200 


1500 


1800 


1875 


2000 


10 


300 


360 


400 


480 


600 


720 


800 


960 


1200 


1440 


1500 


1600 


12 


250 


300 


333 


400 


500 


600 


667 


800 


1000 


1200 


1250 


1333 


14 


214 


257 


286 


343 


428 


514 


571 


686 


857 


1029 


1071 


1143 


16 


188 


225 


250 


300 


375 


450 


500 


600 


750 


900 


938 


1000 


18 


1(37 


200 


222 


267 


333 


400 


444 


533 


667 


800 


833 


889 


20 


150 


180 


200 


240 


300 


360 


400 


480 


600 


720 


750 


800 


22 


136 


164 


182 


217 


273 


327 


364 


436 


545 


655 


682 


720 


24 


125 


150 


167 


200 


250 


300 


333 


400 


500 


600 


625 


667 



ALTERNATING CURRENT MOTORS. 



277 



Slip. — The slip, or difference in rate of rotation between rotating field 
and rotor, is due to the resistance opposed to rotor current. 

Slip varies from 1 per cent in a motor designed for very close regulation 
to 40 per cent in one badly designed, or designed for some special purpose. 

"Weiner gives the following table as embodying the usual variations : 



Slip of Induction Motors. 







Slip, at full load, per cent. 


Capacity of Motor, H.P. 














Usual limits. 


Average. 


i 


20 


to 40 


30 


i 


10 


" 30 


20 


h 


10 


" 20 


15 


1 


8 


" 20 


14 


2 


8 


" 18 


13 


3 


8 


" 16 


12 


5 


7 


" 15 


11 


n 


6 


" 14 


10 


10 


6 


" 12 


9 


15 


5 


" 11 


8 


20 


4 


" 10 


7 


30 


3 


" 9 


6 


50 


2 


" 8 


5 


75 




" 7 


4 


100 




" 6 


3.5 


150 




" 5 


3 


200 




" 4 


2.5 


300 




" 3 


2 



Core of Stator and Rotor. — Both the field-frame core, or Stator, 
and the armature core, or Botor, are built up of laminated iron punchings in 
much the same manner as are the armature cores of ordinary dynamos. 

The windings in both cases are laid in slots across the face of either part, 
and for this reason both parts are punched in a series of slots or holes for 
the reception of the windings. The following cuts, taken from the " Ameri- 
can Electrician," show the usual form of slots used. 




Figs. 73 and 74. Forms of Punchings of Induction Motors. 



The number of slots in the stator must be a multiple of the number of poles 
and number of phases, and Weiner gives the following table, in the " Ameri- 
can Electrician," as snowing the proper number to be used in various cases, 
both for two- and three-phase machines. In practice the number of poles 
is determined by the speed required and the available frequency ; then the 
number of slots is so designed as to be equally spaced about the whole inner 
periphery of the stator. 



278 MOTORS. 

N'liml.MT of fclofs in Jfi«'8«l- Frame of Induction Ulotors. 



Capacity of Motor. 


Number of 
Poles. 


Slots per 
Pole. 


Slots per Pole per Phase. 


Two-Phase. 


Three-Phase. 


£ H.P. to 1 H.P. 


4 to 8 


3 

4 


l h 


1 


i H.P. to 1 H.P. 


4 to 6 


5 
6 


2i 
3 


2 




4 to 10 


5 
6 


3 


2 


2 H.P. to 5 H.P. 


4 to 6 


7 
8 
9 


' f 


3 


6 H.P. to 50 H.P. 


6 to 12 


7 
8 
9 


? 

4£ 


3 


4 to 8 


10 
11 
12 


5 
6 


4 




10 to 20 


7 
8 
9 


? 

4§ 


3 


50H.P.to200H.P. 


8 to 12 


10 
11 
12 
13 


5 


4 




6 to 10 


14 
15 
16 


? 


5 



The number of slots per pole per phase in the rotor must he prime to that 
of the stator in order to avoid dead points in starting, and to insure smooth 
running, and commonly range from 7 to 9 times the number of poles, or 
any integer not divisible by the number of poles, in the squirrel cage or 
single conductor per slot windings. The proper number of slots may be 
taken from the following table by Weiner : 



ALTERNATING CURRENT MOTORS. 



279 



H umber of Rotor Slots for Squirrel-Cag*e Induction Motors 
up to 5» H.I*. Capacity. 



Number 

of 
Poles, p. 


Limits of Slots, 
Number 
7 p. to 9 p. 


Number of Rotor Slots. 


4 
6 

8 


28 to 36 
42 " 54 

56 " 72 


29, 30, 31, 33, 34, 35, 37. 

43, 44, 45, 46, 47, 49, 50, 51, 52, 53. 

57, 58, 59, 60, 61, 62, 63, 65, 66, 67, 68, 69, 70, 71. 



In large machines, where there is more than one conductor in each slot 
and in which the winding is connected in parallel, the number of slots in 
the rotor must be a multiple of both the number of phases and the number 
of pairs of poles. 

The following table gives numbers of slots for various field-slots : 

lumber of Rotor-Slots for Induction Motors of Capacities 
over 5 H.P. 



Number of 

Field-Slots per 

Pole. 



Number of Rotor-Slots. (n 8 = number of 
Field-Slots.) 




fn 8 . 


or § n 8 


1 n«. 




£ n 8 . 


" | n 8 


|IU. 


" §n« 


flls. 


" §n« 


f ns- 


" §n 8 


|n 8 . 


" |n„ 



Hux Density. — This must be settled for each particular case, as it 
will be governed much by the quality of iron and the particular design of 
the motor. 

Hysteresis loss increases as the 1.6 power of the flux density ; and eddy 
current losses are proportional to the square of the density and also to the 
square of the frequency. 

The following table shows practical values : 

ITlux-Rensities for Induction Motors. 

(Wiener.) 





Flux-Density, in Lines of Force per Square Inch. 


Capacity 

of 

Motor, 

H.P. 


For Frequencies 
from 25 to 40. 


For Frequencies 
from 60 to 100. 


For Frequencies 
from 120 to 180. 




Practical 
Values. 


Aver- 
age. 


Practical 

Values. 


Aver- 
age. 


Practical 
Values. 


Aver- 
Age. 


i 


12000 to 18000 
15000" 25000 
18000 " 32000 


15000 
20000 
25000 


10000 to 15000 
12000 " 18000 
15000 " 25000 


12500 
15000 
20000 


7000 to 11000 
7500 " 12500 
8000 " 17000 


9000 
10000 
12500 



280 



MOTORS. 



ITluX'Rensities for Induction Motors —(Continued). 





Flux-Density, in Lines of Force per Square Inch. 


Capacity 


For Frequencies 


For Frequencies 


For Frequencies 


Motor, 


from 25 to 40. 


from 60 to 100. 


from 120 to 180. 


H.P. 














Practical 


Aver- 


Practical 


Aver- 


Practical 


Aver- 




Values. 


age. 


Values. 


age. 


Values. 


age. 


1 


20000 to 40000 


30000 


18000 to 32000 


25000 


9000 to 21000 


15000 


2 


25000 " 45000 


35000 


20000 " 40000 


30000 


10000 " 25000 


17500 


5 


30000 " 50000 


40000 


25000 " 45000 


35000 


11000 " 29000 


20000 


10 


40000 " 60000 


50000 


30000 " 50000 


40000 


12500 " 32500 


22500 


20 


50000 " 70000 


60000 


35000 " 55000 


45000 


15000 " 35000 


25000 


50 


60000 " 80000 


70000 


40000 " 60000 


50000 


17500 " 37500 


27500 


100 


70000 " 90000 


80000 


45000 " 65000 


55000 


20000 " 40000 


30000 


150 


80000 " 100000 


90000 


50000 " 70000 


60000 


25000 " 45000 


35000 


200f 


90000 " 110000 


100000 


60000 " 80000 


70000 


30000 " 50000 


40000 



t And over. 

In the earlier induction motors it was considered the most efficient method 
to connect the driving current to the revolving part or rotor; and as it is 
highly important that 
the number of windings 
on the rotor be prime to 
tbat of the stator, Fig. 75 
shows a winding with an 
odd combination of con- 
ductors, being 51, or three 
times 17. 

The stator windings 
would then be bars, con- 
nected at either end to a 
heavy copper ring, this 
forming a sort of " squir- 
rel-cage." 

In the modern ma- 
chines the winding 
shown would be in coils 
on the stator, the three 
ends being carried to 
terminal blocks on the 
outside of the machine 
instead of to rings as 
shoAvn,and the " squirrel- 
cage" would then be 
placed on the rotor and 
be made of bars as men- 
tioned. 

Starting* and Reg-- 




FlG. 75. 



ulating- Devices. — Small induction motors, up to about 5 h. p. capa- 
city, are started by closing the circuit directly to the motor. In large ma- 
chines this would not be safe, as the rotor is standing, and would act in a 
lesser degree as the short-circuited secondary of a static transformer, and 
cause a heavy rush of current. 

Resistance in Rotor. —This is a favorite method with the General 
Electric Company. A set of strongly constructed resistances is secured 
inside the rotor ring, and so arranged with a lever that they may be closed 
or short-circuited after the motor has reached its full speed. These resist- 



SYNCHRONOUS MOTORS. 281 

ances are in the armature circuits. In order to give maximum starting torque 
total armature resistance should be 

r, - Vr* + {x, + y)* 
Where r t = rotor resistance per circuit reduced to field system. 
x 1 = rotor reactance per circuit reduced to field system. 
r = resistance per field circuit. 
y = reactance per field circuit. 

This method serves the double purpose of keeping down the starting cur- 
rent and increasing the starting torque. 

Resistances in Stator. — Resistance boxes may be connected in the 
circuits supplying induction motors ; three separate resistances in three- 
phase circuits, and two separate resistances in two-phase circuits. They 
must be all connected in such a manner as to be operated in unison. Under 
these conditions the pressure at the field terminals is reduced, as is of course 
the starting current and the starting torque. In order to start a heavy load, 
under this arrangement, a heavy starting-current is necessary. 

Compensators or Auto-Transformers. — This method is greatly 
favored by the Westinghouse Electric and Manufacturing Company, is used to 
some extent by the General Electric Company, and consists of introducing an 
impedance coil across the line terminals, the motor being fed, in starting, 
from some point on the winding where the pressure is considerably less 
than line pressure. This avoids heavy drafts of current from the line, thus 
not disturbing other appliances attached thereto, but as regards starting- 
current and torque has the same effect as resistances directly in the line ; 
that is, greatly reduces both. 

Rotor Windings Commutated. — In this arrangement all or a 
part of the rotor windings are designed to be connected in series when 
, starting, and are thrown in parallel after standard speed is attained. 
Another design has part of the conductors arranged in opposition to the 
remainder in starting, but all are thrown in parallel in regular order when 
running at standard speed. These commutated arrangements have not 
been much used in the United States. 

SYNCHRONOUS MOTORS. 

Alternators are convertible into motors ; and one alternator will run in 
synchronism with another similar machine after it is brought to the same 
speed, or, if of unlike number of poles, to some multiple of the speed of the 
driven dynamo, provided the number of pairs of poles on the motor is 
divisible into the multiple. Such motors will run as if geared to the driven 
dynamo even up to two or three times its normal full torque or capacity. 
Single-phase synchronous motors have no starting-torque, but synchronous 
motors for multiphase circuits will come up to synchronism without much 
load, giving about 25 % starting-torque, starting as induction motors, with 
the d. c. field open. 

When connected to lines on which are connected induction motors that 
tend to cause lagging currents and low-power factor of the line, over excita- 
tion of the synchronous motor fields acts in the same manner as a condenser 
introduced in the line, and tends to restore the current to phase with the 
impressed E.M.F., and therefore to do away with inductive disturbances. 

It is necessary to provide some source from which may be obtained con- 
tinuous current for exciting the fields of the synchronous motor ; and this is 
oftenest done by the use of a small d. c. dynamo belted from the motor- 
shaft, the exciting current not being put into use until the motor armature 
reaches synchronism. 

In starting a synchronous motor the field is open-circuited, and current is 
turned on the armature. In practice, field coils are connected in various ways 
to obviate the dangers of induced voltage, and a low resistance coil similar 
to the series winding of the d. c. machine is sometimes so arranged on the field 
poles as to give the necessary reaction for starting. Another way is to use 
a low-pressure excitation, and therefore few turns on the field coils ; also 
the field coils are " split up " by a switch at starting. The field excitation is 
thrown on after the rotating part approaches synchronism, which may be 
indicated by a lamp or other suitable device at the operating switchboard. 

Considerable care must be exercised in the use of synchronous motors, and 
their best condition is where the load is quite steady, otherwise they intro- 



282 



MOTORS. 



duce inductive effects on the line that are quite troublesome. The field of 
such a motor can be adjusted for a particular load, so there will be neither 
leading nor lagging current, but unity power factor. If the load changes, 
then tne power factor also changes, until the field is readjusted ; if the load 
has been lessened the current will lead, and if it increases the current will 
lag. If induction motors are connected to the same line, with a synchro- 
nous motor that has a steady load, then the field of the synchronous motor 
can be over-excited to produce a leading current, which will counteract the 
effect of the Lagging currents induced by the induction motors. If two or more 
synchronous motors are connected to the same circuit, and the load on one 
of them is quite variable, and its field is not changed to meet such changing 
conditions, a pumping effect is liable to take place in the other motors, unless 
especial provision has been made in the design of the motors to prevent it. It 
is only necessary to arrange one of the motors of the number for preventing 
this trouble, but better to make all alike. A copper shield between pole- 
pieces, and covering a portion of the pole-tip, will prevent the trouble ; and 
the Westinghouse Electric and Manufacturing Company use a heavy copper 
strap around each pole-piece, with a shoe covering part of the pole-tip In 
the air-gap. 
Theory of the synchronous motok. 





Fig. 76. 



Let R = resistance of whole circuit. 

L = self-inductance of whole circuit. 





^0 resultant. 



Fig. 77. 

Take the origin at 0. 
Let E represent maximum value. 

e ■= instantaneous value, 
e x = E l sin (pt. + </>), 
e 2 = E 2 sin (pt. — $), 
where p := 2tt n, and n number of complete periods per second. 

e = E sin (pt. — \j/) 
where i// = angle of lag of E n with respect to the origin. 
E 2 = E^+ E 2 2 -f- 1E X E 2 cos 2 0, 

E x — E 2 



For 



E 2 >E, 



Ef, leads, 
E n lags, 



COS \p 



COS (f> 



Ea Et . , 

tan ^ = jf-TTB tan * 

(E* + E 2 ) 
sin ip = V -^ J T — - cos 4 



E n and <f> are known. 



SYNCHRONOUS MOTORS. 



283 



Energy. Shifts the origin hy the angle >//. 

e x = E y sin (pt. + + $). 
e, = ^ 2 sin (pt. — 4> + »A). 

Now /= ft — — 

and / lags behind i? by the angle 6 where 

tan 5 = -+- • 

By introducing the angle i// Ave are referring the E.M.F.'s of both machines 
to the zero point of the resultant wave as origin. 
In general 

T 
eidt— E T 



where 



Let 



if: 



cos © 



w = the energy in watts, and 

© = lag or lead of / with respect to E. 

E and / are maximum values. 

T= — , or the periodic time. 
n 

<a x ■= energy given to the circuit by the generator, 
o 2 = energy absorbed from the circuit by the motor. 



"=7 J/*' 



dt 



§ , E ° cos (0 + * + 5 

\i — I sin (pt — 6)] 

*i = ^ r > ^° [cos (0 + >/,) cos 6 - 

sin (0 -f- 1//) sin 5] 



sin 6 = 



E,E n 



cos 5 



, ' , " 1 T 2(j/^i g | ^co S (^, + ^)-ii 3 sin(0 + ^) j 
and substituting — <£ for -f- we get 



(#1 + ^2) 



cos (// 



Now sin i|/ = 

^ t — ^ 

Substituting and reducing 

1 tf. 



Wa = 2 R* + p 2 L * \ El {R COS 2 * + ^ Sin 20) _jB2 * 
An angle (ft 1 is introduced such that 

T? 

sin 2 4) 1 — 



Vr2+ P *L2 



cos 2£» 



Z» 



^R*+p* L 2 



284 



MOTORS. 



Substitute in 



and 
1 



'■ - | E t Vi?2 + .p*Z* s in(2</, + 2 



a>2_ 2 B?-\-x? L? \ 

a), is a maximum when 



i)-^ 



2 <#>-{- 2 



90° or 




that is, the " sine term " = unity. 
w 2 is positive provided 
E\ \ It 

which shows that it is possible to have E 2 greater than E x if there is the 
proper ratio of resistance and reactance in" the circuit. 

Now, if we plot from an actual motor the 
armature current and the field excitation we 
get a curve shown in Fig. 79. 

This shows that the armature current '<* 

varies with the excitation for a given load. -^ 

The flatter curves are for increase of load. 5 

Point a shows under excitation, < 

b shows over excitation, = 

c shows the excitation which ** 

makes the power factor unity ; it is well 

from the point of stability of operation to 

slightly over excite, and this makes E 2 >E 1 , MtLU ' 

and also counteracts the inductive drop in Fig. 79. 

the line, thus showing that the action of an 
over excited synchronous motor is similar to a condenser. 
Graphical treatment. 

Eg = generator E.M.F. 
Em = motor E.M.F. 
Eo == resultant E.M.F. 
Io ■=. resultant current. 
O Ig=z projection of Io on O Eg. 
O Im = projection of Io on O Em. 
O I g . O Eg = u)g= energy given up by 

the generator. 
O Im . OEm = o)mz= energy absorbed by 
the motor from the cir- 
cuit. 
aim is negative, which shows that com is the 
motor, because it is taking energy from 
the circuit ; and similarly w g is the gener- 
ator, because Eg . O I g is positive, and 
gives up energy to the circuit. 

[For further discussion see Jackson's 
Alternating Current and Alternating Cur- 
rent Machines; also Electrical World for 
March 30 and April 6, 1895, by Bedell and 
Ryan. The latter is the classic paper on the subject.] 




MOTOR GEIVERAIORS OR DTUAMOTORI. 



These are of two styles, one for transforming continuous current of one 
voltage into continuous current of a different voltage, and usually called in 
America motor-generators ; the second class transforms alternating current 
into continuous current, or vice versa, the voltage not being changed except- 
ing from A.C. Vmean 2 values to d.c. values equal to the top of the A.C. wave ; 
these latter machines are now called rotary converters, and are largely used 
in connection with the circuits of the Niagara Falls Power Company and 
other power transmission stations. 



DYNAMOTORS. 285 

Motor-generators are now largely used in telegraph offices for reducing the 
pressure of the supply current to voltages suitable for use in telegraphy 
and for ringing and charging generators in telephone offices. 

Theory. Let 

E z= voltage at motor terminals. 

e = voltage at generator end terminals. 

/ = current in motor armature. 

r = resistance of motor armature. 

n — number of conductors in motor armature. 

1^ =r current in generator armature part. 

r a = resistance of generator armature part. 

n x = number of conductors in generator armature part. 

— = k — coefficient of transformation. 

E = induced E.M.F. in motor part. 
E) = induced E.M.F. in generator part. 
E = rev. x n x <t>. 
E y = rev. = ?i t X <f>. 
E — E — r I 
E 1 = e + r l I 1 . 
ke = E — r I— kr x I x . 
If it be assumed that losses by hysteresis and eddy currents be negligible, 
or that E I '= E x I x whence I r = k I, then 

Such machines run without sparking at the commutator, as all armature 
reactions are neutralized. 



Continuous Current Boosters. 

This is a type of motor generator much in use for raising or lowering the 
pressure on long feeders on the low-pressure system of distribution, and is 
to be found in most of the larger stations of the Edison companies. It is 
also much used in connection with storage-battery systems in charging cells. 

The " booster " consists of a series generator driven by a motor direct con- 
nected to its armature shaft. The terminals of the generator are connected 
in series with one leg of the feeder ; and it is obvious that the current in the 
feeder will excite the series field just in proportion to the current flowing, 
provided the design of the iron magnetic circuit is liberal enough so that 
the field is way below saturation (on the straight part of the iron curve way 
below the knee). As the armature is being independently rotated in this field, 
it will produce an E.M.F. approximately in proportion to such excitation, 
which E.M.F. will be added to that of the feeder or will oppose that E.M.F., ac- 
cording as the terminal connections are made. On three-wire systems two 
generators are direct connected to one motor, and for convenience on one 
bed-plate. 

Such a booster can be so adjusted as to make up for line loss as it in- 
creases with the load. 

One danger of a booster that is not always taken into account is. that if 
the shunt of the driving-motor should happen to open, or, in fact, anything 
should happen to the driving-motor that would result in its losing its power, 
the generator would immediately become a series motor, taking current 
from the line to which it is connected, and by its nature would reverse in 
direction of rotation, and increase in speed enormously, and if not discon- 
nected from its circuits in time would result in a complete wreck of the 
machine. It is always safest to have the generator terminals connected to 
their line through some automatic cut-out, so arranged that should 
the shunt break, as suggested, it would actuate the device, and automati- 
cally detach the booster from the circuit before harm could be done. 



286 



MOTORS. 
ROTARY COWVEHTMllS. 



A rotary converter is the name given to a machine designed for changing 
alternating currents into continuous currents. If the same machine be 
used inverted, i.e., for changing continuous currents into alternating, it is 
sometimes known as an inverted converter. Again, if the same machine be 
driven by outside mechanical power, both alternating and continuous cur- 
rents may be taken from it, and it then becomes known as a double current 
generator. 

Theoretically the rotary converter is a continuous current dynamo with 
collector rings added, which are connected by leads to certain parts of the 
armature windings, sometimes at the commutator segments. 

In the following figure, which represents in diagram the single-phase 
rotary converter, the collector rings r and r x are connected by leads to dia- 
metrically opposite segments or coils of the armature at c and c t . It is 
obvious that as the armature revolves the greatest difference of potential 
between the rings, or maximum E.M.F., will be at the instant the segments 
c and Cj pass under and coincide with the brushes B and B x ; and this 
E.M.F. will decrease as the rotation continues, until the lowest E.M.F. 
will occur when the segments c and c x are directly opposite the centre of 
the pole-pieces P and P v 




SINGLE PHASE ROTARY CONVERTER 

Fig. 81. 



The maximum alternating E.M.F. will be equal to the continuous cur- 
rent voltage at the brushes B and B x , and if the machine be designed to 
produce a sinusoidal curve of E.M.F., then the alternating E.M.F., that is, 
the Vmean 2 or effective E.M.F., will be, 



Where 



e = E sin 2n Nt. or e = - - = .707 E 

V2 

e = Vmean 2 or effective voltage, 
E =: continuous current voltage, or maximum, 
Nt = frequency of rotation. 



[n a bipolar machine the frequency is t, and in a machine with p poles the 
frequency av ill be ^ t. 

Neglecting losses and phase displacement the supply of alternating cur. 
rent to the rings must be 1^2= 1.414 / where lis the continuous current 
output. 

If, as shown in Fig. 82, another pair of rings be added, and connected to 
points on the winding at right angles to the first, then another and similar 



ROTARY CONVERTERS. 



287 



E.M.F. will be produced, but in quadrature to the first. The E.M.F. will be 
the same for each phase as in the single-phase connection previously shown, 
and still neglecting phase displacement and losses the current will be for 
each of the two phases 



V^ 



== .707 /. 




TWO PHASE, OR QUARTER PHASE 
ROTARY CONVERTER 

Fig. 82. 



If three equidistant points on the armature windings be connected to 
three rings, as shown in the following diagram, a three-phase converter is 
produced. 




THREE PHASE ROTARY CONVERTER 

Fig. 83. 

As the connections of a three-phase rotary are always delta, the E.M.F.'s 
as compared with the continuous current E.M.F. E have the following 
value : 

E 
Voltage between collector ring and neutral point e ■=. — — = .354 E. 

2V 2 



Voltage between collector rings e 1 =r 






.612 E. 



IE 2/V2 
Alternating current input = i = - — — — : - — = .943 1. 



Steinmetz, in the Electrical World of Dec. 17, 1898, gives the following 
table of values of the alternating E.M.F. and current in units of continuous 
current. 



288 



MOTORS. 







>* 












cp 


8 




biS 




IfciS 


8 


si 

A 

& 


ii 

i|(M 




CO 


CN 1 


> "3 




H> 


" 


> 




1 8 






T* 












lO 








i 




CO 










cp 

02 


li 


co 


eo 


m 


1b 


CO 


8 


3 


^ 


A 


||CN 








H 


ft 


1 CM 










CP 


S3 


CO 




<N 

55 




co 
c3 


II 

||<N 


li 

ilCN 


ii 


li 






H* 


1 <M 


|<N| 








-# 












« 




o 




6 


6 

to 


ii 


>c 


^ 


l© 


H 


c« 

ft 


li 


II 


II 




-i* 


rH UN 


l> 


iH ICN 






s 


N 


CO 


LO 


i 


6 


eo 


CO 


o> 


LO 


<p 


CO 

e3 


li 


ii 


II 


II 




ft 


IP 


|CO ||<N 


|'CN 


|<N ||CO 


H> 


> > 


> " 


> > 






1 (M 


1 IN 


<N 1 


CN 1 CO 


CP 


6 


3 

eo 


1 


"* 

** 








II 

IF 








r 5c 




II 


II 


II 


5 


ft 


-II? 


I'M 
> 


> 


co 












=1 












O 


CP 










o 


u 
u 
3 
O 


1-1 


r "' 


1-1 


i-( 


o 
















o fl. 

v ci • 


cS cp 


CP 


CP 
cp CO 
















55 W>fl 






©3 






£.2o 

£ U ft 


CP 
ft 


^43 
CP 








"55 jj e. 


CO 
CP 


to O 

CP c« 






o .3 


-° S d 


s- 


**'3t 






CO ■*-> d 


CP 


<X>"3 






O^ CI 


«»h 


ft 


ft=« 






"3 


i 


a 






> 


f> 




<3 


<i. 



ROTARY CONVERTERS. 



289 



The values of E.M.F. and of current stated above are theoretical, and are 
varied in practice by reason of drop in armature conductors and phase 
displacement. In converting from a.c. to d.c, if the current in the rotary 
is in phase with the impressed E.M.F. , armature self-induction has little 
effect ; but with a lagging current, which may be due to under-excitation, 
the induced d.c. E.M.F. is somewhat reduced; and if the machine be over- 
excited, thus producing a leading current, the induced d.c. E.M.F. will be 
raised. The same is the case in converting from d.c. to a.c, the a.c. volts 
being down on a lagging circuit. 

The corrections for the theoretical ratios of voltages as shown are, first 
for drop in the armature ; and second, they have to be multiplied by the 
factors shown above. 

Steinmetz says that the current flowing in the armature conductors of a 
rotary is the difference between the alteimating current input and the con- 
tinuous current output. The armature heating is therefore relatively small, 
and the practical limit of overload is limited by the commutator, and is 
usually far higher than in the continuous current generator. 

In six-phase rotaries the I' Z R losses of the armature are but 29 % of the 
regular I' 2 R loss in the armature as used for d.c. dynamo. 

Kapp shows that width of pole-face has a bearing on the increase in out- 
put of a rotary converter over the same machine used as a continuous cur- 
rent dynamo. He compares the output of two converters, one in which 
the pole-face is two-thirds the pole distance, and another in which it is one- 
half the pole distance. In single-phase converters the output is not equal 
to that of the d.c. dynamo, and two- and three-phase machines are much 
different. 

He gives, in the following table, the percentage of d.c. output of what 
would be the output of the same machine used as a d.c. dynamo. 





Pole-width. 




§ 


5 


rcos = i 

Single-phase J gj = ;| ; ; ; ; ; ; ; ; ; ; 
LCos= .7 


88% 
81 
73 
63 


95% 
88 
80 
70 


(Cos = l 

Three-phase \ Cos = .9 

( Cos — .8 


138 
128 
117 


144 
137 
126 






Two-or (2° S = 1 o •'■•■• 

four-phase j^s= .8 '.'.'.'.'.'.'.'..'. 


167 
160 
144 


170 
167 
153 







To find the voltage required between collector rings on rotary con- 
verters, when 

■Fes number of turns in series between collector rings, 
n = flux from one pole-piece into the armature, 
n — cycles per second, 
E =. required E.M.F. 



Then 



For single-phase and two-phase machines 

.Ess 2.83 Tw$10- 8 , 
For three-phase machines 

jS 1 — 3,69 rn'flO- 8 . 



290 MOTORS. 

The single-phase rotary has to he turned up to synchronous speed hy some 
external power, as it will not start itself. 

The polyphase rotary will start itself from the a.c. end, hut takes a tre- 
mendous lagging current, and therefore, where possible, it should he started 
from its d.c. side. 

The starting of rotaries that are connected to lines having lights also con- 
nected, should always be done from the d.c. side, as the large starting cur- 
rent taken at the moment of closing the switch will surely show in the 
lamps. Polyphase rotaries are sometimes started, as are induction motors, 
by use of a " compensator." 

In starting a rotary, the field circuit must be opened until synchronism is 
reached, after which it is closed. The d.c. side must also be disconnected 
from its circuit, as it is obvious that the current produced is alternating 
until synchronism is reached. Care must be taken to keep the field circuit 
closed when the d.c. side is connected in parallel with other machines, and 
the a.c. side open, or the armature Avill run away and destroy itself. 

As the change in excitation of the field of a rotary changes the d.c. voltage 
but little, and on the other hand produces wattless currents, the regulation 
of E.M.F. must be accomplished by some other method. This can be done by 
changing the ratio of the static transformer by cutting in and out turns as. 
its primary, or by the introduction of self-induction coils in the a.c. leads to 
the rotary. 

The first introduces a complicated set of connections and contacts, but is 
unlimited in range. 

The second method seems especially suited for the purpose, but is some- 
what limited in range. Theoretically the action is as follows : Suppose the 
excitation to be low enough so that the current lags 90° behind the impressed 
E.M.F. , the E.M.F. of self-induction lags 90° behind the current, and is 
therefore 180° behind the impressed E.M.F., and therefore in opposition to it. 
On the other hand, if the excitation is large, and produces a leading current 
of 90°, the E.M.F. of self-induction is in phase with the impressed E.M.F. 
and adds itself to it. Therefore, with self-induction introduced in the a.c. 
lines, it is only necessary to vary the excitation in order to change the con- 
tinuous current E.M.F. A rotary can thus be compounded by using shunt 
and series field, to maintain a constant E.M.F. under changes of load, the 
compounding taking place, of course, in the a.c. lines and not in the field of 
the machine, as usual in d.c. dynamos. 

In handling the inverted converter care must be exercised in starting it 
under load, as it is apt to run away if not connected in parallel with other 
alternators. If they are started from the d.c. side, and have lagging cur- 
rents flowing from a.c. side, this current will tend to demagnetize or weaken 
the fields, and the speed of the armature is liable to accelerate to the dan- 
ger limit. 

A lagging current taken from an inverted rotary, even after having reached 
synchronism, will cause an immediate increase in speed, and if enough lag- 
ging will cause an approach to the danger point. 

Running as a rotary, and converting from a.c. to d.c, the phase of the en- 
tering current has no effect on the speed, this being determined by the 
cycles of the driving generator, nor upon the commutation, simply influen- 
cing the heat in the armature and ratio of voltages slightly. 

Double-current generators are useful in situations where continuous cur- 
rent can be used for a portion of the day and the current transferred through 
the a.c. side to some other district for use in another portion of the day, 
thus keeping the machine under practically constant load. 

The size of double-current generators is limited by the size of the d.c. gen- 
erator that can be built with the same number of poles as a good alternator. 
The heating of the armature depends upon the sum and not the difference 
of the currents, as in the rotary, and the capacity is therefore no greater 
than a d.c. machine of the same total output. 

Automatic compounding of double current generators is scarcely feasible 
in practice, and the field must be very stable, as the demagnetizing effect of 
the lagging a.c. currents tends to drop the excitation entirely. Such machines 
run better separately excited. 



CONVERTER ARMATURE WINDINGS. 



291 



COXV£RTER -A.ROTATURE WTXB1SGS. 
Two-Circuit Winding: for Two-Phase Rotary Transformers. 

The following diagram shows the connections of the four rings to the dif- 
ferent sections of the armature. The connections are made at the commu- 
tator segments at four points, although there are six poles. 




Fig. 84. 

Two-Circuit Winding- for Three-Phase Rotary 
Transformers. 

The following diagram shows the connections of the three collector rings 
to the continuous current winding of a six-pole dynamo. As in the last fig- 
ure, the rings are connected to points on the commutator at nearly equi- 
distant points. 




Fig. 85. 



292 



MOTORS. 



Note. — Connection of Static Transformers and Rotary 
Converters. 

In the use of rotary transformers two or more of these machines are some- 
times connected in multiple to the secondary of the static transformers, and 
their direct current leads then connected in multiple to a common bus bar 
circuit, as shown in Fig. 86. 



GENERATOR 



WffiWfMQWQ 




STATIC 
TRANSFORMER 



GENERATOR 

eSEb 

hmummom 



ROTARY ROTARY 



ROTARY ROTARY 

rOi iOi 



Fig. 



Fig. 87. 



"With the above connections currents are often formed in the rotaries that 
disturb the point of commutation, and it becomes practically impossible to 
adjust the brushes so they will not spark. Rather than connect across in 
the above manner, it is better that each rotary have its own transformer, or 
at least its own secondary on the static transformer, as shown in Fig. 87. 



REPORT OP THE COMMITTEE ON 
STANDARDIZATION. 

[Adopted at the 19th Axxual Convention at Great Barrington, 
Mass., June 20, 1902.] 

Reprinted from Vol. XIX. of the Transactions. 

To the Council of The American Institute of Electrical Engineers. 

Gentlemen : Your Committee on Standardization begs to submit the 
following revised series of recommendations, which embraces the Com- 
mittee's report of 1899, amended in view of such suggestions and exten- 
sions as experience and practice have since indicated to be desirable. 

The subjects discussed in these recommendations are such as call for 
extension and revision from time to time, in view of the rapid advance 
of electrical engineering. 

Tours respectfully, 

FRANCIS B. CROCKER, Chairman, 

A. E. KENNELLY, 

JOHN W. LIEB, Jr., 

C. O. MAILLOUX, 

CHARLES P. STEINMETZ, 

LEWIS B. STILLWELL, 

ELIHU THOMSON. 

CE^ERAL PIA1T. 

Efficiency. Section* 1 to 25. 

(I) Commutating Machines, 

(II) Synchronous Machines, 

(III) Synchronous Commutating Machines, 

(IV) Rectifying Machines, 

(V) Stationary Induction Apparatus, 

(VI) Rotary Induction Apparatus, 

(VII) Transmission Lines, " 25 
Ri.«e of Temperature. Sections 26 to 35. 

Insulation. Sections 36 to 49. 

Regulation. Sections 50 to 71. 

Variation and. Pulsation. Sections 72 to 74. 

Rating-. Sections 75 to 82. 

Classification of Voltages and Frequencies. Sections 83 to 88. 

Overload Capacities. Sections 89 to 92. 

liUininous Sources. Sections 93 to 98. 

Appendices. (I) Efficiency. ♦ 

(II) Apparent Efficiency. 

(III) Power Factor and Inductance Factor. 

(IV) Notation. 

(V) Table of Sparking Distances. 
.Preliminary Definitions : 

A direct current is a unidirectional current. 

A continuous current is a steady, or non-pulsating, direct current. 

An alternating current is a current of equal half- waves in successively 
opposite directions. 

An oscillating current is a current alternating in direction, and of 
decreasing amplitude. 

Electrical Apparatus will be treated under the following heads : 

I. Commutating- machines, which comprise a constant magnetic 
field, a closed-coil armature, and a multi-segmental commutator con- 
nected thereto. 

Under this head may be classed the following : Continuous-current 
generators ; continuous- current motors ; continuous-current boosters ; 
motor-generators ; dynamotors ; converters and closed-coil arc machines. 

A booster is a machine inserted in series in a circuit to change its 
voltage, and may be driven either by an electric motor, or otherwise. In 
the former case it is a motor-booster. 

293 



Sections 7 to 10 


11 to 12 


" 13 to 16 


" 17 to 18 


" 19 to 20 


" 21 to 24 



294 DYNAMO AND MOTOR STANDARDS AND TESTING. 



A motor-generator is a transforming device consisting of two machines, 
a motor and a generator, mechanically connected together. 

A dynamotor is a transforming device combining both motor and generator 
action in one magnetic held, with two armatures, or with an armature hav- 
ing two separate windings. 

.For converters, see III. 

II. Synchronous Machines, which comprise a constant magnetic 
field, and an armature receiving or delivering alternating currents in syn- 
chronism with the motion of the machine ; i.e., having a frequency equal 
to the product of the number of pairs of poles and the speed of the machine 
in revolutions per second. 

III. Synchronous Commutating- Machines. — These include: 
1. Synchronous converters, commonly called " converters " ; i.e., converters 
from alternating to direct, or from direct to alternating current ; and 2 
Double-current generators ; i.e., generators producing both direct and 
alternating currents. 

A converter is a machine employing mechanical momentum in changing 
electric energy from one form into another. 
A converter may be either : 

a. A direct-current converter, converting from a direct current to a 
direct current, or 

b. A synchronous converter, formerly called a rotary converter, con- 
verting from an alternating to a direct current, or vice-versa. 

Phase converters are converters from an alternating-current system to 
an alternating-current system of the same frequency but in different phase. 

Frequency converters are converters from an alternating-current system 
of one frequency to an alternating-current system of another frequency, 
with or without change in the number of phases. 

IV. Rectifying' Machines, or Pulsatingr-Current Gener- 
ators, which produce a unidirectional current of periodically varying 
strength. 

V. Stationary Induction Apparatus, i.e., stationary apparatus 
changing electric energy to electric energy through the medium of magnetic 
energy. These comprise : 

a. Transformers, or stationary induction apparatus in which the pri- 
mary and secondary windings are electrically insulated from each other. 

b. Auto-transformers, also called compensators ; i.e., stationary induc- 
tion apparatus, in which part of the primary winding is used as a secondary 
winding ; or conversely. 

c. Potential regulators, or stationary induction apparatus having a coil 
in shunt, and a coil in series with the circuit, so arranged that the ratio of 
transformation between them is variable at will. 

These may be divided into the following types, or combinations thereof : 

1. Compensator potential-regulators, in which the number of turns of 
one of the coils is changed. 

3. Induction potential-regulators, in which the relative positions of pri- 
mary and secondary coils is changed. 

3. Magneto potential-regulators, in which only the direction of the mag- 
netic flux with respect to the coils is changed. 

d. Reactors, or Reactance coils, formerly called choking coils ; i.e., sta- 
tionary induction apparatus used to produce impedance or phase displace- 
ment. 

VI. Rotary Induction Apparatus, which consist of primary and 
secondary windings rotating with respect to each other. They comprise : 

a. Induction motors. 

b. Induction generators. 

c. Frequency converters. 

d. Rotary phase converters. 

EFFICIENCY. 

1. The " efficiency" of an apparatus is the ratio of its net power output 
to its gross power input.* 

* An exception should be noted in the case of storage batteries or apparatus for 
storing energy in which the efficiency, unless otherwise qualified, should be under- 
stood at the ratio of the energy output to the energy intake in a normal cycle. 



REPORT OF COMMITTEE ON STANDARDIZATION. 295 

H. The efficiency of all apparatus, except such as may be intended for 
intermittent service, should be either measured at, or reduced to, the tem- 
perature which the apparatus assumes under continuous operation at full 
rated load, referred to a room temperature of 25 ° G. 

With apparatus intended for intermittent service, the efficiency should be 
determined at the temperature assumed under specified conditions. 

3. Electric power should be measured at the terminals of the apparatus. 

•4. In determining the efficiency of alternating-current apparatus, the 
electric power should be measured when the current is in phase with the 
E.M.F., unless otherwise specified, except when a definite phase difference 
is inherent in the apparatus, as in induction motors, induction generators, 
frequency converters, etc. 

5. Mechanical power in machines should be measured at the pulley, 
gearing, coupling, etc., thus excluding the loss of power in said pulley, 
gearing, or coupling, but including the bearing friction and windage. The 
magnitude of bearing friction and windage may be considered as indepen- 
dent of the load. The loss of power in the belt and the increase of bearing 
friction due to belt tension, should be excluded. Where, however, a ma- 
chine is mounted upon the shaft of a prime mover, in such a manner that 
it cannot be separated therefrom, the frictional losses in bearings and in 
windage, which ought, by definition, to be included in determining the 
efficiency, should be excluded, owing to the practical impossibility of deter- 
mining them satisfactorily. The brush friction, however, should be in- 
cluded. 

Where a machine has auxiliary apparatus, such as an exciter, the power 
lost in the auxiliary apparatus should not be charged to the machine but 
to the plant consisting of machine and auxiliary apparatus taken together. 
The plant efficiency in such cases should be distinguished from the machine 
efficiency. 

O. The efficiency may be determined by measuring all the losses individ- 
ually, and adding their sum to the output to derive the input, or subtract- 
ing their sum from the input to derive the output. All losses should be 
measured at, or reduced to, the temperature assumed in continuous opera- 
tion, or in operation under conditions specified. ( See Sections 26 to 35. ) 

In order to consider the application of the foregoing rules to various 
machines in general use, the latter may be conveniently divided into classes 
as follows : 

I. Commutating- Machines. 



H. In commutating machines the 

a. Bearing friction and windage. ( See Section 5.) 

b. Molecular magnetic friction, and eddy currents in iron and copper, 
also I 2 r losses in cross-connections of cross-connected armatures. These 
losses should be determined with the machine on open circuit, and at a 
voltage equal to the rated voltage + lr in a generator, and — Ir in a mo- 
tor, where / denotes the current strength and r denotes the internal 
resistance of the machine. They should be measured at the correct speed 
and voltage, since they do not usually vary in any definite proportion to the 
speed or to the voltage. 

c. Armature resistance losses. I 2 r', where lis the current strength in 
the armature, and r' is the resistance between armature brushes, excluding 
the resistance of brushes and brush contacts. 

d. Commutator brush friction. 

e. Commutator brush-contact resistance. It is desirable to point out that 
with carbon brushes the losses (d) and (e) are usually considerable in low- 
voltage machines. 

/. Field excitation. With separately excited fields, the loss of power in 
the resistance of the field coils alone should be considered. With shunt 
fields or series fields, however, the loss of power in the accompanying rheo- 
stat should also be included, the said rheostat being considered as an essen- 
tial part of the machine, and not as separate auxiliary apparatus. 

(b) and (c) are losses in the armature or " armature losses " ; (d) and (e) 
" commutator losses" ; (/) " field losses." 

8. The difference between the total losses under load and the sum of the 
losses above specified, should be considered as " load losses," and are usu- 
ally trivial in commutating machines of small field distortion. When the 



296 DYNAMO AND MOTOR STANDARDS AND TESTING. 

field distortion is large, as is shown by the necessity for shifting the brushes 
between no load and full load, or with variations of load, these load losses 
may be considerable, and should be taken into account. This applies es- 
pecially to constant-current arc-light generators. In this case the efficiency 
may be determined either by input and output measurements, or the load 
losses may be estimated by the method of Section II. 

O. Boosters should be considered and treated like other direct-current 
machines in regard to losses. 

ie>. In motor-generators, dynamotors, or converters, the efficiency is the 
electric output divided by the electric input. 

II. Synchronous Machines. 

11. In synchronous machines the output or input should be measured 
with the current in phase with the terminal E.M.F., except when otherwise 
expressly specified. 

13. The losses in synchronous machines are : 

a. Bearing friction and windage. (See Section 5.) 

b. Molecular magnetic friction, and eddy currents in iron, copper, and 
other metallic parts. These losses should be determined at open circuit of 
the machine at the rated speed and at the rated voltage, + 1 r in a synchro- 
nous generator, — Ir in a synchronous motor, where 1 = current in arma- 
ture, r = armature resistance. It is undesirable to compute these losses 
from observations made at other speeds or voltages. 

These losses may be determined either by driving the machine by a motor, 
or by running it as a synchronous motor, and adjusting its fields so as to get 
minimum current input, and measuring the input by wattmeter. 

In the latter case, with polyphase machines, several wattmeters must be 
used, arranged so as to measure unbalanced load. The former method is 
preferable, since the latter is liable to error caused by acceleration and 
retardation due to a pulsation of frequency or an inherent tendency to 
surging. 

c. Armature-resistance loss, which maybe expressed bypl 2 r; where r 
= resistance of one armature circuit or branch, 1 = the" current in such 
armature circuit or branch, and j) = the number of armature circuits or 
branches. 

d. Eoad losses as defined in Section 8. While these losses cannot well 
be determined individually, they may be considerable, and, therefore, their 
joint influence should be determined by observation. This can be done by 
operating the machine on short circuit and at full-load current ; that is, by 
determining what may be called the " short-circuit core loss." With the 
low field intensity and great lag of current existing in this case, the load 
losses are usually greatly exaggerated. 

One-third of the short-circuit core loss may, as an approximation, and in 
the absence of more accurate information, be assumed as the load loss. 

e. Collector-ring friction and contact resistance. These are generally 
negligible, except in machines of extremely low voltage. 

/. Field excitation. In separately-excited machines, the I 2 r of the field 
coils proper should be used. In self-exciting machines, however, the loss in 
the field rheostat should be included. (See Section If.) 

III. Synchronous Conimutating- Machines. 

13. In converters, the power on the alternating-current side is to be 
measured with the current in phase with the terminal E.M.F., unless other- 
wise specified. 

1-4. In double-current generators, the efficiency of the machine should 
be determined as a direct-current generator in accordance with Section 7, 
and as an alternating-current generator in accordance with Section 12. 
The two values of efficiency may be different, and should be clearly dis- 
tinguished. 

15». In converters the losses should be determined when driving the ma- 
chine by a motor. These losses are : 

a. Bearing friction and windage. (See Section 5.) 

b. Molecular magnetic friction, and eddy currents in iron, copper, and 
metallic parts ; also, I' 2 r loss, due to cross-current in cross-connected 



REPORT OF COMMITTEE ON STANDARDIZATION. 297 



armatures. These losses should be determined at open circuit and at the 
rated terminal voltage, no allowance being made for the armature resist- 
ance, since the alternating and the direct currents flow in opposite direc- 
tions. 

c. Armature resistance. The loss in the armature is q I 2 r, where 1 = 
direct current in armature, r = armature resistance, and q, a factor which 
is equal to 1.47 in single-circuit single-phase, 1.15 in double-circuit single- 
phase, 0.59 in three-phase, 0.39 in quarter-phase, and 0.27 in six-phase con- 
verters. 

d. Load losses. The load losses should be determined in the same 
manner as described in Section 12 d, with reference to the direct-current 
side. 

e and/. Losses in commutator and collector friction and brush contact 
resistance. (See Sections 7 and 12.) 

g. Field excitation. In separately-excited fields, the I 2 r loss in the field 
coils proper should be taken, while in shunt and series fields the rheostat 
loss should be included, except where fields and rheostats are intentionally 
modified to produce effects outside of the conversion of electric power, as 
for producing phase displacement for voltage control. In this case 25 per 
cent of the I' 2 r loss in the field proper at non-inductive alternating circuit 
should be added as proper estimated allowance for normal rheostat losses. 
(See Section If.) 

1G. Where two similar synchronous machines are available, their effi- 
ciency can be determined by operating one machine as a converter from 
direct to alternating, and the other as a converter from alternating to 
direct, connecting the alternating sides together, and measuring the differ- 
ence between the direct-current input and the direct-current output. This 
process may be modified by returning the output of the second machine 
through two boosters into the first machine and measuring the losses. An- 
other modification is to supply the losses by an alternator between the two 
machines, using potential regulators. 

IV. Rectifying- machines, or Pulsating-Current Gener- 
ators. 

17. These include : Open-coil arc machines, constant-current rectifiers, 
constant-potential rectifiers. 

The losses in open-coil arc machines are essentially the same as in Sec- 
tions 7 to 10 (closed-coil commutating machines). In this case, however, 
the load losses are usually greater, and the efficiency should be measured 
by input-and-output test, using wattmeters for measuring the output. In 
alternating-current rectifiers, the output must be also measured by watt- 
meter, and not by voltmeter and ammeter ; since owing to the pulsation of 
current and E.M.F., a considerable discrepancy may exist between watts 
and volt-amperes, amounting to as much as 10 or 15 per cent. 

IS. In constant-current rectifiers, transforming from constant-potential 
alternating to constant direct current by means of constant-current trans- 
forming devices and rectifying commutators, the losses in the transformers 
are to be included in the efficiency, and have to be measured when operat- 
ing the rectifier, since in this case the losses are generally greater than 
when feeding an alternating secondary circuit. In constant-current trans- 
forming devices, the load losses may be considerable, and, therefore, should 
not be neglected. 

The most satisfactory method of determining the efficiency in rectifiers is 
to measure electric input and electric output by wattmeter. The input is 
usually inductive, owing to a considerable phase displacement, and to wave 
distortion. For this reason the apparent efficiency should also be consid- 
ered, since it is usually much lower than the true efficiency. The power 
consumed by the synchronous motor or other source driving the rectifier 
should be included in the electric input. 

V. Stationary Induction Apparatus. 

lf>. Since the efficiency of induction apparatus depends upon the wave 
shape of E.M.F., it should be referred to a sine Avave of E.M.F., except 
where expressly specified otherwise. The efficiency should be measured 



298 DYNAMO AND MOTOR STANDARDS AND TESTING. 



with non-inductive load, and at rated frequency, except where expressly 
specified otherwise. The losses are : 

a. Molecular magnetic friction and eddy currents measured at open cir- 
cuit and at rated voltage — Ir, where /rr rated current, r= resistance of 
primary circuit. 

b. Resistance losses, the sum of the l 2 r in the primary and in the sec- 
ondary windings of a transformer, or in the two sections of the coil in a 
compensator or auto- transformer, where I recurrent in the coil or section 
of coil. r = resistance. 

c. Load losses, i.e., eddy currents in the iron, and especially in the copper 
conductors, caused by the current. They should he measured by short-circuit- 
ing the secondary of the transformer and impressing upon the primary an 
E.M.F. sufficient to send full-load current through the transformer. The 
loss in the transformer under these conditions measured by wattmeter gives 
the load losses-p-i 2 r losses in both primary and secondary coils. 

d. Losses due to the methods of cooling, as power consumed by the blower 
in air-blast transformers, and power consumed by the motor driving pumps 
in oil or water-cooled transformers. Where the same cooling apparatus 
supplies a number of transformers or is installed to supply future additions, 
allowance should be made therefor. 

2©. In potential regulators, the efficiency should be taken at the maxi- 
mum voltage for which the apparatus is designed, and with non-inductive 
load, unless otherwise specified. 

VI. Rotary Induction Apparatus. 

21. Owing to the existence of load losses, and since the magnetic density 
in the induction motor under load changes in a complex manner, the effi- 
ciency should be determined by measuring the electric input by wattmeter, 
and the mechanical output at the pulley, gear, coupling, etc. 

22. The efficiency should be determined at the rated frequency, and the 
input measured with sine waves of impressed E.M.F. 

23. The efficiency may be calculated from the apparent input, the power 
factor, and the power output. The same applies to induction generators. 
Since phase displacement is inherent in induction machines, their apparent 
efficiency is also important. 

24. In frequency converters, i.e., apparatus transforming from an alter- 
nating system to an alternating system of different frequency, with or 
without a change in the number of phases, and in phase converters, i.e., 
apparatus converting from an alternating system, usually single-phase, to 
another alternating system, usually polyphase, of the same frequency, the 
efficiency should also be determined by "measuring both output and input, 

VII. Transmission lines. 

25». The efficiency of transmission lines should be measured with non- 
inductive load at the receiving end, with the rated receiving pressure and 
frequency, also with sinusoidal impressed E.M.F.'s, except where expressly 
specified otherwise, and Avith the exclusion of transformers or other appa- 
ratus at the ends of the line. 

RISE OF lEMPEHATrHE. 
General Principles. 

2G. Under regular service conditions, the temperature of electrical 
machinery should never be allowed to remain at a point at which perma- 
nent deterioration of its insulating material takes place. 

'27. The rise of temperature should be referred to the standard condi- 
tions of a room-temperature of 25° C, a barometric pressure of 760 mm. and 
normal conditions of ventilation ; that is, the apparatus under test should 
neither be exposed to draught nor inclosed, except where expressly 
specified. 

28. If the room-temperature during the test differs from 25° C, the 
observed rise of temperature should be corrected by £ per cent for each 
degree C. Thus with a room-temperature of 35° C, the observed rise of 



REPORT OF COMMITTEE ON STANDARDIZATION. 299 



temperature lias to be decreased by 5 per cent, and with a'room-temperature 
of 15° C the observed rise of temperature has to be increased by 5 per cent. 
The thermometer indicating the room-temperature should be screened from 
thermal radiation emitted by heated bodies, or from draughts of air. When 
it is impracticable to secure normal conditions of ventilation on account of 
an adjacent engine, or other sources of heat, the thermometer for measuring 
the air temperature should be placed so as fairly to indicate the temperature 
which the machine would have if it were idle, in order that the rise of 
temperature determined shall be that caused by the operation of the 
machine. 

SO. The temperature should be measured after a run of sufficient dura- 
tion to reach practical constancy. This is usually from 6 to 18 hours, ac- 
cording to the size and construction of the apparatus. It is permissible, 
however, to shorten the time of the test by running a lesser time on an 
overload in current and voltage, then reducing the load to normal, and 
maintaining it thus until the temperature has become constant. 

In apparatus intended for intermittent service, as railway motors, start- 
ing rheostats, etc., the rise of temperature should be measured after opera- 
tion under as nearly as possible the conditions of service for which the 
apparatus is intended, and the conditions of the test should be specified. 

In apparatus which by the nature of their service may be exposed to over- 
load, as railway converters, and in very high voltage circuits, a smaller rise 
of temperature should be specified than in apparatus not liable to overloads 
or in low voltage apparatus. In apparatus built for conditions of limited 
space, as railway motors, a higher rise of temperature must be allowed. 

3©. In electrical conductors, the rise of temperature should be deter- 
mined by their increase of resistance, where practicable. For this purpose 
the resistance may be measured either by galvanometer test, or by drop-of- 
potential method. A temperature coefficient of 0.42 per cent per degree C, 
from and at 0° C, may be assumed for copper.* Temperature elevations 
measured in this way are usually in excess of temperature elevations 
measured by thermometers. 

When thermometers are applied to the free surface of a machine, it is 
desirable that the bulb of the thermometer should be covered by a pad of 
definite area. A convenient pad may be formed of cotton waste in a shallow 
circular box about one and a half inches in diameter, through a slot in the 
side of which the thermometer bulb is inserted. An unduly large pad over 
the thermometer tends to interfere with the natural liberation of heat from 
the surface to which the thermometer is applied. 

31. With apparatus in which the insulating materials have special heat- 
resisting qualities a higher temperature elevation is permissible. 

33. In apparatus intended for service, in places of abnormally high 
temperature, a lower temperature elevation should be specified. 

33. It is recommended that the following maximum values of tempera- 
ture elevation should not be exceeded : 
Commutating machines, rectifying machines, and synchronous machines : 
Field and armature, by resistance, 50° C. 
Commutator and collector rings and brushes, by thermometer, 

55° C. 
Bearings and other parts of machine, by thermometer, 40° C. 
Rotary induction apparatus : 

Electric circuits, 50° C, by resistance. 

Bearings and other parts of the machine, 40° C, by thermometer. 
In squirrel-cage or short-circuited armatures, 55° C, by thermometer, 
may be allowed. 
Transformers for continuous service — electric circuits by resistance, 

* By the formula 

l?t=B (1 + 0.0042 t) and lit + 6 —. B [1 -f 0.0042 (* -f 9) 
where Rt is the initial resistance at room-temperature t° C. 

Rt-\-9 is the final resistance at temperature elevation 0° C. 
R Q is the inferred resistance at 0° C. 
These combine into the formula 

e = (238.1 + ( ^^ - 1 ) degrees C. 



300 DYNAMO AND MOTOR STANDARDS AND TESTING. 



50° C, other parts by thermometer, 40° (?., under conditions of normal 
ventilation. 

Reactors, induction- and magneto-regulators — electric circuits by re- 
sistance, 50° C, other parts by thermometer, 40° C. 

Where a thermometer, applied to a coil or winding, indicates a higher 
temperature elevation than that shown by resistance measurement, the 
thermometer indication should be accepted. In using tbe thermometer, 
care should be taken so to protect its bulb as to prevent radiation from it, 
and, at the same time, not to interfere seriously with the normal radiation 
from the part to which it is applied. 

34. In the case of apparatus intended for intermittent service, except 
railway motors, the temperature elevation which is attained at the end 
of the period corresponding to the term of full load, should not exceed 
50° C, by resistance in electric circuits. In the case of transformers 
intended for intermittent service, or not operating continuously at full 
load, but continuously in circuit, as in the ordinary case of lighting trans- 
formers, the temperature elevation above the surrounding air-temperature 
should not exceed 50° C. by resistance in electric circuits and 40° C. by 
thermometer in other parts, after the period corresponding to the term 
of full load. In this instance, the test load should not be applied until 
the transformer has been in circuit for a sufficient time to attain the tem- 
perature elevation due to core loss. With transformers for commercial 
lighting, the duration of the full-load test may be taken as three hours, 
unless otherwise specified. In the case of railway, crane, and elevator 
motors, the conditions of service are necessarily so varied that no specific 
period corresponding to the full-load term can be stated. 

35. The commercial rating of a railway motor should be the h. p. out- 
put giving 75° C. rise of temperature, above a room temperature of 25° C. 
after one hour's continuous run at 500 volts terminal pressure, on a stand, 
with the motor covers removed. 

For determining the service temperature of a railway motor, the tem- 
perature rise should be determined by operating the motor on a straight 
and level track and under specified conditions : — 

(1).. As to the load carried in tons per motor. 

(2). The schedule speed in miles per hour. 

(3). The number of stops per mile. 

(4). The duration in seconds of the stops. 

(5). The acceleration to be developed in miles per hour per second. 

(6). The braking retardation to be developed in miles per hour per second. 

These specifications should be determined, or agreed upon, as equivalent 
to the actual service, and the motors to be closed or open, according to the 
way in Avhich they are to be operated in service. 

The tests should be made in both directions over the same track. 

By a "level track " should be understood a track in which the gradient 
does not exceed one-half per cent at any point. 

By a "straight track" should be understood a track in which the radius 
of curvature is nowhere less than the distance traveled by the car in 
30 seconds, at the maximum speed reached during the run. 

The wind velocity during a test should not exceed 10 miles per hour in 
any direction. 

OiLLATIOlS. 

30. The ohmic resistance of the insulation is of secondary importance 
only, as compared with the dielectric strength, or resistance to rupture by 
high voltage. 

Since the ohmic resistance of the insulation can be very greatly in- 
creased by baking, but the dielectric strength is liable to be weakened 
thereby, it is preferable to specify a high dielectric strength rather than a 
high insulation resistance. The high-voltage test for dielectric strength 
should always be applied. 

Insulation Resistance. 

3*. Insulation resistance tests should, if possible, be made at the pres- 
sure for which the apparatus is designed. 
The insulation resistance of the complete apparatus must be such that 



REPORT OF COMMITTEE ON STANDARDIZATION. 301 



the rated voltage of the apparatus will not send more than of 

j ,uuu,ouu 
the full-load current, at the rated terminal voltage, through the insula- 
tion. Where the value found in this way exceeds 1 megohm, 1 megohm is 
sufficient. 

Dielectric Streng-tli. 

38. The dielectic strength or resistance to rupture should he deter- 
mined by a continued application of an alternating E.M.F. for one minute. 
The source of alternating E.M.F. should be a transformer of such size that 
the charging current of the apparatus as a condenser does not exceed 25 
per cent of the rated output of the transformer. 

30. In alternating-current apparatus, the test should be made at the 
frequency for which the apparatus is designed. 

40. The high-voltage tests should not be applied when the insulation is 
low, owing to dirt or moisture, and should be applied before the machine 
is put into commercial service. 

The high potential test should be made at the temperature consumed 
under normal operation, as specified in Paragraph 2 under "Efficiency." 

41. It should be pointed out that tests at high voltages considerably in 
excess of the normal voltages, to determine whether specifications are 
fulfilled, are admissible on new machines only. 

43. The test for dielectric strength should be made with the completely 
assembled apparatus and not with its individual parts, and the voltage 
should be applied as follows * : — 

1st. Between electric circuits and surrounding conducting material, and 

2d. Between adjacent electric circuits, where such exist, as in trans- 
formers. 

The tests should be made with a sine wave of E.M.F., or where this is 
not available, at a voltage giving the same striking distance between 
needle points in air, as a sine wave of the specified E.M.F., except where 
expressly specified otherwise. As needles, new sewing-needles should be 
used. It is recommended to shunt the apparatus during the test by spark 
gap of needle points set for a voltage exceeding the required voltage 
by 10 per cent. 

A table of approximate sparking distances is given in Appendix V. 

43. The following voltages are recommended for apparatus not includ- 
ing transmission lines or switchboards : — 

Rated Terminal Voltage. Rated Output. Testing Voltage. 

Not exceeding 400 volts .... Under 10 k. w. . 1,000 volts. 

" " " " 10 k. w. and over 1,500 " 

400 and over, but less than 800 volts. Under 10 k. w. . 1,500 " 

" " " " 10k. w. and over 2,000 " 

800 " " 1,200 " Any 3,500 " 

1,200 " " 2,500 " Any ..... 5,000 " 

(Double the nor- 

2,500 " " 10,000 " Any J mal rated 

( voltages. 
( 10,000 volts 

10,000 " " 20,000 " Any ] above normal 

( rated voltages. 
( 50 per cent above 

20,000 " .... Any I normal rated 

( voltages. 
Except that transformers of 5,000 volts or less, directly feeding con- 
sumption circuits, should be tested at 10,000 volts. 
Synchronous motor fields and fields of converters started 
from the alternating current side 5,000 volts. 

Alternator field circuits should be tested under a breakdown test voltage 
corresponding to the rated voltage of the exciter, and referred to an out- 

* Note.— This Section (No. 42) was referred hack by the Convention to the. 
Committee with power to amend, and may be subsequently revised. — Editok. 



302 DYNAMO AND MOTOR STANDARDS AND TESTING. 



put equal* to the output of the alternator ; i.e., the exciter should he rated 
for this test as having an output equal to that of the machine it excites. 

Condensers should be tested at twice their rated voltage and at their 
rated frequency. 

The values in the table above are effective values, or square roots of 
mean square, reduced to a sine wave of E.M.F. 

44. In testing insulation between different electric circuits, as between 
primary and secondary of transformers, the testing voltage must be chosen 
corresponding to the high-voltage circuit. 

45. In transformers of 20,000 volts upwards, it should be sufficient to 
test the transformer by operating it at 50 per cent above its rated voltage ; 
if necessary, with sufficiently higher frequency to induce this voltage. 

40. The test of the insulation of a transformer, if no testing transformer 
is available, may be made by connecting one terminal of the high-voltage 
winding to the core and low-voltage winding, and then repeating the test 
with the other terminal of the high-voltage winding so connected. The 
test of dielectric resistance between the low-voltage winding and the core 
should be in accordance with the recommendation in Section 43, for sim- 
ilar voltages and capacities. 

4*. High-voltage tests on transformers or other apparatus should be 
based upon the voltages between the conductors of the circuit to which 
they are connected. 

48. When machines or apparatus are to be operated in series, so as to 
employ the sum of their separate E.M.F. 's, the voltage should be referred 
to this sum, except where the frames of the machines are separately in- 
sulated both from ground and from each other. 

The insulation between machines and between each machine and ground 
should be tested, the former referred to the voltage of one machine, and 
the latter to the total voltage of the series. 

49. Underground cables, and line switches, should be tested by the 
application of an alternating E.M.F. for one minute at twice the voltage 
at which the cable or switch is to be operated. 

REGULATION. 

5©. The term "regulation" should have the same meaning as the term 
" inherent regulation," at present frequently used. 

51. The regulation of an apparatus intended for the generation of con- 
stant potential, constant current, constant speed, etc., is to be measured 
by the maximum variation of potential, current, speed, etc., occurring 
within the range from full-load to no-load, under such constant conditions 
of operation as give the required full-load values, the condition of full-load 
being considered in all cases as the normal condition of operation. 

5*3. The regulation of an apparatus intended for the generation of a 
potential, current, speed, etc., varying in a definite manner between full- 
load and no-load, is to be measured by the maximum variation of 
potential, current, speed, etc., from the satisfied condition, under such con- 
stant conditions of operation as give the required full-load values. 

If the manner in which the variation in potential, current, speed, etc., 
between full-load and no-load, is not specified, it should be assumed to be 
a simple linear relation ; i.e., undergoing uniform variation between full- 
load and no-load. 

The regulation of an apparatus may, therefore, differ according to its 
qualification for use. Thus, the regulation of a compound-wound gener- 
ator specified as a constant-potential generator, will be different from 
that it possesses when specified as an over-compounded generator. 

53. The regulation is given in percentage of the full-load value of 
potential, current, speed, etc., and the apparatus should be steadily 
operated during the test under the same conditions as at full-load. 

54. The regulation of generators is to be determined at constant speed, 
of alternating apparatus at constant impressed frequency. 

55. The regulation of a generator-unit, consisting of a generator united 
with a prime-mover, should be determined at constant conditions of the 
prime mover; i.e., constant steam pressure, head, etc. It would include 
the inherent speed variations of the prime-mover. For this reason the 
regulation of a generator-unit is to be distinguished from the regulation of 



REPORT OF COMMITTEE ON STANDARDIZATION. 303 



either the prime-mover, or of the generator contained in it, when taken 
separately. 

5»fi. In apparatus generating, transforming or transmitting alternating 
currents, regulation should be understood to refer to non-inductive load ; 
that is, to a load in which the current is in phase with the E.M.F. at the 
output side of the apparatus, except where expressly specified otherwise. 

5*. In alternating apparatus receiving electric power, regulation should 
refer to a sine wave of E.M.F., except where expressly specified otherwise. 

58. In commutating machines, rectifying machines, and synchronous 
machines, as direct-current generators and motors, alternating-current 
and polyphase generators, the regulation is to be determined under the 
following conditions : 

a. At constant excitation in separately excited fields ; 

b. With constant resistance in shunt-field circuits ; and 

c. With constant resistance shunting series fields ; i.e., the field ad- 
justment should remain constant, and should be so chosen as to give the 
required full-load voltage at full-load current. 

50. In constant-potential machines, the regulation is the ratio of the 
maximum difference of terminal voltage from the rated full-load value 
(occurring within the range from full load to open circuit) to the full-load 
terminal voltage. 

GO. In constant-current apparatus, the regulation is the ratio of the 
maximum difference of current from the rated full-load value (occurring 
within the range from full-load to short-circuit, or minimum limit of 
operation) to the full-load current at constant speed ; or, in transformers, 
etc., at constant impressed voltage and frequency. 

©1. In constant-power apparatus, the regulation is the ratio of maxi- 
mum difference of power from the rated full-load value ('occurring within 
the range of operation specified) to the rated power. 

©3. In over-compounded machines, the regulation is the ratio of the 
maximum difference in voltage from a straight line connecting the no-load 
and full-load values of terminal voltage as function of the current, to the 
full-load terminal voltage. 

©3. In constant-speed continuous-current motors, the regulation is the 
ratio of the maximum variation of speed from its full-load value (occurring 
within the range from full-load to no-load) to the full-load speed. 

©4. In constant-potential non-inductive transformers, the regulation is 
the ratio of the rise of secondary terminal voltage from full-load to no-load 
(at constant primary impressed terminal voltage) to the secondary terminal 
voltage. 

©5. In induction motors, the regulation is the ratio of the rise of speed 
from full-load to no-load (at constant impressed voltage) to the full-load 
speed. 

The regulation of an induction motor is, therefore, not identical with the 
slip of the motor, which is the ratio of the drop in speed from synchronism, 
to the synchronous speed. 

©©. In converters, dynamotors, motor-generators, and frequency-conver- 
ters, the regulation is the ratio of the maximum difference of terminal 
voltage at the output side from the rated full-load voltage (at constant im- 
pressed voltage and at constant frequency) , to the full-load voltage on the 
output side. 

©?. In transmission lines, feeders, etc., the regulation is the ratio of 
maximum voltage difference at the receiving-end, between no-load and full 
non-inductive load, to the full-load voltage at the receiving-end, with con- 
stant voltage impressed upon the sending end. 

©8. In steam engines, the regulation is the ratio of the maximum varia- 
tion of speed in passing from full-load to no-load (at constant steam pres- 
sure at the throttle) to the full-load speed. 

©O. In a turbine or other water-motor, the regulation is the ratio of the 
maximum variation of speed from full-load to no-load (at constant head of 
water ; i.e., at constant difference of level between tail race and head race), 
to the full-load speed. 

^O. In alternating-current apparatus, in addition to the non-inductive 
regulation, the impedance ratio of the apparatus should be specified ; i.e., 
the ratio of the voltage consumed by the total internal impedance of the 
apparatus at full-load current, to its rated full-load voltage. As far as 
possible, a sinusoidal current should be used. 



304 DYNAMO AND MOTOR STANDARDS AND TESTING. 



*1. When in synchronous machines the regulation is computed from the 
terminal voltage and impedance voltage, the exciting ampere-turns corre- 
sponding to terminal voltage plus armature-resistance-drop, and the ampere 
turns at short-circuit corresponding to the armature-impedance-drop, 
should be combined vectorially to obtain the resultant ampere-turns, and 
the corresponding internal E.M.F. should be taken from the saturation 
curve. * 

Variation and .Pulsation. 

S3. In prime movers which do not give an absolutely uniform rate of 
rotation or speed, as in steam-engines, the "variation" is the maximum 
angular displacement in position of the revolving member expressed in de- 
grees, from the position it would occupy with uniform rotation, and with 
one revolution as 360° ; and the pulsation is the ratio of the maximum 
change of speed in an engine cycle to the average speed. 

tli. In alternators or alternating-current circuits in general, the variation 
is the maximum difference in phase of the general wave of E.M.F. from a 
wave of absolutely constant frequency, expressed in degrees, and is due to 
the variation of the prime-mover. The pulsation is the ratio of the maxi- 
mum change of frequency during an engine cycle to the average frequency. 

9 ■*. If ?i = number of poles, the variations of an alternator is n / 2 times 
the variation of its prime-mover if direct connected, and n/2p times the 
variation of the prime-mover if rigidly connected thereto in the velocity 
ratio p. 

RATIJfG. 

VS. Both electrical and mechanical power should be expressed in kilo- 
watts, except when otherwise specified. Alternating-current apparatus 
should be rated in kilowatts on the basis of non-inductive condition; i.e., 
with the current in phase with the terminal voltage. 

'SO. Thus, the electric power generated by an alternating-current appa- 
ratus equals its rating only at non-inductive load; that is, when the current 
is in phase with the terminal voltage. 

t7. Apparent power should be expressed in kilovolt-amperes as distin- 
guished from real power in kilowatts. 

S8. If a power-factor other than 100 per cent is specified, the rating 
should be expressed in kilovolt amperes, and poweivfactor, at full-load. 

•JO The full-load current of an electric generator is that current which 
with the rated full-load terminal voltage gives the rated kilowatts, but in 
alternating-current apparatus only at non-inductive load. 

80. Thus, in machines in which the full-load voltage differs from the no- 
load voltage, the full-load current should refer to the former. 

If P = rating of an electric generator and E = full-load terminal voltage, 
the full-load current is : 
p 
i"=— in a continuous-current machine or single-phase alternator. 

p 

I=z — in a three-phase alternator. 

E^3 
p 
/=:—-=, in a quarter-phase alternator. 

2i Mi 

81. Constant-current machines, such as series arc-light generators, should 
be rated in kilowatts based on terminal volts and amperes at full-load. 

82. The rating of a fuse or circuit-breaker should be the current strength 
which it will continually carry. In addition thereto, the current strength 
at which it will open the circuit should be specified. 

Classification of Voltag-es and Frequencies. 

83. In direct-current, low-voltage generators, the following average ter- 
minal voltages are in general use and are recommended : 

125 volts. 250 volts. 550 to 600 volts. 

* Note. — This Section (No. 71) was referred back by tlie Convention to tlie Com- 
mittee with power to amend, and may be subsequently revised. 



REPORT OE COMMITTEE ON STANDARDIZATION. 305 



S4-. Indirect-current and alternating-current low-voltage circuits, thefol- 
lowing average terminal voltages are in general use and are recommended : 
110 volts 220 volts. 

In direct-current power circuits, for railway and other service, 500 volts 
may be considered as standard. 

Si>. In alternating-current, constant-potential, primary-distribution cir- 
cuits, an average E.M.F. of 2,200 volts, with step-down transformers of 
ratios 1/10 and 1 /20, is in general use, and is recommended. 

SO. In alternating-current, constant-potential, high-pressure circuits, at 
the receiving end, the following voltages are in general use and are recom- 
mended : 

6,000, 10,000. 15,000. 20,000. 30,000. 40,000. 60,000. 

S*. In alternating-current generators, or generating systems, a range of 
terminal voltage should be provided from no-load voltage to 10 per cent in 
excess thereof, to cover drop in transmission. If a greater range than ten 
per cent is specified, the generator should be considered as special. 

SS. In alternating-current circuits, the following approximate frequen- 
cies are recommended as desirable : 

25 ~~ 60 -«w 120 ~**.* 

These frequencies are already in extensive use, and it is deemed advisable 
to adbere to them as closely as possible. 

Overload Capacities. 

S©. All guarantees on heating, regulation, sparking, etc., should apply 
to the rated load, except where expressly specified otherwise, and in alter- 
nating-current apparatus to the current in phase with the terminal E.M.F., 
except Avhere a phase displacement is inherent in the apparatus. 

90. All apparatus should be able to carry the overload specified in Sec- 
tion 92, without self-destruction by heating, sparking, mechanical weakness, 
etc., and with an increase in temperature elevation not exceeding 15° C., 
above those specified for full loads, the overload being applied after the 
apparatus has acquired the temperature corresponding to full-load continu- 
ous operation. (See Sections 30 to 34.) 

©1. Overload guarantees should refer to normal conditions of operation 
regarding speed, frequency, voltage, etc., and to non-inductive conditions 
in alternating apparatus, except where a phase displacement is inherent in 
the apparatus. 

©2. The following overload capacities are recommended : 

1st. In direct-current generators and alternating-current generators, 
25 per cent for two hours. 

2d. In direct-current motors, induction motors, and synchronous motors, 
not including railway motors and other apparatus intended for intermittent 
service, 25 per cent for two hours, and 50 per cent for one minute, for 
momentary overload capacity. 

3d. Synchronous converters, 50 per cent for one-half hour. 

4th. Transformers, 25 per cent for two hours. Except in transformers 
connected to apparatus for which a different overload is guaranteed, in 
which case the same guarantees shall apply for the transformers as for the 
apparatus connected thereto 

5th. Exciters of alternators and other synchronous machines, 10 per cent 
more overload than is required for the excitation of the synchronous 
machine at its guaranteed overload, and for the same period of time. 

6th. All exciters of alternating-current, single-phase or polyphase gen- 
erators should be able to give, at constant speed, sufficient voltage to excite 
the alternator, at the rated speed, to the full-load terminal voltage, at the 
rated output in kilovolt-amperes and with 50 per cent power factor. 

Luminous Sources. 

©3. It is customary in industrial practice at the present time to rate 
incandescent lamps upon the basis of their mean horizontal candle-power; 
but in comparing sources of light in which the relative distribution of 

* The frequency of 12(V^ may be considered as covering the already exist- 
ing commercial frequencies between 120~w and 140^. 



305a DYNAMO AND MOTOR STANDARDS AND TESTING. 



luminosity differs considerably, the comparison should be based upon the 
total quantity of light, or total flux of light emitted by each source. 

OJ-. The mean spherical intensity of a luminous source is its total flux 
of light, expressed in lumens, divided by 4tt. If the mean spherical inten- 
sity be expressed in British candles, the flux of light will be in British- 
candle lumens (B. C. Lumens). If the mean spherical intensity be expressed 
in Hefners, the flux of light will be expressed in Hefner lumens (H. 
Lumens). 

OS. The efficiency of a luminous source should be defined as the ratio of 
the light it emits to the power it consumes. In the case of an incandescent 
lamp, this ratio might be expressed in B. C. Lumens per watt at lamp 
terminals. 

90. The specific consumption of a lamp should be the reciprocal of its 
efficiency, or the watts per B. C. Lumen. 

O*. The consumption per horizontal candle-power of a lamp is the ratio 
of power consumed at terminals to the mean horizontal candle-power, or 
watts per mean horizontal candle-power. 

OS. The Hefner-Alteneck amyl-acetate lamp is, in spite of its unsuitable 
color, the standard luminous source generally used in accurate photo- 
metric measurements. In comparing lamps with this standard, the ratio of 
the horizontal intensities of the Hefner and British candles maybe accepted 
conventionally as follows : 1 Hefner under Reichsanstalt standard condi- 
tions =0.88 British candle. 



APPENDIX I. 

Efficiency of Phase-Displacing- Apparatus. 

In apparatus producing phase displacement, as, for example, synchronous 
compensators, exciters of induction generators, reactors, condensers, polari- 
zation cells, etc., the efficiency should be understood to be the ratio of the 
volt-ampere activity to the volt-ampere activity plus power loss. 

The efficiency may be calculated by determining the losses individually, 
adding to them the volt-ampere activity, and then dividing the volt-ampere 
activity by the sum. 

1st. In synchronous compensators and exciters of induction generators, 
the determination of losses is the same as in other synchronous machines 
under Sections 11 and 12. 

2d. In reactive coils the losses are molecular friction, eddy losses, and 
I 2 r loss. They should be measured by watt-meter. The efficiency of re- 
active coils should be determined with a sine wave of impressed E.M.F., 
except where expressly specified otherwise. In reactive coils the load 
losses may be considerable. 

3d. In condensers the losses are due to dielectric hysteresis and leakage, 
and should be determined by watt-meter with a sine wave of E.M.F. 

4th. In polarization cells the losses are those due to electric resistivity 
and a loss in the electrolyte of the nature of chemical hysteresis, and are 
usually very considerable! They depend upon the frequency, voltage, and 
temperature, and should be determined with a sine wave of impressed 
E.M.F. , except Avhere expressly specified otherwise. 

APPENDIX II. 

Apparent Efficiency. 

In apparatus in which a phase displacement is inherent to their operation 
apparent efficiency should be understood as the ratio of net power output to 
volt-ampere input. 

Such apparatus comprise induction motors, reactive synchronous con- 
verters, synchronous converters controlling the voltage of an alternating- 
current system, self-exciting synchronous motors, potential regulators, and 
open magnetic circuit transformers, etc. 



REPORT OF COMMITTEE ON STANDARDIZATION. 305b 



Since the apparent efficiency of apparatus generating electric power de- 
pends upon the power factor'of the load, the apparent efficiency, unless 
otherwise specified, should be referred to a load-power factor of unity. 

APPENDIX III. 

Power factor and Inductance factor. 

The power factor in alternating circuits or apparatus may be defined as 
the ratio of the electric power, in watts, to volt-amperes. 

The inductance factor is to be considered as the ratio of wattless volt- 
amperes to total volt-amperes. 

Thus, if p = power factor, q — inductance factor, 
then, with a sine wave of E.M.F. p 2 =: q 2 =. 1. 
The power factor is the 

(energy component of current, or E.M.F.) _ true power 
(total current, or E.M.F.) — volt-amperes' 

and the inductance factor is the 

(wattless component of current, or E.M.F.) 
(total current, or E.M.F.) 

Since the power-factor of apparatus supplying electric power depends 
upon the power-factor of the lpad, the power-factor of the load should be 
considered as unity, unless otherwise specified. 



APPENDIX IV. 

The following notation is recommended : — 

E, e, voltage, E.M.F., potential 

difference, 
/, i, current, 
P, power, 
<j), magnetic flux, 
$, magnetic density, 
R, r, resistance, 

Vector quantities, when used, should be denoted by capital italics. 



x, reactance, 
Z, z, impedance, 
L, I, inductance, 
C, c, capacity, 
Y, y, admittance, 
b, susceptance, 
g, conductance. 



APPENDIX V. 

Table of sparking distances in air between opposed sharp needle-points, 
for various effective sinusoidal voltages, in inches and in centimeters. 



Kilovolts. 


Distance. 


Kilovolts. 


Distance. 


Sq. Root of 






Sq. Root of 






VIean Square. 


Inches. 


Cms. 


Mean Square. 


Inches. 


Cms 


5 


0.225 


0.57 


60 


4.65 


11.8 


10 


0.47 


1.19 


70 


5.85 


14.9 


15 


0.725 


1.84 


80 


7.1 


18.0 


20 


1.0 


2.54 


90 


8.35 


21.2 


25 


1.3 


3.3 


100 


9.6 


24.4 


30 


1.625 


4.1 


110 


10.75 


27.3 


35 


2.0 


5.1 


120 


11.85 


30.1 


40 


2.45 


6.2 


130 


12.95 


32.9 


45 


2.95 


7.5 


140 


13.95 


35.4 


50 


3.55 


9.0 


150 


15.0 


38.1 



306 TESTS OF DYNAMOS AND MOTORS. 



TESTS OF 1>1' X.l.UOft AflTO MOTORS. 

All reliable manufacturers of electrical machinery and apparatus are now 
provided with the necessary facilities for testing the efficiency and other 
properties of their output, and where the purchaser desires to confirm the 
tests and guaranties of the maker, he should endeavor to have nearly, and 
in some cases all such tests carried out in his presence at the factory, unless 
he may be equipped with sufficient facilities to enable him to carry out like 
tests in his own shops after the apparatus is in place. 

Some tests, such as full load and overload, temperature, and insulation 
(except dielectric) tests are best made after the machinery has been installed 
and is in full running order. 

Owing to the ease and accuracy with which electrical measurements can 
be made, it is always more convenient to make use of electrical driving 
power for dynamos, and electrical load for the dynamo output, and in the 
case of motors, a direct-current dynamo with electrical load makes the best 
load for belting the motor to. 

No really accurate tests of dynamo efficiencies can be made with water- 
wheels, and only slightly better are those made by steam-engines, owing 
to unreliability of friction cards for the engine itself and the change of fric- 
tion with load. 

' Where it is necessary to use a steam-engine for dynamo testing, all fric- 
tion and low load cards should be taken with the steam throttled so low as 
to cut off at more than half stroke, and to run the engine at the same speed 
as when under load. 

The tests of the engine as separated from the dynamo are as follows : — 

a. Friction of engine alone. 

b. Friction of engine and any belts and countershaft between it and the 
dynamo under test. 

Consult works on indicators and steam-engines for instructions for deter- 
mining power of engines under various conditions. 

The important practical tests for acceptance by the purchaser, or to deter- 
mine the full value of all the properties of dynamos and motors, are to learn 
the value of the following items : — 

Rise of temperature under full load. 

Insulation resistance. 

Dielectric strength of insulation. 

Regulation. 

Overload capacity. 

Efficiency, core loss. 

Bearing friction, windage and brush friction. 

I 2 E loss in field and field rheostat, 
I 2 R loss in armature and brushes. 

Note. — If a separate exciter goes with the dynamo, its losses will be 
determined separately as for a dynamo. 

Methods of determining each of the above-named items will be described, 
and then the combinations of them necessary for any test will be outlined. 

Temperature. — The rise of temperature in a dynamo, motor, or 
transformer, is one of the most important factors in determining the life of 
such piece of apparatus; and tests for its determination should be carried 
out according to the highest standards that can be specified, and yet be 
within reasonable range of economy. The A. I. E. E. standards state the 
allowable rise of temperature above surrounding air for most conditions, 
but special conditions must be met by special standards. For instance, no 
ordinary insulation ought to be subjected to a degree of heat exceeding 
212° F., or 100° C. And yet in the dynamo-room of our naval vessels the 
temperature is said to at times reach'l30° F., or even higher, which leaves a 
small margin for safety. It is obvious that specifications for dynamos in 
such locations should call for a much lower temperature rise in order to be 
safe under full load. 

For all practical temperature tests it is sufficient to run a machine under 
its normal full-load conditions until it has developed its highest temperature, 
although at times a curve of rise of temperature may be desired at various 
loads. 



TEMPERATURE. 307 



All small dynamos, motors, and transformers, up to, say, 50 KW., will 
reach maximum temperature in rive hours run under full load, if the tem- 
perature rise is normal ; but larger machines sometimes require from 6 to 18 
hours, although this depends quite as much on the design and construction 
of the apparatus as on size, as, for instance, the 5,000 h.p. Niagara Falls Gen- 
erators reach full temperature in five hours. Temperature tests can be 
shortened by overloading the apparatus for a time, thus reaching full heat 
in a shorter period. 

On dynamos and motors the temperatures of all iron or frame parts, com- 
mutators, and pole-pieces, have to be taken by thermometer laid on the 
surface and covered by waste. Note that when temperatures are taken 
with the machine running, care must be taken not to use enough waste to 
influence the machine's radiation. Where there are spaces, as air spaces, 
in armature cores or in the field laminations, that Avill permit the insertion 
of a thermometer, it should be placed there. Temperature of field coils 
should be taken by thermometer laid on the surface and covered with waste, 
and by taking the resistance of the coils first at the room temperature and 
again\vhile hot immediately after the heat run. Temperature rise of arma- 
ture windings can be taken by surface measurement and by the resistance 
method also ; although being nearly always of low resistance, very careful 
tests by fine galvanometer and very steady current are required in order to 
get anything like accurate results. 

The formula for determining the rise of temperature from the rise of 
resistance is as follows : — 

Temperature Ity rise in resistance; for copper. — The in- 
crease in resistance due to increase in temperature is 0.4% for each degree 
Cent, above zero, the resistance at zero being taken as the base. If then 

i{ =s temperature of copper when cold resistance is measured, 
i? : = resistance at temperature t{, 

t 2 = temperature of copper when hot resistance is taken, 
R 2 z= resistance at temperature t 2 , 
Then first reducing to zero degrees, we have 

S ° = 1 + .004 t, (1) - 

The increase in resistance from to t 2 degrees is R 2 — R , an d hence we 
have for final temperature, 

n r> 

h = -^ — -° -T- -004 (2). 

Substituting (1) 

_ X i (l + .00it i )-R t 
h ~ iOO^ (3) - 

It is usually most convenient to correct all cold resistances to a tempera- 
ture of 20° C, in which case we first reduce to zero and then raise to 20°. 
The general formula for obtaining the resistance at t degrees is 

Rt = (1 -4- .004 t) E . 
Hence R 20 = 1.08 R and in terms of the cold resistance at temperature t. 
_ (1-08 R ) 
2 ~ (1 + .004 t) W ' 

Formula (3) then becomes, when the cold resistance is at 20°, 
1.08 R„ 1 R 9 

t * = m x iC-m= 270 iC ~ 250 (5) - 

As the first formula requires but one setting of the slide rule, and the sub- 
traction of the constant 250 can usually be done mentally, the advantage of 
the temperature equation in this form is very great as regards both speed 
and accuracy. 

The temperature co-efficients most generally are 

For copper 004 

Resistivity of copper = .000001595 per cubic Cm. 
Resistivity of G. S. = .00003468 per cubic Cm. 



308 'TESTS OF DYNAMOS AND MOTORS. 



The following parts should be tested by the resistance method and the 
surface method also : 

Field coils series, and shunt. 

Armature coils. In 3-phase machines, take resistance between all three 
rings. 

On transformers which are enclosed in a tank filled with oil, temperatures 
by thermometer should be taken on — 

Outside case, in several places. 

Oil, on top, and deeper by letting down thermometer. 
Windings, by placing thermometer against same, even if under oil. 
Laminations, by placing thermometer against saane, even if under oil. 
Terminals. 

Room, as with dynamos and motors. 

Also resistance measurements of primary and secondary windings, from 
which the temperature by resistance can be calculated as shown. 

On transformers cooled by air forced through spaces between windings 
and spaces in laminations, temperatures by thermometer should be taken 
on — 

Outside frame. 

Air, outgoing from coils. 

Air, outgoing from iron laminations. 

Windings. 

Terminals. 

Room, in two or more places. 

Also resistance measurements, hot and cold, should be taken, from which 

rise of temperature, by resistance can be calculated. 
Finally, the cubic feet of air, and pressure to force same through spaces 

(easily measured by " U " tube of water), should be measured. 

When other fluids are used for cooling, such as water passing through 
piping submerged in oil, in which also the windings and core are submerged, 
or through windings of transformers themselves (made hollow for the pur- 
pose), the temperature of incoming and outgoing fluid should be measured, 
the quantity used and the pressure necessary to force it through the path 
arranged, besides the other points mentioned above. 

The following parts should be tested by thermometer on the surface : — 

Room, on side opposite from steam-engine, if direct connected, and always 

in two or more parts of the room, within six feet of machine. 
Bearings, each bearing, thermometer held against inner shell, unless oil 

from the well is found to be of same temperature as the bearing. 
Commutators and collector rings. 

Brush-holders and brushes, if thought hotter than the commutator. 
Pole-tips, leading and following. 
Armature teeth, windings, and spider. 
Field frame. 
Terminal blocks, for leads to switch-board, and those for leads from the 

brushes. 
Series shunt, if in a compound-wound machine. 
Shunt field rheostat. 

Careful watch of thermometers is necessary in all cases, as they will rise 
for a time and then begin to fall ; and the maximum point is what is wanted. 

British authorities state a definite time to read the thermometers after 
stopping the machine. 

Care must also be taken to stop the machine rotating as soon as possible, 
so that it will not fan itself cool. 

A handy method of constructing a curve showing the rise of temperature 
in the stationary parts of a machine at full load is to insert a small coil of 
fine iron wire in some crevice in the machine in the part of which the tem- 
perature is desired. Connect the coil with a mirror galvanometer and 
battery. 

The temperature coefficient of iron is high, and the gradual increase in 
resistance of the coil will cause the readings on the galvanometer to grow 
gradually less ; and readings taken at regular intervals of time can be 
plotted on cross-section paper to form a curve showing the changes in 
temperature. 



TEMPERATURE. 309 

Record* of temperature test. — During all heat runs, which 
should, be on non-inductive load, such as a water-box, readings should be 
taken every fifteen (15) minutes of the following items. 

On direct and alternating current motors and generators — 
Armature, Volts (between the various rings where machine is more than 
single-phase, in the case of alternators, and between brushes, 
in the case of a D. C. machine). 
Amperes (in each line). 
Speed. 
Field, Volts. 

Amperes. 
On synchronous converters : — 
Armature, Volts (between all rings on A. C. end, and between brushes on 
D. C. end). 
Amperes, per line A. C. end, also D. C. end. 
Speed. 
Field, Volts. 

Amperes. 
On transformers, compensators, potential regulators : — 
Volts, primary. 
Volts, secondary. 
Amperes, primary. 
Amperes, secondary. 
Cycles. 

Amount and pressure of cooling-fluid (if any is used). 
On induction motors : — 

Volts, between lines. 
Amperes, in line. 
Speed. 
Cycles. 
Overload. — The A. I. E. E. standards contain suggestions for overload 
capacity (see page 303). 

The writer has uniformly specified a standard overload of 25% for 3 hours, 
and there seems to be no especial difficulty in getting machines for this 
Standard that do not heat dangerously under such conditions. 

Insulation test. — Insulation resistance in ohms is of much less im- 
portance than resistance against breakdown of the insulation under a 
strain test, with alternating current of high pressure. 

Make all insulation tests with a voltage as high, at least, as that at which 
the machine is to be worked. 

The following diagram shows the connections to be made with E some 
external source of E.M.F. Tbe formula used is 
R = resistance of voltmeter. 

E = E.M.F. across dynamo terminals. mmm 

e = reading of voltmeter connected as in 
diagram. 

x =. insulation resistance in ohms. 



ARMATURE 3s£ 

o 



Th«U'«-=JB(f-ij. /__X 



According to the A. I. E. E. standards, FBAMB 

the insulation resistance must be such that Fig. 1. Connections for volt- 
the rated voltage of the machine will not meter test of insulation re- 
send more than T (joiooo of tne full-load cur- sistance of a dynamo, 
rent through the insulation. One megohm 

is usually considered sufficient, if found by such a test. Where one megohm 
is specified as sufficient, the maximum deflection that will produce that 
value, and that must not be exceeded in the test, may be found by the fol- 
lowing variation of the above formula : 

_ RX E 
e ~ 1,000,000 + R 

Strain test. — The dielectric strength of insulation should be deter- 
mined by a continued application of an alternating E.M.F. for at least one 
(1) minute. The transformer from which the alternating E.M.F. is taken 
should have a current capacity at least four (4) times the amount of current 



310 



TESTS OF DYNAMOS AND MOTORS. 




ARMATURE 



Fig. 2. Connections for strain 
test of dynamo or motor or 
transformer insulation. 



necessary to charge the apparatus under test as a condenser. Strain tests 
should only be made with the apparatus fully assembled. 
Connect on a D.C. machine as in the following diagram. 

Strain tests should be made with a sine 
wave of E.M.F., or with an E.M.F. having 
the same striking distance between needle 
points in air. 

See article 40 A. I. E. E. standards for 
proper voltages. 

Regulation. — The test for regula- 
tion in a dynamo consists in determining 
its change in voltage under different 
loads, or output of current, the speed be- 
ing maintained constant. 

The test for regulation in a motor 
consists in determining its change of 
speed, under different applied loads, 
when the voltage is kept constant. 

Standards. — For full details of standards of regulation of different 
machines, see report of the Committee on Standardization of the A. I. E. E. 
at the beginning of this chapter. 

Regulation Vests, Dynamos, Shunt or Compound, and 
Alternators. 

The dynamo must be run for a sufficient length of time at a heavy load to 
raise its temperature to its highest limit ; the field rheostat is then adjusted, 
starting with voltage a little low, and bringing up to proper value to obtain 
the standard voltage at the machine terminals, and since a constant temper- 
ature condition has been reached, must not again be adjusted during the 
test. Adjust the brushes, in the case of a D. C. machine, for full-load con- 
ditions, and they should not receive other adjustment during the test. This 
is a severe condition, and not all machines will stand it ; but all good dy- 
namos, with carbon brushes, will stand the test very well, provided the 
brushes are adjusted at just the non-sparking point at no load. 

Load is now decreased by regular steps, and when the current has settled 
the following readings are taken : — 

Speed of dynamo (adjusted at proper amount). 

Current in output (a non-inductive load should be used). 

If alternator, current in each line if more than single-phase. 

Volts at machine terminals. 

Amperes, field. 

Volts, field. 

Note sparking at the brushes (they should not spark any with carbon 

brushes). 

Readings should be taken for at least ten intervals, from full load to open 

circuit (no load) ; and load should then be put on gradually and by the same 

steps as it was brought down ; and the same records should be made back 

to full-load point, and beyond to 25% overload. 

If the readings are to be plotted in curves, as they always should be, it 
will make little difference if the intervals or steps are not all alike ; and 
should the steps be overreached in adjusting the load, the load must not, in 
any circumstances, be backed up or readjusted back to get regular inter- 
vals or a stated value, as the conditions of magnetization change, and throw 
the test all out. In case the current is broken, or the test has to be slowed 
down in speed or stopped, it must be commenced all over again. Finally, 
when the curves are plotted, draw, in the case of a compound-wound ma- 
chine, a straight line joining the no-load voltage and the full-load voltage ; 
and the ratio of the point of maximum departure of the voltage from this 
line to the voltage indicated by the line at the point will be the regulation 
of the machine. 

The readings as obtained give what is called a field compounding curve. 
In the case of a shunt or separately excited machine, the procedure for the 
test is the same ; but when the curve is plotted, the regulation is figured as 
equal to the difference between the no-load voltage and full-load voltage, 
divided by the full-load voltage. The curve is called a characteristic in 
this case. 



DYNAMO EFFICIENCY. 



311 



Regulation Tests, Motor*, Shunt, Compound, and 
Induction. 

After driving the motor under heavy load for a length of time sufficient 
to develop its full heat, full-rated load should be applied, the field rheostat, 
if any is used, and brushes adjusted for the standard conditions ; then the 
load should be gradually removed by regular steps, and the following read- 
ings be made at each such step : — 
Amperes, input. 

Volts at machine terminals (kept constant). 
Watts, if induction motor. 
Speed of am ature. 
Note sparking at brushes. 
Amperes, field (in D. C. machines). 
At least ten steps of load should be taken from full-rated load to no load. 
The ratio of the maximum drop in speed between no-load and full-load, 
which will be at full-load, to the speed at full-load, is the regulation of the 
motor. 

Efficiency Tests. Dynamos. 

The term efficiency has two meanings as applied to dynamos ; viz., electrical 
and commercial. The electrical efficiency of a dynamo is the ratio of elec- 
trical energy delivered to the line at the dynamo terminals to the total electri- 
cal energy produced in the machine. The commercial efficiency of a dynamo 
is the ratio of the energy delivered at the terminals of the machine to the total 
energy supplied at the pulley. Otherwise the electrical efficiency takes into 
account only electrical losses, while the commercial efficiency includes all 
losses, electrical, magnetic, and frictional. 



Core-Loss Test, and Test for friction and "Windag-e. 

These losses are treated together for the reason that all are obtained at 
the same time, and the first can only be determined after separating out the 
others. 

A core-loss test is ordinarily run only on new types of dynamos and 
motors, but is handy to know of any machine, and if time and the facilities 
are available, should be run on acceptance tests by the consulting engineer. 
It consists in running the armature at open circuit in an excited field, driv- 
ing it by belt from a motor the input to which, after making proper deduc- 
tions, is the measure of the power necessary to turn the iron core in a field 
of the same strength as that in which it will work when in actual use. 

Connect as in the following diagram, in which A is the dynamo or motor 
under test, and B is the 
motor driving the arma- 
ture of A by means of 
the belt. The field of A 
must, of necessity, be 
separately excited, as 
its own armature circuit 
must be open so that 
there may be no current 
generated in its conduc- 
tors. 

The motor field is sep 




MOTOR KIELD 
EXCITER 



DYNAMO 
UNDER TEST 



GENERATOR EOR 
MOTOR CURRENT 



Fig. 3. Connections for a test of core loss. 



arately excited and kept constant, so that its losses and the core loss of the 
motor itself , being constant for all conditions of the test, may be cancelled 
in the calculations. The motor B should be thoroughly heated ; and bear- 
ings should be run long enough to have reached a constant friction condi- 
tion before starting this test, so that as little change as possible will take 
place in the different " constant" values. It is necessary to know accu- 
rately the resistance of the armature, B, in order to determine its 1*R loss 
at different loads, and to use copper brushes to practically eliminate tne 

It is well to make a test run with the belt on in order to learn at what 
speed it is necessary to run the motor in order to drive the armature A at its 
proper and standard speed. 



312 



TESTS OF DfNAMOS AND MOTORS. 



Fraction, core loss, and windag-e of motor. — The speed having 
been determined, the belt is removed, and the motor field kept at its final 
adjustment, and enough voltage is supplied to the motor armature to drive 
it free at the standard speed. The watts input to the armature is then the 
measure of the loss (I 2 li) in the motor armature plus the friction of its bear- 
ings, plus its windage, plus core loss, or the total loss in the motor at no 
load. This is called the " running light " reading. 

Friction and niiulag'« of dynamo. — After learning the losses 
in the driving motor, the belt is put on and the dynamo is driven at its 
standard speed without excitation, and in order to be sure of this a volt- 
meter may be connected across the armature terminals ; if the slightest 
indication of pressure is -found, the dynamo field can be reversely excited, 
to be demagnetized, by touching its terminals momentarily to a source of 
E.M.F. Take a number of readings of the input to the motor in order to 
obtain a good mean, and the friction and windage of dynamo is then the 
input to the motor, less the "running light" reading previously obtained, 
the I 2 R of motor armature having been taken out in each case. 

Let W x = watts input to motor, 

n x = I-R in motor armature when driving dynamo, 
/=" running light" reading of motor, 
}\ — friction and windage of dynamo armature, 
n % = £ 2 R of motor armature when " running light," 
then /j = }\\ — (% +/ +f % + « 2 ). 

Brush friction. — The friction of brushes is ordinarily a small portion 
of the losses ; hut when it is desirable that it should be separated from other 
losses, it can he done at the same time and in the same manner as the test 
for bearing friction. The brushes can be lifted free from the commutator 
or collector rings when the readings of input to the driving motor for bearing 
friction are taken ; dropping the brushes again onto the commutator and 
taking other readings, the difference between these last readings and those 
taken with brushes off will be the value of brush friction. Note, that allow- 
ance must be made as before for increase of I 2 E loss in the motor armature. 

Test for core loss. — Having determined the friction and other losses 
that are to be deducted from the total loss, a current as heavy as will ever 
he used is put on the dynamo field, the motor is supplied with current 
enough to drive the dynamo at its standard speed, and the reading of watts 
and current input to the motor armature is taken. 

The dynamo field current is now gradually decreased in approximately 
regular steps, readings of the input to the motor being taken at each such 
step until zero exciting current is reached, when the exciting current is 
reversed and the current increased in like steps until the highest current 
reading is again reached. This may now be again decreased by intervals 
back to zero, reversed and increased back to the starting-point, which will 
thus complete a cycle of magnetization ; ordinarily this refinement is not, 
however, necessary. 

This test must always be carried through without stop ; and although it is 
desirable to make the step changes in field excitation alike, if the excitation 
be changed in excess of the regular step it must not be changed back for the 
purpose of making the interval regular, as it will change the conditions of 
the residual field. "When the readings are plotted on a curve, regularity in 
intervals of magnetization is not entirely necessary. 

The following ruling makes a convenient method of tabulation : — 



Dtnamo. 


Motor. 


Speed 


amperes 

in 

field 


Speed 


amperes 

in 

field 


amperes 

in 

armature 

i 


volts 

in 

armature 

e 


Constant 




Constant. 


Constant. 







DYNAMO EFFICIENCY. 
Computations. 



313 



watts in 

armature 

belt on 

W„ = i e 



Running 

light 

reading 

/ 



I 2 R 

in arm. 
belt on 



in arm. 
belt off 



Core loss 



Plot on curve with exciting-current values on the horizontal scale, and 
the core loss on the vertical, and the usual core-loss curve is obtained. 



Separation of core loss into Hysteresis and Eddy 
current loss. 

Losses due to hysteresis and friction vary directly with the speed ; losses 
due to eddy currents vary as the square of the speed. 

Current and voltage must now be applied to the dynamo armature to 
drive it as a motor at proper speed, with the current in the separately 
excited field kept constant at proper value. Drive the motor (dynamo) at 
say two different speeds, one of which may be K times the other ; let 

L == total loss in watts, 

f, = loss in friction, 

H— loss by hysteresis, 

D = loss by eddy currents, or 

L*=fj-\- H-\- D at the first speed, 

L, = Kf, + KH-\- K 2 D at second speed, 
Kx(l) = KL = K?\ + kH + AD, 
(2) — (3) = L,— KL = K 2 D — KD, 



UK: 



L x — KL 
D 
2, then 

D; 



KD(K-l), 
L, — KL 



K(K-1) 



2i 



L. 



2 (2 — 1 ) 

Kapp and Housman separately devised the above method of separating 
the losses, but stated them somewhat differently. 

With the field separately excited at a constant value, different values of 
current are supplied to the armature at different voltages, to drive it as a 
motor. The results are plotted in a curve which is a straight line, rising as 
the volts are increased. 

The following diagram shows how the losses are plotted in curves. The 
test as a separately excited motor is run at a number of different values of 
voltage and current in the armature, and the results are plotted in a curve 
as shown in the following diagram. The line a, b, is plotted from the results 
of the current and volt readings. 

The line a, c, is then drawn parallel to the base, and represents the sum 
of all the other losses, as shown by previous tests, and they may be further 
separated and laid off on the chart. 

Foucault currents are represented in value by the triangle a, c, b. 

If another run be made with a different value of excitation, a curve, a x , b lt 
or one below the original a, b, will be gotten, according to whether the total 
losses have been increased or decreased. 

If the higher values of current tend to demagnetize, by reason of the eddy 
currents in the armature, the curve a, b, will curve upward somewhat at the 
upper end. 

It is thus seen how to measure core-loss, and friction and windage of a 
dynamo; knowing this and the resistance of the various parts, the efficiency 
is quickly calculated, thus 

Let JF= core-loss + friction (obtained as shown), 
V =z voltage of armature, 
/= current of dynamo armature, 
i, =r current of dynamo field, 
i? = resistance of armature and brushes, 
JR. = resistance of field. 



314 



TESTS OF DYNAMOS AND MOTORS. 



only 
Vc 



losses (i.e., neglecting rheo- 




HYSTERES.IS 



Then considering the above as the 
stats, etc.), 

Efficiency = ^- f - 72i2 + /i2i2i _ f 

This is the simplest method of getting the efficiency, but does not take in 

"load losses" if any 
should exist. 

Another test for 
efficiency. — If the dy- 
namo under test is not of 
too large capacity, and a 
load for its full output is 
available, either in the 
form of a lamp bank, 
water rheostat, or other 
adjustable resistance, 
then one form of test is 
to belt it to a motor. 

By separately exciting 
the motor fields, and run- 
ning the motor free with 
belt off, its friction can 
be determined, and with 
the resistance of the ar- 
mature known, the input 
to the motor in watts, 
less the friction and the 
I 2 B loss in its armature 
at the given load, is a di- 
rect measure of the 
power applied at the pul- 
ley of the dynamo. The 
output in watts, meas- 
ured at the dynamo terminals, then measures the efficiency of the machine. 
Let, 

TV = watts input to motor, 

I = losses in motor, friction, J 2 /?, and core-loss, 
W^ = watts output at dynamo terminals. 



BOSH FRICTION 



BESRINQ. ERICTfCN AND WINDAGE 



O, VOLTS IN ARMATURE w 

Fig. 4. Diagram showing separation of losses 
in dynamos. 



of efficiency = 100 X 



W 



W- 



= commercial efficiency. 



Knowing the current flowing in the armature and in the fields, and also 
knowing the resistance of the same, the l-R losses in each may be calcu- 
lated, which, added to the output at the dynamo terminals, shows the total 
electrical energy generated in the ma- 
chine. 

If m = the 1 2 R loss in the armature, 
/= the I 2 R loss in the fields, 

The electrical efficiency will be 
% electrical efficiency 



100 X 



Wy + TO + / 




GENERATOR 
UNDER TEST 



GENERATOR 



WATER 
RHEOSTAT. 
=/ FOB LOAD 



The following diagram shows the 
connections for this form of test. 

It must be obvious that a steam-en- 
gine, or other motive power that can 
be accurately measured, may be used 
in place of the electric motor ; but 
measurements of mechanical power 
are so much more liable to error that 
they should be avoided where possible. 

The only objection to this method 
is that the friction of the driving-motor varies with the load, and the loss 
in the belt is not considered. 



Fig. 5. Connections for efficiency 
test of a generator. Driven by an 
electric motor. 



DYNAMO EFFICIENCY. 



315 



Kapp's Test witlt two Similar Dynamo*. 

Where two similar dynamos are to be tested, and especially where their 
capacity is so great as to make it difficult to supply load for them, it is com- 
mon to test them by a sort of opposition method ; that is, their shafts are 
either coupled or belted together, the armature leads are connected in series, 
the field of one is weakened enough to make a motor of it ; this motor drives 
the other machine as a generator, and its current is delivered to the motor. 
The difference in currents between the two machines, and for exciting the 
fields of each, is supplied by a separate generator. 

The following diagram shows the 
method of connecting two similar dyna- 
mos for Kapp's test. D, is the dynamo ; 
M, the machine with field weakened by 
the resistance R, that acts as a moter, and 
G, is the generator that supplies the en- 
ergy necessary to make up the losses, ex- 
citation, and differences. 

Start the combination and get them to 
standard voltage, as shown by the volt- 
meter ; then take a reading of the cur- 
rent with the switch on b, and another 
with the switch on a. Let the first read- Fig. 6. Connections for Kapp's 
ing be m, and the second d, and let x be method of efficiency test of two 
the efficiency of either machine, then similar dynamos. 

% efficiency of the combination = 100 X -?> and 




*=V(i» x -) 



>!M, 




In using this formula the efficiency of the dynamo at its load is assumed 
the same as the motor at its simultaneous load, which is usually true above 
the | load point. The loss in motor-field rheostat should also be allowed for. 
Another similar method, called "pumping back," ig to connect the shafts 
of the two machines as before, by clutch or belt ; arrange the electrical 
connections and instruments as in the following diagram. 
D is the dynamo under test ; M is the similar machine used as a motor ; 
and G is the generator for supplying cur- 
rent for the losses and differences be- 
tween M and D. The speed of the 
combination, as well as the load on D, 
can be adjusted by varying the field of M. 
The motor, M, drives D by means of 
the shaft or belt connection. M gets its 
current for power from two sources, viz., 
G and D. In order to determine the 
amount of mechanical power developed 
by M, and also to be able to separate the 
magnetic and frictional losses in the two 
machines, a core-loss test should have 
been made on the machine M at the same 
speed, current, and E.M.F. as it is to have in the efficiency test. The loss 
in the cable connections between M and D must also be taken into account, 
and is equal to the difference in volts between voltmeters c, and b, X the 
current flowing in ammeter n. 
Let V— E.M.F. of D, shown on c, 

V, — E.M.F. of M by vm. b, 
V„— E.M.F. of G by vm. a, 
1= amperes current from D by am. n, 
I t = amperes current from G by am. Z, 
I y/ =z amperes current in M = I-\- I n 
e = drop in connections between D and M = V — V m 
L = loss in connections between D and M. = e x I, 
r — D's internal resistance, 
r x — M's internal resistance, 

w = core loss -j- armature loss -f- field loss + friction of M in 
watts -J- L (loss in connections). 



Fig. 7. Efficiency test of two 
similar dynamos. 



16 



TESTS OF DYNAMOS AND MOTORS. 



Then 

W— the useful output of D = V X I, 
W, = energy supplied by G = V fl X I,, 
W -\- Wj = total energy supplied to M, 
W -j- Wj — w =z energy required to drive D, 

% commercial efficiency of D : 



I' 2 r = electrical loss in D, 
% electrical efficiency = 



W + Wj 

W 



x 100. 



., X 100. 
W + I 2 r 

The other way of calculating the efficiency with this arrangement is to 
measure the output =± W x from G, with full load on D. W x then is the 
losses of both machines under load ; and knowing the I 2 R loss in the arma- 
ture and field of each, the efficiency is quickly and accurately calculated. 
This method is best, as no core loss is required, and includes the " load 
losses." 

EIXCTHICAI HETHOD OF STTPPJL ITIlfO- THE 

LOiiEi AT C©]¥STJL]¥T POXEUTXIAJL. 

Modification of " Kapp Method," by Prof. Won. I, Puffer, from notes 

privately printed for the students of the Massachusetts institute 

of Technology . 

Specification. 

Two similar shunt dynamos under full load, one as a motor driving the 
other as a loaded dynamo through a mechanical coupling. Mains at same 
voltage as dynamos, and only large enough to supply the full-load losses of 
both dynamos. 

Line up the two dynamos carefully, and mechanically connect them by 
a good form of mecbanical coupling, strong enough to transmit the full load 
to the dynamo. 

Connect the field magnet windings of each machine to the supply mains, 
putting a suitable field rheostat in each. If desirable for any reason, the 
field of the dynamo may be left connected as designed ; but the field, of the 
motor, which does not in any way enter as a quantity to be measured during 
the test, should be connected to the supply mains. 




Fig. 8. Diagram of Connections for Professor Puffer's Modifi- 
cation of Kapp's Dynamo Test. 

IVKcthod of Starting-. 

Close the field circuit of the motor, and by the motor starting rheostat 
gradually bring the motor up to full speed. The dynamo armature will be 
also at proper speed and on open circuit. Now close the dynamo field and 
adjust the field rheostat until the dynamo is at about normal voltage. 
Adjust the speed roughly at first by the use of the field rheostat of the 
motor, remembering that an added resistance will cause tbe speed to rise. 
Next see that tbe voltage of the dynamo is equal to that of the motor, or, 
in other words, that there is no difference of potential between opposite 
sides of the main SAvitch on the dynamo, ("lose this switch and there may, 
<>r may not, be a .small current in the dynamo armature. Now carefully 



ELECTRICAL METHOD OF SUPPLYING LOSSES. oil 



increase the armature voltage of the dynamo, watching the ammeter, and 
weaken that of the motor ; a current will now from the dynamo to the 
motor, and the motor will transmit power mechanically to the dynamo. 

The current which was first taken from the supply wires to run the motor 
and dynamo armatures will increase somewhat. By a careful adjustment 
of the two rheostats and the lead on each machine, the conditions of full 
load of the dynamo may be produced. The motor is overloaded and its arm- 
ature will carry the sum of the dynamo and supply currents. Great care 
must be taken in adjusting the brushes of the macbines, because of great 
changes in the armature reactions which take place as the brushes are 
moved. It is well to remember that a backward lead to the motor brushes 
will increase the speed, as the armature reactions will considerably weaken 
the effective field strength. 

Cautious. 

The increase of speed will raise the dynamo voltage, and cause the cur- 
rent flowing in the armatures to greatly increase. A forward movement of 
the motor brushes will reduce both speed and current. A forward move- 
ment of the dynamo brushes will increase the armature reaction, and cut 
down the current through the armatures, while a backward movement will 
cause it greatly to increase. Very great care must be taken in adjusting 
the brush lead, as a movement of the brushes of either machine, which 
would be of little importance usually, will produce sometimes a change in 
current value equal to the full-load current. It is quite possible but poor 
practice to produce the load adjustment by use of the brushes alone. 

It is best to have ammeters of proper size in all circuits, but those actually 
required are in the dynamo leads and in the supply mains. A single volt- 
meter is all that is required. 

The field magnet circuits ought to be connected as shown, and the am- 
meters placed so that the energy in the fields does not come into the test of 
the losses in the armatures. The magnet of the machine under test, a 
dynamo in this case, should be under the proper electrical conditions for 
the load, yet not in the armature test, because the object of the test can best 
be made the determination of the stray power loss under the conditions of 
full load ; then having found this, assume the exact values of E, I, and 
speed, and so build up the data for the required efficiency under a desired 
set of conditions which might not have been exactly produced during the 
test. 

Immediately after the run, all hot resistances should be measured as 
rapidly and carefully as possible, to avoid any error due to a change in 
temperature. 

The energy given to the two armatures less the I 2 R in each armature, 
will be the sum of all the armature losses of the two dynamos under the 
conditions of the test, so that we measure directly the armature losses of 
the dynamos while fully loaded. 

It is evident that the two armatures are not under exactly the same con- 
ditions, except as to speed, for the dynamo armature will have an intensity 

of magnetic field that will give an armature voltage of Vf -f- Jj[i?^,while 

the motor will be weaker as Vf is the same for both armatures, and the 

motor armature voltage will be Vf — ^A^A All the iron core losses will be 
made much greater in the dynamo than in the motor. The motor armature 
must carry a current equal ito the sum of the dynamo and supply currents, 
and will get much hotter ; its reaction will also'be greater, and there will be 
a tendency for greater sparking at the brushes. 

The total stray power thus obtained may be divided between the two 
armatures equally, but preferably in proportion to the armature voltages, 
unless the true law for the armatures is known. All resistances of wires, etc., 
must be noted and corrections applied, unless entirely negligible. 

Two 15-H.P. dynamos were tested by the class of '93, using tbis method. 
One of the full-load tests is here given as a sample of calculation. The 
exact rating of the dynamos is not known, but is nearly 45 amperes at 220 
volts, with the dynamo at a speed of 1600 r.p.m. 



318 



TESTS OF DYNAMOS AND MOTORS. 



The averages of the ohserved readings taken during the test, and after 
run of about five hours to become heated, was as below. 



Example of Calculation. 

(Connections as shown in Fig. 8.) 

Volts at supply point ...... . . 220.3 

Amperes of 15.71 

Output of dynamo, amperes 45.80 

Dynamo field current . . . . . . . . 1.945 

Speed 1594. 

To Measure Armature Resistance. 

Motor V— 1.952 7=10.18 

Dynamo V— 2.406 7=10.08 

The motor field is out of the test while the dynamo field is in the test. 



Calculation. 




Watts supplied 220.3 x 15.71 = 3461. 




.3430= V 
.1962 = 7 




.5392 = 3461 
Dynamo armatures R. = Motor armature R. 


— 


2.406 .3813 R 1.952 .2905 
lOToS - 0035 ad 10J8 - 0077 

.3778 = 0.2387 .2828 : 


R 

am 

- 0.1918 


2 2 

I * R * I R 
ad ad am am 




la = 45.80 + 1.94 = 47.74 7« = 45.80 + 15.71 = 


:6151 


47.74* = (.6789 I 61.51* =( 7889 

( .6789 2 ( .7889 

R .2387= .3778 I R D i?.1918 .2828 

a a a 


72 i? M 
a a 


.7356 = 554.0 .8606 : 


= 725A 


Dynamo Field 




7=1.945 .2889 

V— 220.3 .3430 Field D 




.6319 = 428.4 




Watts supplied = 3461 
Dynamo field = 428.4 
72 7? M = 725.4 
72 7? D = 554.0 





Total heat lost = 1697.8 
Total stray power 



1763 



M and I). 



ELECTKICAL METHOD OF SUPPLYING LOSSES. 319 

Vad V am 

V t 4- l a R a 

47.74 X -2387 .6789 

.3778 
IR= 11.4 =.0567 
y t — 220.3 

231.7= V dd 208.5= V am 

Divide the total stray power between the two armatures as their 
armature voltages. 

Stray power dynamo. 

OICO 

231.7 



61.51 X .1918 


.7889 
.2828 


IR= 11.8 = 


.0717 


V t =220.3 





X 1763- 



231.7 + 208.5- -^ 

.3649 
Stray power dynamo = 928.0 = 1)675 
Stray power motor = 1763 — 928.0 = 835.0 

The quantity 928.0 is the object of our test, i.e., the stray power when 
as nearly as may be under actual running conditions. 

Calculation of Efficiencies. 

As run. 
Output of dynamo = 220.3 x 45.80 
.3430 



.0039 = 10090 


Watts output 


554 


I 2 *ad 


10090 428 

544 928 

_ 42 ? 11990 

11062 = Work done by current. 


Field 

Stray power 

Watts input to the dynamo. 


Eff. of Com. 

11062 
TT990 
Co mm, JEflF. 

10090 
11990 


.0437 
.0789 
.9648 = 92.2 per cent. 

.0039 

.0789 

^9250" = 84.1 per cent. 


Power required to run Dynamo. 


11990 
"746 


.0789 
.8727 
.2062 = 16.1 H. P. 



In this test, carbon brushes were used, and the lead adjusted as carefully 
as possible. If the exact rating of this dynamo had been 45 amperes and 220 
volts at a speed of 1600, and we wished to find the efficiencies corresponding, 
we should proceed in this way. 

The test was made under conditions as nearly as possible to the rating, 
and the stray power as found will not be perceptibly different from what it 
would be under the exact conditions. 

When the load has been as carefully adjusted as in this test, it is seldom 
worth while to make these corrections, as they are smaller than changes pro- 



320 



TESTS OF DYNAMOS AND MOTORS. 



duced by accidental changes of oiling, temperature, brush pressure, etc., 
of two separate tests. 

Advantages of the Method. 

Small amount of energy used in making the test, namely, only the losses. 
No wire or water rheostat required. Test made under full load, and yet 
the losses are directly measured. All quantities are expressed in terms de- 
pending on the same standards, and therefore the efficiency will be but little 
affected by any error in the standards. No mechanical power measure- 
ments are made, and all measurements are electrical. 



Disadvantages. 

Requires two similar machines. Armature reactions are not alike in both 
machines. Leads are not alike. Tbe iron losses are not the same. No belt 
pull on bearings. Must line up machines and use a good form of mechanical 
coupling. Sometimes difficult to set the brushes on the motor. The motor 
armature is much overloaded. 




RH. 
SEPARATE EXCITER 
FOR FIELDS 
OF MOTORS 



Fig. 9. Diagram of Connections for Test of Street Car 
Motors, Prof. Puffer. 




Fig. 10. Diagram of Connections of Modification of the 
Previous Diagram, by Prof. Puffer. 



This method is of advantage in the test of railway series motors, if slightly 
modified by the separate excitation of the motor fields. If the series field 



ELECTRICAL METHOD OF SUPPLYING LOSSES. 



windings be not separately excited there will be a great deal of unneces- 
sary difficulty from great changes of speed as tbe load is varied. However, 
one field may be kept in circuit on the machine used as a motor, as the test 
can then be made with the motor under its exact conditions. There will be 
a very great change of speed during adjustment of load, but there will be no 
danger of injuring anything, as the separate excitation of the dynamo field 
is an aid to steadiness. Railway motors, as generally made, will not stand 
their full rated load continuously, and the motor is likely to get too hot if 
not watched ; the machine used as a dynamo Avill run cold, as it will not 
have a large current in it. The friction of brushes is very large in these 
motors, and in general there is a want of accuracy in the division of the 
total stray power between the two armatures. It can only be very approxi- 
mately done by the aid of curves showing the relation between speed and 
stray power, and armature voltage and stray power. 



Hopkinson'* Test of two Similar* Dynamos. 

In the original Hopkinson method, the two dynamos to be tested were 
placed on a common foundation with their shafts in line, and coupled to- 
gether. The combination was then driven by a belt from an engine, or other 
source of power, to a pulley on the dynamo shafts. The leads of both ma- 
chines were then joined in series, and the fields adjusted so that one acted 
as a motor driven by current from the other. The outside power in that 
case supplied, and was a measure of the total losses in the combination, the 
efficiency of either machine being taken as the square root of the efficiency 
of the combination. 

Many modifications of this test have been used, especially in the substitu- 
tion of some method of electrically driving the combination, as the driving- 
power is so much easier measured if electrical. 

This test is someAvhat like that last given, but the two machines are con- 
nected in series through the source of supply for the difference in power, 

such as a storage battery or generator. 
The following diagram' shows the con- 
nections for the Hopkinson test, with 
a generator for supplying the differ- 
ence in power. 

In this test the output of G plus en- 
ergy taken by M t (motor driving the 
system), gives losses of motor and dy- 
namo (the losses of M x being taken out. 
These losses being known, the efficiency 
can be calculated. 

If the two machines D and M are 
alike, G supplies the I 2 E losses of ar- 
matures, and M the friction, core 
losses, and I 2 R of fields. 
Another method useful where load and 
current are both available, is to drive one of tAvo similar dynamos as a 
motor, and belt the second dynamo to it. Put the proper load on the dy- 
namo, and the efficiency of the combination is the ratio of the Avatts taken 
out of the dynamo to the Avatts supplied to the motor. The efficiency of 
either machine, neglecting small differences, is then the square root of the 
efficiency of both. 
If W= Avatts put into the motor, 

W, = watts taken from the dynamo, 
x = efficiency per cent of the combination, 
y =. efficiency of either machine. 




Fig. 11. Diagram of connections 
for Hopkinson' s test of tAvo sim- 
ilar dynamos. 



W, X 100 



W 



y = vi 



The above test is especially applicable to rotary converters, the belt being 
discarded, and the a c sides being connected by AA'ires ; thus the first ma- 
chine supplies alternating current to the second, which acts as a motor gen- 
erator Avith an output of direct current. The only error (usually small) is 



322 



TESTS OF DYNAMOS AND MOTORS. 



AM.//./ 





PRONY BRAKE 



due to the fact that both machines are not running same load, since that 
one supplies the losses of both. 

JFtemiu"-'* Modification of Hopkin- 

son Test. — In this case the two dynamos under 
test are connected together by belt or shafts, and 
are driven electrically by an external source of 
current, say a storage battery or another dynamo, 
which is connected in series with the circuit of 
the two machines. Figure 12 shows the con- 
nections for this test, which will be found car- 
ried out in full in Fleming's " Electrical Labo- 
ratory Notes and Forms." 

MOTOR TESTS. 

Probably the most common method of testing the efficiency and capa- 
city of motors is with the prony brake, although in factories where spare 
dynamos are to be had, with load available for them, there can be no 
question that belting the motor to the dynamo with an electrical load is 

by far the most accurate, and 

7 _j the easiest to carry out. 

T*i*oiiy brake test. — In 
this test a pulley of suitable 
dimensions is applied to the 
motor-shaft, and some form of 
friction brake is applied to the 
pulley to absorb the power. 
The following diagram shows 
-p lGr i one of the simplest forms of 

prony brake ; but ropes, straps, 
and other appliances are also often used in place of the wooden brake shoes 
as shown. 
Note. — See Flather, " Dynamometers and the Measurement of power." 
As the friction of the brake creates a great amount of heat, some method 
of keeping the pulley cool is necessary if the test is to continue any length 
of time. A pulley with deep inside flanges is often used ; water is poured 
into the pulley after it has reached its full speed, and will stay there by 
reason of the centrifugal force until it is evaporated by the heat, or the 
speed is lowered enough to let it drop out. Rope brakes with spring bal- 
ances are quite handy forms. 
The work done on the brake per m inute is the product of the following items : 
I = the distance from the centre of the brake pulley to the point 

of bearing on the scales, in feet, 
n = number of revolutions of the pulley per second, 
w = weight in lbs. of brake bearing on scales. 
Power = 2 it I n w = foot-pounds per second, and 
_ 2 7T In xv 
H - P> - 550 
The input to the motor is measured in watts, and can be reduced to horse- 
power by dividing the watts by 746 ; or the power absorbed by the brake 
can be reduced to watts as follows : — 

If the length, I, be given in centimeters, and the weight, w, be taken in 
grams, the power absorbed by the brake is measured directly in 
ergs, and as one watt = 10 7 ergs, the 

"Watts output at the brake r= J n „ — = W. 



The watts input = W„ and efficiency 



W 



io 7 



X 100. 



If the output is measured in I ■=. feet and w = lbs., then 

W=2.72irlw. 

W 
Input in h.p. = —£ = h.p. 

Output H.P. = 2 v j ^ W and 



efficiency^ = 100 



550 
H.P. 
h.p. 



MOTOR EFFICIENCY. 323 



If it is desired to know the friction and other losses in the motor, after the 
Drake test has been made, the brake can he removed, and the watts neces- 
sary to drive the motor at the same speed as when loaded, can be ascertained. 

[Electrical load test (including loss in belting, and extra loss in bear- 
ings due to pull of belt). — This test consists in belting a generator to the 
motor and measuring the electrical output of the generator, which added to 
the friction and other losses in the generator, makes up the load on the 
motor. The efficiency is then measured as before, by the ratio of output to 
input. The great advantage of this form of test is, that it can be carried on 
for any length of time without trouble from heat, and the extra loss in 
bearings due to pull of belt is included, which is therefore an actual com- 
mercial condition. 

In this form of test the losses in the generator are termed counter torque, 
and the method of determining them is given following this. 

Counter torque. — In tests of some motors, especially induction mo- 
tors, the load is supplied by belting the motor under test to a direct current 
generator having a capacity of output sufficient to supply all load, including 
overload. 

In determining the load applied to the motor and the counter torque, it is 
necessary to know, besides the /. E. or watts output of the generator, the 
following : — 

I 2 R of generator armature, 

Core loss of generator armature, 

Bearing and brush friction and windage of generator, 

Extra bearing friction due to belt tension. 

It is necessary to know the above items for all speeds at which the com- 
bination may have been run during the testing. This is especially useful 
in determining the breakdown point on induction and synchronous motors, 
both of which can be loaded to such a point that they " fall out of step." 

While the motor is under test especial note should be made of the speeds 
at which the motor armature and generator armature rotate, and of the 
watts necessary to drive the motor at the various speeds without load. 

The counter torque will then be the sum of the following three items : — 

W= I 2 R of generator armature, 
Wc = core ioss of generator armature, 
F = bearing and brush friction and windage of the generator armature. 

The field of the D. C. machine must be separately excited and kept at the 
same value during the load tests and the tests for*" stray power," and does 
not enter into any of these calculations. 

Belt-on test. — After disconnecting current from the motor under test, 
and with the belt or other connection still in place, supply sufficient volt- 
age to the D. C. machine armature to drive it as a motor at the speeds run 
during the motor test, holding the field excitation to the same value as before, 
but adjusting the voltage supplied to the armature for changing the speed. 

Take readings of 

Speed, i.e., number of revolutions of D. C. armature, 
Volts at D. C. armature, 
Amperes at D. C. armature. 

Construct a curve of the power required to drive the combination at the 
various speeds shown during the motor test. 

Belt-off test. — Throw the belt or other connection off, and take read- 
ings similar to those mentioned above, which will show the power necessary 
to drive the D. C. machine without belt. 

Then for any speed of the combination the '" stray poicer" will be found 
as follows : — 

W, = watts from belt-off curve, required fo drive the D. C. machine as 

a motor. 
W/y = watts from belt-on curve, required to drive the combination. 
Wc = core loss in D. C. armature. 
F=z friction of D. C. machine, belt off. 

F, — friction of motor under test, running light and without belt. 
/ -=z increase in bearing friction of D. C. machine, due to belt tension. 
f t = increase in bearing friction of motor, due to belt tension. 



324 



TESTS OF DYNAMOS AKD MOTORS. 



From the belt-off curve, 

W t — We + F. (1) 

From the belt-on curve, 

W„ = wo + F+F,+f +//• (2) 

Subtract (1) from (2) 

W„- W / = F / +f+f / 

W // -W / -F / =f+f / . (3) 

The values of / and f, cannot be determined accurately ; but if tbe ma- 
chines are of about the same size as to bearings and weights of moving 
parts, it is very close to call them of equal value, when, 

(W„— W,-F y ) 



/or// 



(4) 



The friction F / of the motor under test has been previously found by 
noting the watts necessary to drive it at the various speeds. If it is an in- 
duction motor, the impressed voltage is reduced very Ioav in determining 
the friction in order that the core loss may be approximately zero. 

As all the values of the quantities on the right-hand side of the equation (4) 
are now known,/ is determined, and may be added to W, to give the total 
" stray power.'''' A curve is then plotted from the values of " stray power " 
at different speeds. 

Counter torque = W, +/ +, 
Total load — I E + IHl + ( W, +/ ), 

Where I E =. watts load on the I). C. machine when it is being driven by 
, the motor, 

If S = Wt +/= " stray power" then 
Total load = 1. E. + I 2 B + 8. 

The value of / is so small when compared with the total load, that any 
ordinary error in its determination will cut no figure. 



Test of Street-Railway Motors. 

The " pumping -back " test, as described before, with some little modifica- 
tion serves for testing street-railway motors. The following diagram shows 
the arrangement and electrical connections. 

The motoi-s are driven mechanically by another motor, the input to which 
is a measure of the 

SHAFT 



SUPPLYING CORE 
LOSSES AND FRICTION 




BOOSTER SUFPLYING IR 



Fig. 14. 



losses, frictional, core 
losses, gears, bearings, 
etc., in the two motors ; 
the two motors are 
connected in series, 
through a booster, B, 
care being taken to 
make the connections 
in such a manner as to 
have the direction of 
rotation the same ; 
and their voltages op- 
posing. 
Readings are taken and the efficiencies are calculated as in the ' 

In eliminating the friction of bearings, etc., and of the driving-motor, it is 
run first without belts, the input being recorded as taken, at the speed 
necessary. The belt is then put on and a reading taken at proper speed, 
with both the motors under load. 

The load being adjusted by varying the field of booster B, the total losses 
of the system are then IE from booster plus the difference between belt-on 
reading Avith full load through the motors, and belt-off reading as noted 
(allowance being made for change of I 2 R of driving-motor). If the two 
motors are similar, half this value is the loss in one motor, from which the 
efficiency can be calculated as previously shown. 

Induction motors. — In addition to the tests to which the D. C. motor 



Diagram of connections and arrange- 
ment of street-railway motors. 

pumping- 



MOTOR EFFICIENCY. 



S2d 



is ordinarily submitted, there are several others usually applied to the in- 
duction motor, as follows : — 

Excitation; Stationary impedance ; Maximum output ; and some variations 
on the usual heat and efficiency tests. 

Excitation: This is also the test for core loss -f- friction, allowance being 
made for I 2 B of field ; with no belt on the pulley the motor is run at full 
impressed voltage. Read the amperes of current in each leg, and total 
watts input. The amperes give the excitatiou or " running-light" current, 
and the watts give core loss -4- friction -4- I' 2 R of excitation current. 

Stationary impedance : Block the rotor so it cannot move, and read volts 
and amperes in each leg, and total watts input; This is usually done at 
half voltage or less, and the current at full voltage is then computed by 
proportion. This then gives the current at instant of starting, and a meas- 
ure of impedance from which, knowing the resistance and core loss, other 
data can be calculated, such as maximum output, efficiency, etc. 

Maximum, output : This might be called & break-down test; as it merely 
consists in loading the motor to a point where the maximum torque point is 
passed and thus the motor comes to rest. 

Keep the impressed voltage constant and apply load, reading volts, am- 
peres in each leg, the total watts input, and revolutions ; also record the 
load applied at the time of taking the input. Then take counter torque as 
explained before, from which the efficiency, the apparent efficiency, the 
power factor, and maximum output are immediately calculated. 

Heat test. — Run motor at full load for a sufficient length of time to 
develop full temperature, then take temperatures by thermometer at the 
following points : — 

1 . Room, not nearer to the motor than three feet and on each side of motor. 

2. Surface of field laminations. 

3. Ducts (field). 

4. Field or stator conductors, through hole in shield. 

5. Surface of rotor. 

6. Rotor spider and laminations. 

7. Bearings, in oil. 

During heat run, read amperes and volts in each line. 

Efficiency test. — Apply load to the motor, starting with nothing but 
friction ; make readings at twelve or more intervals, from no load to break- 
down point. Keep the speed of A. C. generator constant, also the impressed 
voltage at the motor. 

Read, Speed of motor. 

Speed of A. C. dynamo. 

Amperes input to motor, in each leg. 

Volts impressed at motor terminals. 

Watts input to motor, by wattmeter. 

Current and volts output from D. C. machine belted to motor, 

Counter torque as explained above, and excitation reading watts. 

From the above the efficiency, apparent efficiency, power factor 
/ apparent efficiency \ 



real efficiency / 



and maximum output can be calculated. 



In reading watts in three-phase motors, it is best to use two wattmeters, 
connected as shown in following sketch : — 

1, 2, 3, are the three-phase lines leading to the 
motor. 

A and B are two wattmeters. 

b is the current coil of A, and b x of B. 

a is voltage coil of A, and a 1 of B. 

The sum of the deflections of A and B give total 
watts input. At light loads one Avattmeter usually 
reads negative, and the difference is the total watts. 

Results. — At the end of the preceding tests the 
following results should be computed, and curves 
plotted from them. 



1 


1 


> 3 








> o 




»' 



Fig. 15. 



, . Speed of motor x 100. 

synchronism = -i— — - — 

Synchronous speed. 



326 



TESTS OF DYNAMOS AND MOTORS. 



real efficiency 



apparent efficiency = 



Power factor = 



Output of motor x 100 
Input by wattmeter 

Output of motor x 100 



volt x amperes 
Watts 



Volt x amperes 
Torque-pounds pull at 1 ft. radius 



apparent efficiency 
real efficiency 

5,250 H.P. 
revolutions per minute 



The above results should be plotted on a sheet in curves similar to the fol- 
lowing, taken from Steinmetz's article on " Induction Motors." 




45 50 65 60 « 

<50^OVERL-OAD>! 



Fig. 16. Curves of results of tests of induction motor. 



Synchronous motor. — Synchronous motors are separately excited, 
and the D. C. exciter should have its qualities tested as a dynamo. Syn- 
chronous motors are tested for Break-down point ; Starting current at differ- 
ent points of location of the rotor ; Least exciting current for various loads. 
All these in addition to the regular efficiency and other tests. Core losses, 
friction, T^R losses, etc.*, can be found by any of the usual methods pre- 
viously described. 

Break-down point. Synchronous motors have but little starting-torque ; 
and it is necessary to start them without load, throwing it on gradually 
after the motor has settled steadilv and without "hunting" on its synchro- 
nous speed. The break-down point is found by applying load to the point 
where the motor falls out of step, which will be indicated by a violent rush 
of current in the ammeter simultaneous with the slowing down. 

This test is usually carried out at about half voltage, the ratio of the load 
on the motor at the "moment of dropping out of step will be to the full load 
of break-down as the square of the voltages, the load being adjusted at 
minimum input in each case. For example, say a certain motor, built to 
run at 2,000 volts, breaks down at 150 K.W., with an impressed voltage of 
1,000. Then the true full break-down load will be 



2,000 2 
1,000 2 



X 150 = 600 K.W. 



SYNCHRONOUS MOTOR. 327 



Starting current. Owing to consequent disturbance to the line, it is desi- 
rable tbat the starting current of a synchronous motor be cut down to the 
lowest point ; but it is difficult to reduce this starting current lower than 
200% of full-load current. A synchronous motor also starts easier at certain 
positions of its rotor as related to poles. With the rotor at rest, and the 
location of the centre of its pole-pieces chalked on the opposite member, 
the circuit is closed, the impressed voltage is kept constant, and the current 
flowing in each leg of the circuit is read, and the time to reach synchro- 
nism. Care should be taken to note the amount of the first rush of current, 
and then the settling current at speed. 

Least exciting current. The power factor of a synchronous motor will be 
100 only when, with a given load on the motor, the exciting current is ad- 
justed so that there is neither a leading nor lagging current in the armature. 
Sometimes it is desirable to produce a leading current in order to balance 
the effect of induction motors on the line, or inductance of the line itself. 
This is done by over-exciting the fields. 

With a given load on the motor, the 100 power-factor is found by com- 
paring the amperes in the motor armature with the exciting current in the 
field. Starting with the excitation rather low, the armature current will be 
high' and lagging ; as the excitation is increased, the armature current will 
drop, until it reaches a point where, as the excitation is still increased, the 
armature current begins to rise, and keeps on rising as the exciting current 
is increased, and on this side of the low point the armature current is 
leading. 

With no reason for making a leading current, the best point to run the 
motor at is, of course, that at which the armature current is the lowest ; and 
at that point the power-factor is 100. 

Synchronous Impedance. — The E.M.F. of an alternating dynamo 
is the resultant of two factors, i.e., the energy E.M.F. and inductive E.M.F. 

The energy E.M.F. may be determined from the saturation curve by run- 
ning the machine without load, and learning the field strength necessary to 
produce full voltage. 

The inductive E.M.F. is at right angles to the energy E.M.F., and is de- 
termined by driving the machine at speed, short-circuiting the armature 
through an ammeter, and exciting the field just enough to produce full-load 
current in the armature. The amount of field current necessary to produce 
full load is a measure of the inductive E.M.F., which can be determined from 
the saturation curve as before, and the resultant E.M.F. will be 

Resultant E.M.F. = Venergy E.M.F. 2 + inductive E.M.F. 2 . 

Saturation test. — This test shows the quality of the magnetic cir- 
cuit of a dynamo, and especially the amount of current necessary to saturate 
the field cores and yokes to a proper intensity. In this test it is important 
that the brushes and commutator be in good condition, and that all contacts 
and joints be mechanically and electrically tight. 

The dynamo armature must be driven at a constant speed, and the leads 
from the voltmeter placed to get readings from the brushes of the dynamo 
must have the best of contacts. 

The fields of the dynamo must be separately excited, and must have in 
the circuit with them an ammeter and rheostat capable of adjusting the 
field current for rather small changes of charge. 

The armature must be without load, and a voltmeter must be connected 
across its terminals. 

Should there be residual magnetism enough in the iron to produce any 
pressure without supplying any exciting current, such pressure should be 
recorded ; or perhaps a better "way is to start at zero voltage by entirely 
demagnetizing the fields by momentary reversal of the exciting current. 

To start the test, read the pressure, due to residual magnetism if not de- 
magnetized, or if demagnetized, start at zero. Give the fields a small ex- 
citing current, and read the voltage at the armature terminals ; at the same 
time read the current in the fields, and the revolutions of the armature. 
Increase the excitation in small steps until the figures show that the knee of 
the iron curve has been passed by several points ; then reverse the operation, 
decreasing the excitation by like amounts of current, until zero potential is 
reached. 

This is iisually as far as it is necessary to go in practice ; but occasionally 



3:>8 



TESTS OF DYNAMOS AND MOTORS. 



it is well to complete the entire magnetic cycle by reversing the exciting cur- 
rent, and repeating the steps and readings as above described. 

The readings should be plotted in a curve with the amperes of exciting 
current as abscissae, and volts pressure as ordinates. 

The E.M.F. will be found to increase rapidly at first ; and this increase 
will be nearly proportional to the exciting current until the " knee " in the 
curve is reached, when the E.M.F. increase will not be proportional to the 
excitation until after the "knee" is passed, when the increase in E.M.F. 
will again become nearly proportional to the excitation, but the increase 
will be at such a low rate as to show that the magnetic circuit is practically 
saturated ; and it is not economical to work the iron of a magnetic circuit too 
far above the knee, nor is it expedient to work it at a point much below the 
" knee," except for boosters. 

The exciting current mixst not be broken during this test, except possibly 
at zero ; nor must its value be reduced or receded from in case a step should 
be made longer than intended. Inequalities of interval in steps of excit- 
ing current will make little difference when all are plotted on a curve. For 
the same value of exciting current the down readings of E.M.F. will always 
be higher than those on the up curve. 

Resistance of field coils. — The resistance of the shunt fields of a 
dynamo or motor can be taken in any of the usual ways : by Wheatstone 
bridge ; by the current flowing and drop of potential across the field termi- 
nals ; and it is usual, in addition, to take the drop across the rheostat at the 
same time. The resistance of each field coil should be taken to insure that 
all are alike. 

Resistance of series fields, and shunts to the same, must be taken by a dif- 
ferent method, as the resistance is so low that the condition of contacts may 
vary the results more than the entire resistance required. The test for re- 
sistance of armatures following this is quite applicable. Of course any test 
for low resistances is applicable ; but the one described is as simple as any, 
and quite accurate enough for the purpose. 

Resistance of armature. — In order to determine the I Hi loss in a 
generator or motor armature, its resistance must be measured with consider- 
able care ; and the ordinary Wheatstone bridge method is of no use, for the 
reason that the variable resistance of the contacts is often more than that 
of the armature itself. The drop 
method, so useful with higher re- 
sistance devices, is not accurate 
enough for the work ; and the 
most accurate method is probably 
the direct comparison -with a stan- 
dard resistance by means of a 
good galvanometer and a storage 
battery. 

Clean the brushes, commutator 
surface, or surface of the col- 
lector-rings, and in the case of a 
D. C. machine, see that opposite 
brushes bear on opposite seg- 
ments. 







Fig. 17. Diagram of arrangement for 
measuring resistance of armatures. 



Connect the galvanometer and its leads, the storage battery and resis- 
tances, as in the following diagram. The standard resistance, R, will ordina- 
rily be about .01 ohm, but may be made of any size to suit the circumstances. 
The storage battery must be large enough to furnish practically constant 
current during the time of testing. The galvanometer must be able to 
stand the potentials from the battery ; and it is usually better to connect in 
series with it a high resistance, so that its deflections may not be too high. 
The deflection of the galvanometer should be as large as possible, and pro- 
portional to the current flowing. The leads a, «,, and b and 6,, are so ar- 
ranged with the transfer switch that one pair after the other can be thrown 
in circuit with the galvanometer ; and it is always well to take a deflection 
first with R, then again after taking a deflection from the armature. 

The leads a and « x must be pressed on the commutator directly at the 
brush contacts, and may often be kept in place by one of a set of brushes 

Xest. — Close the switch, k, and adjust the resistance, r, until the am- 
meter shows the amount of current desired, and watch it long enough to be 



ARMATURE FAULTS. 



320 



sure it is constant. Close the transfer switch on b and b lt and read the gal- 
vanometer deflection, calling it d. Throw the transfer switch to the con- 
tacts a, anda,, read the galvanometer deflection, and call it d v Transfer 
the contacts back to b, and b t and take another reading ; and if it differs 
from cf lt take the mean of the two. 

Let x = resistance of the armature, then 

d 

Note. — See Flemming's " Electrical Laboratory Notes and Forms." 




m 

AM. ' M-K. 

STORAGE .BATTERY 

Fig. 18. Test for break in 
mature lead. 



Tests for faults in Armatures. 

The arrangement of galvanometer for testing the resistance of an arma- 
ture is the very best for searching for faults in the same, although it is not 
often necessary to measure resistance. 

Test for open circuit. — Clean the brushes and commutator, then 
apply current from some outside source, say a few cells of storage battery 
or low pressure dynamo, through an am- 
meter as in the following diagrams. Note 
the current indicated in the ammeter ; ro- 
tate the armature slowly by hand, and if the 
break is in a lead, the flow of current will 
stop when one brush bears on the segment 
in fault. Note that the brushes must not 
cover more than a single segment. 

If on rotating the armature completely 
around the deflection of the ammeter does 
not indicate a broken lead, then touch the ter- 
r _ minals of the galvanometer to two adjacent 
" bars, working from bar to bar. The deflec- 
tion between any two commutator bars 
should be substantially the same in a perfect armature ; if the deflection 
suddenly rises between two bars it is indicative of a high resistance in the 
coil or a break (open circuit). 

The following diagram shows the connec- 
tions. 

A telephone receiver may be used in place 
of the galvanometer, and the presence of 
current will be indicated by a " tick " in the 
instrument as circuit is made or broken. 

Test for short circuit. — Where two 
adjacent commutator bars are in contact, or 
a coil between two segments becomes short- 
circuited, the bar to bar test with galvanom- 
eter Avill detect the fault by showing no 
deflection. If a telephone is used, it will be 
silent when its terminal leads are connected 
with the two segments in contact. See dia- 
gram below for connections. If there be a short circuit between two coils 

the galvanometer terminals 
should include or straddle three 
commutator bars. The normal 
deflection will then be twice that 
indicated between two segments 
until the coils in fault are 
reached, when the deflection will 
drop. When this happens, test 
each coil for trouble ; and if indi- 
vidually they are all right, the 
trouble is between the two. The 
following diagram shows the con- 
nections. 

Test for grounded arma- 
ture. — Place one terminal of the 
galvanometer on the shaft or 
frame of the machine, and the other terminal on the commutator. (The 




HIGH 

Fig. 19. Bar to bar test for 
open circuit in coil. 




SHORT CIRCUIT 

BETWEEN SEGMENTS 

OR IN COIL 



SHUNT 



Fig. 20. Bar to bar test for short cir- 
cuit in one coil or between commuta- 
tator segments. 



330 



TESTS OF DYNAMOS AND MOTORS. 




SHORr*CIR"C'0]f 
BETWEEN SECTIOBB 



Fig. 21. Alternate bar test for short 
circuit between sections. 



storage battery, ammeter, and leads must be thoroughly insulated from 

ground.) If, under these circumstances, there is any deflection of the gal- 
vanometer, it indicates the presence 

of a ground, or contact between the 

armature conductors and the frame 

of the machine. Move the terminal 

about the commutator until the least 

deflection is shown, and at or near 

that point will be found the contact 

in the particular coil connected be- 
tween two segments showing equal 

deflection, unless the contact happens 

to be close to one segment, in which 

case there will be zero deflection. 

Contacts in field coils can be located 

by the same method. The following 

diagram shows the connections. 
To determine if armature of multipolar dynamo is electrically centred, put 

down brushes 1 and 2, and take volt- 
age of machine ; put down brush 3, 
and lift 1, take voltage again ; put 
down brush 4 and lift 2, again tak- 
ing voltage ; repeat the operation 
with all the brushes, and the volt- 
age with any pair should be the 
same as that of any other pair if the 
armature is electrically central. 

The same thing can also be deter- 
mined by taking the pressure curves 
all around the commutator as shown 
in the notes on characteristics on 
dynamos. 



GROUNDED TO 001 
AT THUS PQ\hV 




Test for ground in armature 
coils. 



In the above the brushes should be exactly at the neutral point. 



Test for E.OT. i\ of Dynamo without Running- it. 

Prof. F. B. Crocker gives the following method (page 247 Trans. A. I. E. E., 
1897), for determining the E.M.F. of a dynamo without driving it by outside 
power, provided a current of the proper voltage is at hand sufficient to give 
it full torque as a motor. 

Clamp a lever to the pulley, and weigh the torque, as a motor, at radius r, 
with a spring balance or a platform scale. 

r rz radius of torque lever. 

s = speed of revolutions per minute, as a dynamo. 
p = pounds pull at radius r. 

1= current. 
E = E.M.F. 

E I _ 2nr sp 
746 — 33,000 ' 

Field strength is the same as if running as a dynamo ; and by tapping 
the shaft when test is made, friction losses are partially eliminated, and the 
method is sufficiently correct for all efficiencies. 



THE STATIC TRANSFORMER. 

The static transformer is a device used for changing the voltage and cur- 
rent of an alternating circuit in pressure and amount. It consists, essen- 
tially, of a pair of mutually inductive circuits, called the primary and 
secondary coils, and a magnetic circuit interlinked with both the primary 
and secondary coils. This magnetic circuit is called the core of the trans- 
former. 

The primary and secondary coils are so placed that the mutual induction 
between them is very great. Upon applying an alternating voltage to the 
primary coil an alternating flux is set up in the iron core, and this alternat- 
ing flux induces an E.M.F. in the secondary coil in direct proportion to the 
ratio of the number of turns of the primary and secondary. 

Technically, the primary is the coil upon which the E.M.F. from the line 
or source of supply is impressed, and the secondary is the coil within which 
an induced E.M.F. is generated. 

The magnetic circuit or core in transformers is composed of laminated 
sheet iron or steel. The following cuts represent sections of several dif- 
ferent types. 



r 


> 




4 f- 




1.3 


V 


_> 



P V P. 



■'■■ 



TJ 







p" 








I 

i 




1 



I i 


— 


i | 




P f 




Is! pj 


_i 


! 




! ! 



pjs 




i... 









Sjpj 


1 




— I 


p j i 




v>A ■ 


1 


S.PJpiE 

1 l ! 


















1 













i 

PIE 
1 






; 

S P 








! 





FlG. 1. Cores of some American Transformers. 
p = primary winding ; s = secondary winding. 

In those showing a double magnetic circuit the iron is built up through 
and around the coils, and they are usually called the " Shell " type of trans- 
former. 

331 



B82 THE STATIC TRANSFORMER. 



Those having a single magnetic circuit, and having the coils built around 
the long portions or legs of the core, the short portions or yoke connecting 
these legs at each end, are called " core " type of transformer. 

The duties of a perfect transformer are : 

(1) To absorb a certain amount of electrical energy at a given voltage and 
frequency, and to give out the same amount of energy at the same frequency 
and any desired voltage. 

(2) To keep the primary and secondary coils completely isolated from one 
another electrically. 

(3) To maintain the same ratio between impressed and delivered voltage 
at all loads. 

The commercial transformer, however, is not a perfect converter of energy, 
although it probably approaches nearer perfection than any form of appa- 
ratus used to transform energy. The difference between the energy taken 
into the transformer and that given out is the sum of its losses. These 
losses are made up of the copper loss and the core loss. 

The core loss is that energy which is absorbed by the transformer when 
the secondary circuit is open, and is the sum of the hysteresis and eddy cur- 
rent loss in the core, and a slight copper loss in the primary coil, which is 
generally neglected in the measurements. 

The hysteresis loss is caused by the reversals of the magnetism in the 
iron core, and differs with different qualities of iron With a given quality 
of iron, this loss varies as the 1.6 power of the voltage with constant fre- 
quency. 

Steinmetz gives a law or equation for hysteresis as follows : 

Wh = v (B l -°- 

Wa = Hysteresis loss per cubic centimeter per cycle, in ergs (=: 10~ 7 
'joules). 
r] = constant dependent on the quality of iron. 

If 2f = the frequency, 

V— the volume of the iron in the core in cubic centimeters, 
P = the power in watts consumed in the whole core, 

then P — v NV(^- G lQ-\ 

T> 

and 7) = 



n rru 1 - 6 10- 7 



In Table A, on page 333, this hysteresis constant rj is given for several 
different transformers. 
In the construction, the core loss depends on the following factors : 

(1) Magnetic density, 

(2) Weight of iron core, 

(3) Frequency, 

(4) Quality of iron, 

(5) Thickness of iron, 

(6) Insulation between the sheets or laminations. 

The density and frequency being predetermined the weight or amount of 
iron is a matter of design. The quality of the iron is very variable, and up to 
the present time no method has been found to manufacture iron for trans- 
formers which gives as great a uniformity of results as to the magnetic 
losses as could be desired. 

On the thickness of the laminations and the insulation between them de- 
pend the eddy current losses in the iron. Theoretically 1 the best thickness 
of iron for minimum combined eddy and hysteresis loss at commercial fre- 
quencies is from .010" to .015", and common practice is to use iron about 
.014" thick. 

The copper losses in a transformer are the sum of the I 2 Ii losses of both 
the primary and secondary coils, and the eddy current loss in the conductors. 
In any well-designed transformer, however, the eddy current loss in the 
conductors is negligible, so that the sum of the I 2 E losses of primary and 
secondary can be taken as the actual copper loss in the transformer. 

i Bedell, Klein, Thomson, Elec. W., Dec. 31. 1898. 



TABLE A. 



333 



V- 



e3 


s 


o 














II 


X 


















CO 

© 




O 
OS 


>* O t> CM CM <* 

O i-l lO H CM CM 


© 00 
© CM 


§ 


© CO 
CM CO 


o 
O 

"3 


CM 




CM 


CO CM CO <M CM CM 


CM CM 


CM 


CM © 


id 

<M 
li 


o 
X 

3 






M O O •* CO Tti 
lO CO M N « lO 


CM lO 


3 


00 CO 
00 t- 








M 




eo 


CO <N © CM CM CM 


CM CM 


rt 


CM rt* 






© 

© 
II 


p 

00 




8 

01 


5400 

7500 
7720 
7560 
4080 

4960 


1 1 
CO © 


© 

1 


© © 
t- © 

t- © 


6 






































1C 




















fl 


o 




o 


o o o o o . o 

© tH lO CO CO 00 

CO CO t- CO O CO 
CM CO CO CO rH CM 


© © 

© CM 

■* CO 


1 


© © 

CO CO 






8 


q 


lO 

© 














5 


II 

^5 


p 


tH '" <N SO ' CM © CO i-H 

© © © © © © © 


8 S 


q 8 


q § 




5 




































CD 
CM 


1 
II 


p 


p 


p 


CO lfl H ij lO rf 00 

p p © p p p © 


CO <* 

© p 


■* CO 

q q 


q q 






o 
© 

II 


















6 


K0 


CM 


CO 


^§ 2 1? -1 S S 


5 % 


Tf © 
CO TtJ 


T*< t- 

eo t-. 


















j» 




4 
















K? 


II 


CM 


oo 


CO 


S S 8 Sj 3 • 3 S 


s §* 


"# © 
CM CM 


© © 
CM r)< 






^ 




















s 
II 


© 


s 


3 


© LO CO IS CM CM t> 

© CM Ci CM "# 00 © 


CI © 
CO © 


l-H © 

CM lO 


CM t~ 




-73 

O 

Ph 








i-l i-l CO »-l T-l 






i-l CM 




















CD 


lO 


















Ph 


II 


CD 
OS 


cm 

o 


CO 


\o m -# ia cm cm oo 

t~ CO i-l CO CO -* -cH 


i>- CM 

© 00 


3 b2 


CO CO 












CM i-l 










d 




- 


(M 


CO 


■* ia © t- oo cs © 


!H CM 


CO Th 





334 



THE STATIC TRANSFORMER. 



TRANSFORMER K«*X J.tTIOXft. 

Practically all successful designs of transformers are determined to 
greater or less extent by the method of cut and try. Empirical methods 
are of little value if the designer can obtain data on other successful trans- 
formers for the same kind of work, and base the calculations for the new 
apparatus on the behavior of the old while under test. 

For any transformer or reactive coil : 

Let E — Vmean 2 of the induced E.M.F. 
$ = total flux, 
(jy = lines of force per square inch. 
A = section of magnetic circuit in square inches. 
A T = frequency in cycles per second. 
T= total turns of wire in series. 

2tt 



4 - 44 =V^ = V 2Xir 



Then E = 



4.44 A^T 
10 s 



(1) 



This equation is based.on the assumption of a sine wave of electromotive 
force, and is the most important of the formulae used in the design of an 
alternating current transformer. 

By substituting and transposing we can derive an equation for any \\n- 
known quantity. 

Thus if the volts, frequency, and turns are known, then — 



$ = 



But $ 



Therefore A = 



Ex 10 8 

4.44xlxT 



Ex 10 8 
4.44 xtfxTx 



(2) 
(3) 
(4) 



which equation gives at once the cros^ section of iron necessary for the 
magnetic circuit after we have decided on the total primary turns, and the 
density at which it is desired to work the iron. 

Again, if the volts, frequency, cross section of core, and density are 
known, we have, transposing equation (4), 



T = 



E X 10 8 



4.44xA r X(ft // X^ 



1.J3 
1.4 
1.2 
1.0 

.8 



'"""■ 




1 


















"s .. : Zzi 




-w „- 


i- ,' 




X ' 


-S *- 






St ^ 










"I ~ ~ ~ __ 






J- - ~~ 


I: - 







12 1' 

Fig. 2. 



16 18 20 22 



THE STATIC TRANSFORMER. 335 



Fig. 2 is a curve giving the total fluxes as ordinates and capacities in k.w. 
as abscissae. This curve represents approximately common practice for a 
line of lighting transformers, to be operated at 60 cycles. 

For any other frequency or for power work, a curve of total fluxes can be 
drawn after three or more transformers have been calculated with quite 
widely differing capacities. 

Iflag-netic densities in the cores of transformers vary considerably 
with the different frequencies and different designs of various makers. The 
practical limits of these densities are as follows : 

For 25 cycle transformer from 60,000 to 90,000 O.G.S. lines per square inch. 

For 60 cycle transformers from 40,000 to 60,000 lines per square inch. 

For 125 cycles from 30,000 to 50,000 lines per square inch. 

Densities for other frequencies are taken in proportion. 

Current densities in transformer windings vary between 1000 and 
2000 circular mills per ampere. Some makers design for greater current 
density in the secondary than in the primary. The circular mils per am- 
pere in transformers of the best design are often 1000 or 1500 in the primary 
coil, and 1200 or 2000 for the secondary coil. 

The proper adjustment of the current density should be such as to give 
equal heat distribution throughout the coils, and the relative densities in 
the two coils should be based on their relative radiating surfaces. 

FEATURI!§ OF DESIGlf. 

In the design of a successful transformer, the features to be given partic- 
ular attention are : 

(1) Insulation between primary and secondary, 

(2) Heating, 

(3) Efficiencies, 

(4) Regulation, 

(5) Cost, 

(6) Power factor and exciting current. 

Insulation. 

The insulation of a transformer is really a measure of its durability, and 
it must be obvious that if it is not well designed and properly constructed 
to prevent the breakdown of its insulation, it is not a good investment ; and 
the same reasoning holds good if the insulation deteriorates rapidly. Sim- 
plicity of form and constructive details is a good point, and as transformers 
are liable to be exposed to all sorts of weather and other conditions, they 
should always be designed to withstand all of them. 

Insulation between coils must be of the best possible kind, as electrical 
connection here is a menace to life and property, and destruction of the 
transformer also means costly repairs, loss of income while current is off, 
and what is of more importance, great annoyance to customers. 

A liberal margin of overload is necessary, and if specifications call for a 
rise of temperature not exceeding 40° C, at full load, any ordinary overload 
will do no harm, provided the insulation is safe. The rules of the Committee 
on Standardization of the A. I. E. E. state the proper voltages to be used in 
testing transformers for insulation, and the values so stated will be found in 
the part of this chapter devoted to tests of transformers. The writer has 
never been thoroughly satisfied with the methods in common use for deter- 
mining the rise of temperature in transformers or dynamos Or similar appli- 
ances. The thermometer test is too superficial, and the resistance test is 
the average only, while what is wanted is the hottest temperature at any 
point, for that is the danger point. It is probable that the ordinary small 
commercial sizes of transformers do not need such refinements, but the 
larger sizes would be much better tested with a special copper test coil 
placed at the danger point during construction, with leads brought outside 
for testing. This might not be necessary in more than one or two of the 
same type and size, but would never be out of place in every one of the 
larger sizes now coming so commonly into use in the modern power trans- 
mission plant. Insulation materials for transformers are Of numerous 
kinds, and no two makers use identical combinations, although most use 
the same or similar materials ; following is a list of those in common use ; 



386 



FEATURES OF DESIGN. 



and the reader is referred to the list of specific resistances (see index) for the 
breakdown point of most of them. 

Oiled linen, 

Oiled silk, 

Mica, 

Micanite, flakes of mica pasted together in different forms, 

Fiber, and all the other forms of artificial board. 

Wires are nearly always double cotton covered. 

As for oils for the oil-insulated transformers, the Westinghouse Company 
uses a clear thin oil much like signal-oil, and called Red Seal,_ while the Gen- 
eral Electric Company uses a special transformer oil, which is heavy, but is 
simply a good machine-oil freed from water. 

An order to the Standard Oil Company for transformer oil will bring an 
oil that will serve every ordinary purpose, and many times it will be found 
that unless some particular oil is specified they will seldom send the same 
twice. The laboratory of the National Board of Fire Underwriters has used 
a number of different kinds in its high-testing transformers (40,000 volts), 
and has never found any difference in results although ordered as stated 
above. 

Heating- and Ventilation. 

One of the necessary requirements of any piece of machinery is that 
it must be able to operate for certain periods of time at its full load, and in 
some cases over-load, without undue heating. 




Fig. 3. G. E. Co. Type H Transformer — 20000 watts, oil-cooled. 

In a transformer, the capacity for work increases directly as the volume 
of material, densities and proportions remaining constant. The volume, 
however, increases as the cube of the dimensions, and the radiating surface 
as the square of the dimensions ; therefore, it is evident that the capacity 
for work increases faster than the radiating surface. Since the losses are 
also in proportion to the volume, the designer soon reaches a point where it 
is necessary to provide additional means for ventilation or radiation of heat, 
in order that the transformer may run under load without undue tempera- 
ture rise. 

Self-cooled transformers are those which require no artificial means for 



THE STATIC TRANSFORMER. 



337 



dissipating the heat energy lost in the apparatus during operation. These 
can be divided into two classes, the Ventilated or Natural Draft, and the 
oil-cooled. 




Fig. 4.— 500-k.w. Self-Cooling Transformer. W. E. & M. Co. Type, Oil-cooled. 

The Ventilated or Natural Draft transformer is one in which 
air is the direct means of absorbing the heat, it being designed so that cur- 
rents of air readily pass through the transformer. Such transformers are not 
well adapted for out-door installations, as they require a separate housing; 
otherwise there is a liability of water or moisture getting inside of tbe case. 

Oil-cooled transformers are those in which the coils and core are 
immersed in oil, the oil acting as a medium to conduct the heat from the coils 
to the surrounding tank. In addition to acting as a heat-conducting medium, 
the oil also serves to preserve the insulation from oxidation, increases the 
breakdown resistance of the insulation, and re-insulates the insulation in 
case of a puncture. 

The use of oil in a transformer results in a more rapid conduction between 
the transformer proper and its case or tank, and the lowering of the tem- 
perature increases the life of the transformer. Again, instances are known 
of the discharge of " atmospheric electricity," or a discharge of lightning at 
a distance that has punctured the insulation of a transformer, and when filled 
with oil, the oil flows in and repairs the rupture, which may be too small to 
cause immediate damage. If a sufficient space is left inside' the case, the oil 
will get up a circulation by its own convection currents, the cooler oil rising 
inside as it becomes more and more heated, the hot oil on the top falling 
as it is cooled by contact with the inside surface of the tank. 

This cooling may be further increased by making the containing case with 
deep vertical corrugations, thus largely increasing its radiating surface. 

The curves on page 338 serve to show the effect on the temperature of the 
use of oil. Curve 1 represents the temperature rise (by resistance method) 
of a transformer without oil ; curve 2, the temperature rise of the same 
transformer with oil ; curve 3, the temperature rise of the oil ; curve 4, the 
temperature rise of another transformer run without oil ; and curve 5, the 
highest temperature rise accessible to thermometer, whose actual tempera- 
ture (by resistance) is shown in curve 4. 

When the transformers are of such a size that sufficient radiating surface 
cannot be had in the tank to dissipate the heat, it becomes necessary to 
provide artificial means for cooling the same. Some of the means adopted 
are, water circulation, forced oil or air circulation. For both the water and 
oil circulation the coils and core are immersed in oil. 

The water-cooled transformer has its heatad oil cooled by means 
of water circulating pipes placed in the oil. The transformer thus has the ad- 
vantage of oil insulation, and the circulation of the cold water through the 
pipes requires much less power than the pumping of the oil, and in addition 
does not require external cooling apparatus. This method is subject to a 
slight danger, due to possible leak of water pipes. 



33* 



FEATURES OF DESIGN, 



Transformers have been constructed in sizes up to about 2000 k.w., using 
water circulation for cooling. 

























































































100 


































































































































































- "" 






90 






































































"" 


































































































80 


















































, 












































































pM^. 


" 








































70 










































































































































































60 
















































































































S 




















z\- 


PS 


E 


i 








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— 


















50 




















































































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CURVE 


» 
















40 














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RVE 


3 






















30 












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- 
























20 
















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S 


s. 










































































10 




/ 
















































































r 








































































































































































TIME IN HOURS 
CURVES SHOWING RESULTS DUE TO USE OF OIL IN TRANSFORMERS- 



Fig. 5. 



Am Air-Blast Transformer — or one in which ventilation and radi- 
ation of heat is, by means of a blast or current of air, forced through the 
transformer coils and core is shown in Fig. 8. In this transformer, the 





Figs. 6 and 7. Natural Draft Transformer — Showing Case Removed. 

coils are built up high and thin, and assembled with spaces between them, 
the air being forced through these spaces. The iron core is also built up 
of numerous openings through which the air is forced for cooling pur- 
poses. This style of transformer has been constructed in sizes up to about 
1000 k.w. 



THE STATIC TRANSFORMER. 



839 



The following tables show results of tests on a number of commercial 
transformers by Mr. A. H. Ford. 




Fig. 8. Air-Blast Transformer. 

JB Heating- Teste. 

Transformers in their cases. (Ford.) 





Rise 


Watts ra- 
diated per 
sq. in. of 
Case. 


Watts ra- 
diated 




Rise 


Watts ra- 
diated per 


Watts ra- 
diated 


No. 


in 
Tempera- 


per sq. in. 
of Core 


No. 


in 

Tempera- 


sq. in. of 
Case. 


per sq. in. 
of Core 




ture °C. 


and Coils. 

w 2 . 




ture °C. 


and Coils. 

w 2 . 


1 


31.4 


.143 


.175 


9 


31.0 


.172 


.300 




24.3 


.091 


.107 




39.4 


.134 


.234 




57.4 


.168 


.198 










2 


20.1 


.052 


.110 


12 


31.6 


.086 


.145 




15.2 


.047 


.098 




20.5 


.067 


.113 




47.8 


.102 


.214 




51.8 


.125 


.211 




30.8 


.085 


.190 




21.5 


.122 


.206 


3 


20.8 


.105 


.121 


13 


60.0 


.113 


.131 




17.5 


.080 


.093 




49.4 


.079 


.104 




50.2 


.168 


.195 












38.4 


.134 


.155 










5 


21.8 


.118 


M& 


14 


43.4 


.168 


.266 




19.1 


.090 


.127 




32.1 


.079 


.130 




40.8 


.172 


.242 




101.8 


.250 


.396 




40.6 


.144 


.203 




76.9 


.150 


.234 


6 


62.4 


.388 


.542 


15 


25.4 


.099 


.150 




52.3 


.246 


.346 




21.2 


.074 


.112 




86.8 


.412 


.580 




67.5 


.168 


.255 




72.2 


.455 


.640 




51.6 


.149 


.225 


7 


20.0 


.082 




16 


73.4 


.225 


.396 




17.8 


.058 






66.1 


.175 


.242 




56.3 


.144 






100.0 


.340 


!466 




36.0 


.100 






70.0 


.242 


.334 



840 



THE STATIC TRANSFORMER. 



C ■Keating' Tests. 

Transformers out of their cases. 

(Ford.) 







Watts 






Watts 




Rise in 


radiated per 




Rise in 


radiated per 


No. 


Temperature 


sq. in. 
of Exposed 


No. 


Temperature 

°C. 


sq. in. 
of Exposed 




Surface. 




Surface. 






W. 






W. 


1 


27.9 


.175 


11 


27.0 


.274 




21.2 


.107 




18.9 


.208 




51.0 


.222 




52.2 
50.4 


.372 
.320 


2 


14.6 
13.6 


.110 
.098 










41.4 


.240 


12 


19.7 


.145 




42.4 


.220 




12.3 
55.9 


.113 

.229 


3 


20.3 
12.4 
33.2 


.122 
.093 
.167 




53.8 


.195 




30.8 


.136 


14 


29.1 
24.0 


.266 
.125 


4 


16.2 


.160 




96.7 


.382 




13.4 


.110 




77.0 


.286 




59.4 


.240 










51.4 


.200 














15 


25.1 


.150 


6 


50.0 


.547 




14.3 


.112 




24.4 


.346 




61.3 


.270 




72.0 


.595 




59.4 


.250 




58.9 


.655 








7 


14.0 


.082 


16 


44.3 


.396 




6.4 


.058 




31.4 


.243 




75.0 


.185 




64.3 


.438 




19.0 


.121 




42.9 


.304 



Efficiencies. 

The efficiency of a transformer is the ratio of the output watts to the input 
watts. Thus 



Efficiency 



Output watts _ 
Input watts output -\- core loss + copper loss 



Output 



The core loss, which is made up of the hysteresis loss and eddy current 
loss, remains constant in a constant potential transformer at all loads, while 
the copper loss, or I 2 R loss, varies as the square of the current in the pri- 
mary and secondary. Methods for determining all the losses are fully 
described in the chapter on transformer testing. 

In a service where a transformer is generally worked at full load, while 
connected to the circuit, as in power work, tlie average or " all-day" effi- 
ciency will be about the same as its full-load efficiency. By " all-day" effi- 
ciency is meant the percentage Avhich the energy used by the customer is of 
the total energy sent into the transformer during twenty-four hours. 

In lighting work the transformers are usually connected to the mains or 
are excited the full twenty-four hours per day, Avhile the customer draws 
current from them during' from three to five hours in the twenty-four. As- 
suming on an average five hours full load, the losses will be 5 hours I-Ii and 



FEATURES OF DESIGN, 



141 



24 hours core loss. The calculation of the " all-day " efficiency can, there- 
fore, be made by. the following formula : 

A11 , «, . Full load X 5 

All-day efficiency = Core loss x <24 + /2ig x 5 + Full load x 5 

From this it is evident that while for power work or continuous full load, 
the relative amount of the core and copper losses will not affect the " all- 
day" efficiency seriously, yet in the design of transformers which are 
worked at full load only a short time, but are always kept excited, a large 
core loss means a very low " all-day " efficiency. 

The two tables on pages 342 and 343 show various efficiencies of a number 
of transformers, giving maximum efficiencies and "all-day" efficiencies. 
They also show the core loss of various commercial transformers as found 
by Mr. Ford. 









I I II I I I I I I I I I I I I I 




















= 


A 
-B 

C 


TRANSFORMER IRON.AGEING TESTS. 

BY H. F. PARSHALL 
HYSTERESIS IN THE IRON AS RECEIVE: 
HYSTERESIS TRANSFORMER AFTER 

SHORT PERIOD OF LIGHT WORK 

HYSTERESIS TRANSFORMER AFTER 

THREE YEARS OF HEAVY WORK 














































/ 
















/ 
















/ 


















/ 




























































































































1S000 








































































































































































































































12000 






























c 












































































/ 
























































/ 
































































































/ 














/ 










































/ 














/ 










































/ 












/ 












































/ 




















A. 
















4000 


















/ 














































































































S 






^ 


















I I 




































































































































( 








I 






















i 








1 









1 


2 






4) 



LINES PFR SQUARE CENTIMETER 

Fig. 9. 



100 




































































































































































- 
















































































































































































































































































































































































































































































































































































c 


































































z 


































































- 


































































g™ 




















































































































CO 

1- 










/ 
























/ 












MANUFACTURE BY A.H. FORD, AT UNIVERSITY 

OF WISCONSIN. JAN. FEB. MAR. 1897. 

B- TEST ON WAGNER TRANSFORMER, 

FEB. MAR. APR. 1897. 




u 






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B 














































































































































































































































































40 


























































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Fig. 10. 



342 



THE STATIC TRANSFORMER. 



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1.000 
1^250 
1,500 
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1,500 
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1,500 
1,800 
2,000 
2,500 
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10,000 


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tHCNCO'*IO©1>CO©©'-HCNCO>*LO©I>.CO©©i-i 



GENERAL ELECTRIC TYPE H TRANSFORMERS. 



343 



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3 3 * 

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8 8 § 



344 



THE STATIC TRANSFORMER. 



Magnetic fatigue or aging of iron subjected to magnetic reversals 
is now well recognized, and precautions are taken to prevent it by all tlie 
better class of transformer manufacturers. Unless great care is taken in 
tliis respect the core loss is liable to increase very considerably after time has 
elapsed, this loss increasing from 25 % to often more than 100 % of the ori- 
ginal core loss. The following curves show the difference between carefully 
selected and prepared iron, and ordinary commercial iron. The upper curve 
shows a very great increase in iron loss after 80 days' run, while the two 
lower curves show but little increase after the same length of time. 

Curves 9 and 10 also show results of aging tests by Mr. W. F. Parshall and 
Mr. A. H. Ford. 



110 


































































































































































































































+ 














100 


































































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NC 


RE 


ASE 




















































































































































































































































90 










































































































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80 













































- CORE |LO'ss|d6e [to! AGEING 


















































































































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CURVE SHOWS RESULTS OBTAI 


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ON AJ TRANSFORMER! RECEN 


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1 III 









I 20 30 40 50 60 70 80 

DAYS RUN J, _^ 

CURVES SHOWING INCREASE OF TRANSFORMER CORE LOSS. DUETTO .AGEING 

Fig. 11. 



Regulation. 

The most important factor in the life of incandescent lamps is a steady 
voltage, and a system of distribution in which the regulation of pressure is 
not maintained to within 2 % is liable to considerable reduction in the life 
and candle power of its lamps. For this reason it is highly important that 
the regulation, i.e., the change of voltage due wholly to change of load on 
the secondary of a transformer, be maintained within as close limits as 
possible. 

In the design of a transformer, good regulation and low-core loss are in 
direct opposition to one another when both are desired in the highest de- 
gree. For instance, assuming the densities will not be changed in the iron 
or in the copper, if we cut the section of the core down one-half, we decrease 
the core loss one-half. The turns of wire, however, are doubled, and the 
reactance of the coils quadrupled, because the resistance changes with the 
square of the turns in series. 

A well-designed transformer, however, should give good results, both as 
regards core loss and regulation, the relative values depending upon the 
class of work it is to do, and the size of the transformer. The following 
table shows the results of tests for regulation of a number of commercial 
transformers obtained in the open market by Mr. Ford. 



REGULATION OF TRANSFORMERS. 



845 





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346 



THE STATIC TRANSFORMER. 



Comparative Expense of Operating- JLarg-e and Small 
^Transformers. 

It is obvious that the design of the distributing system has quite as much 
to do with the maintenance of a steady voltage as does the regulation of the 
transformers, and the proper selection of the size of transformers to be 
used requires skilled judgment. 

When transformers were first used it was the custom to supply one for 
each house, and sometimes two or three where the load was heavy. Expe- 
rience and tests soon made it evident that the installation of one large 
transformer in place of several small ones was very much more economical 
in first cost, running expenses (cost of power to supply loss), and regulation. 

Where transformers are supplied one for each house, it is necessary to 
provide a capacity for 80 % of the lamps wired, and allowing an overload of 
25% at times. Where one large transformer is installed for a group of houses, 
capacity for only 50% of the total wired lamps need be provided. For resi- 
dence lighting, where the load factor is always very low, it is often best to 
run a line of secondaries over the region to be served, and connect a few 
large transformers to them in multiple. 

A study of the following curves will show in a measure the results to be 
expected by careful selection and placing of the transformers. The first 
curve, Fig. 12, shows the relative cost per lamp or unit of transformers of 
different capacity, showing how much cheaper large ones are than small 
ones. 



fc2 

to 
O 




































1 


























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> 1 
1- 






V 


























































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f?0 




































































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2 


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IG1- 


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TS 





5( 





6( 








Fig. 12. Relative Cost of Transformers of Different Capacities. 

The second set of curves, Fig. 13, shows the power saved at different loads, 
and using different sizes of transformers. 



200 



CURVES SHOWING POWER SAVED 
AT DIFFERENT LOADS 
» 'BY THE USE-OF 
LARGE TRANSFORMERS 
-CURVE NO. 1 WATTS LOSS IN 1 50d LIGHT TRANSFORMER 




Fig. 13. Relative Efficiency of Large and Small Transformers. 



COMMERCIAL TRANSFORMERS. 



347 



Power factor is the ratio of the actual watts in a line to the volt 
amperes or apparent watts in that line. It is also defined as the cosine of 
the angle of phase displacement of the current from the voltage in the 
circuit. 

The power factor of most commercial transformers is low at no load, 
varying from 50 % to 70 %, while at high loads the power factor is very 
nearly 100 per cent. For this reason it is better to distribute the trans- 
formers on the line so that they will carry load enough most of the time to 
keep the power factor reasonably high. 

COM1EERCIAL TIUXMOBMEII*. 

The following tables show the trade numbers, capacities, and the ordinary 
characteristics of some of the transformers in more oommon use at this 
time, including Stanley Electric Co. : Westinghouse Electric and Manufac- 
turing Co. ; " "Wood," the Fort Wayne Electric Corporation ; Wagner 
Electric and Manufacturing Co. ; General Electric Co., table for which will 
be found on page 343. 

In order to show a comparison of the qualities of transformers as made 
some time ago and at present, a table of tests by Dr. Fleming, F.R.S., is 
also included. 



STABflEY ELECTRIC MAlVUEACTITItllVG CO. 
LIGHTING TRAIIEORMERS, 

Frequency = 66 P.P.S. 

Efficiencies. 

Regulation uniformly 2£ % at full load. 



Type. 


Full 

Load 

Output 

in 
K.W. 


Full Load. 


| Load. 


\ Load. 


J Load. 


\ Load. 


2G 


i 


93.0% 


93.1% 


92.2% 


88.8% 


80.7% 


3G 


1 


93.0 


93.2 


93.0 


89.5 


82.5 


4G 


1 


95.5 


95.7 


95.0 


92.0 


85.0 


6G 


n 


95.8 


96.0 


95.5 


92.8 


87.6 


8G 


2 


95.9 


95.9 


95.5 


93.5 


88.5 


10 G 


n 


96.0 


96.2 


95.8 


93.5 


90.4 


15 G 


3| 


96.6 


96.7 


96.3 


94.3 


91.3 


20 G 


5 


96.7 


96.9 


96.6 


95.0 


91.5 


30 G 


7| 


96.8 


97.0 


96.7 


95.5 


92.2 


40 G 


10 


96.8 


96.9 


96.8 


95.7 


92.6 


60 G 


15 


97.2 


97.2 


97.2 


96.9 


94.8 


80 G 


20 


97.8 


97.7 


97.5 


96.9 


95.1 


100 G 


25 


97.6 


97.8 


97.8 


97.2 


95.5 



348 



THE STATIC TRANSFORMER. 





















































.p. ft. 


























H 
























FULL LOAD 97.91 
7 8 " ?7-91 


5* 






>- 
o 

z. 
















3 / 4 




' 97. 86 
( 97.49 


J 






5 
















1 /a 




< 95.89 

< 92.47 








■ss. 
















REGULATION 


1 1 / 2 J5 








/ 














| TYPE fl-OO-W. 
POWER TRANSFORMER 






/ 














ST 


ANLEY ELECTRIC M'F'G CO. 

4-20-93. 




, 




1 




OUT 


PUT 


N K1L 


DWAT 


c_ 













Fig. 14. 



































98 
97 
96 
95 

94 
93 
92 
01 
90 




















EFFIC 


IENCN 


AT 


33 P. 


P. 8. 




















FUL 
7 "8 


L LC 


)AD 


98.1 
98.15 


To 
























i 


( 


98.14 
97.91 


% 






> 
o 

z 




/ 












1 A 
Va 


; 




96.69 
93.96 








LL 


/ 


i 












RE 


GULA 


TION 


IV, 


i 






■feS. 


/ 












































P 


tVpe 4oo-vy. 

OWER TRANSFORN 


ER 




















ST 


<\NLE 


Y ELECTRIC 


M'F'G CO. 
1 4-20-' 


s. 












OUT 


PUT 1 


N KILOWAT 


TS 


















25 








50. 








75. 






100 



Fig. 15. 



STANDARD C. S. TRANSFORMERS. 



349 



STANDARD C. S. TRAXftJFORJIERK OJF WEKTIXCl- 
IIOOE ELECTRIC A]¥» MAHflJFACTEROft CO. 



Iron JLosses. 







Tr 


ue. 


Apparent. 


Size. 


Watts. 












A=rl33£ 


A=60 


ir= 1331 


A=60 


1 


250 


6.80% 


9.40% 


8.90% 


13.00% 


2 


500 


5.20 


6.80 


6.60 


9.70 


4 


1000 


3.00 


4.10 


3.70 


5.60 


6 


1500 


2.50 


3.30 


3.20 


4.70 


8 


2000 


2.20 


2.90 


2.80 


4.10 


12 


3000 


1.70 


2.20 


2.20 


3.10 


16 


4000 


1.70 


2.20 


2.20 


3.10 


20 


5000 


1.60 


2.10 


2.10 


2.85 


25 


6250 


1.57 


2.05 


2.02 


2.84 


30 


7500 


1.54 


2.00 


1.90 


2.70 


40 


10000 


1.30 


1.70 


1.71 


2.31 


50 


12500 


1.06 


1.40 


1.40 


1.85 


60 


15000 


1.02 


1.32 


1.35 


1.80 


75 


18750 


0.92 


1.20 


1.17 


1.61 


100 


25000 


0.86 


1J2 


1.12 


1.53 



STANDARD C. S. TRA]¥SrORMER§ OP WESTING- 
HOUSE ELECTRIC AUD MAHEFACTERIIHJ CO. 



Efficiencies. 





Full Load. 


1 
| Load. 


\ Load. 


\ Load. 






















A=133i 


A=60 


A"=133i 


A=60 


N—\Z'6\ 


A =60 


A=133i 


N— 60 


1 


90.3% 


87.7% 


88.8% 


85.3% 


84.7% 


79.8% 


71.6% 


62.0% 


2 


91.7 


90.1 


90.7 


88.7 


88.0 


84.9 


78.4 


72.0 


4 


94.0 


93.0 


93.8 


92.3 


92.5 


90.3 


97.3 


83.0 


6 


94.5 


93.6 


94.3 


93.3 


93.4 


91.8 


89.2 


86.0 


8 


95.1 


„94.4 


95.0 


94.1 


94.3 


92.8 


90.5 


88.8 


12 


95.8 


95.2 


95.8 


95.1 


95.4 


94.3 


92.6 


90.5 


16 


96.34 


95.8 


96.3 


95.5 


95.7 


94.6 


92.8 


90.7 


20 


96.5 


96.0 


96.34 


95.8 


95.85 


96.8 


93.1 


91.1 


25 


97.0 


96.54 


96.83 


96.23 


96.15 


95.23 


93.36 


91.52 


30 


96.96 


96.50 


96.72 


96.21 


96.17 


95.25 


93.47 


91.63 


40 


97.04 


96.64 


97.02 


96.49 


96.56 


95.76 


94.35 


92.75 


50 


97.24 


96.90 


97.31 


96.86 


97.03 


96.35 


95.34 


93.98 


60 


97.38 


97.08 


97.44 


97.04 


97.16 


96.56 


95.52 


94.32 


75 


97.48 


97.20 


97.58 


97.20 


97.36 


96.80 


95.92 


94.80 


100 


97.74 


97.48 


97.81 


97.45 


97.58 


97.06 


96.21 


95.17 



350 



THE STATIC TRANSFORMER. 





























o 


a 


co 

CO 


os 

CO 


CO 
CO 


S 


CI 
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00 




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os 


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IN 


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CO 


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crt 








fl 






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A 






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WAGNER TRANSFORMERS. 



351 



fi 



g 1 | 

Coo 

ft § * 

« co Z 

M ^ .5 



1 © 





>3 























CM 


s 


CN 


8 


8 


CO 
CN 


8 


S 




d 


83 


t-^ 


CO 


d 




CN 


CN 






oo 


00 


00 


OS 


OS 


OS 


OS 
























«1 






















t~ 


o 




00 


8 


OS 


o 


t- 




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CO 


os 


5 


© 


OS 




co 




A 


8 


id 

t- 


g 


oo 


28 


£ 


00 


88 




-is 




















■d 

o 




co 


CM 


OO 


OS 


CO 


o 


cS 


• 


CO 


CO 


CM 


q 


LO 


m 




.2 


ss 


00 
00 


s 


OS 


cn 

OS 


d 

OS 


OS 


$ 


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S3 


H(* 


















<D 




















O 






































sfi 




















0) 


>d 

O 


OS 
00 


CD 

o 


o 


3 


CO 


q 


CO 


s 


d 


CO 


Tin 


Tji 


id 


d 


d 


d 


os 


OS 


OS 


OS 


OS 


OS 


OS 


OS 


O 


hn 


















J-l 








































A 


d 
c3 

o 


CO 


8 


CO 


ss 


CO 


CN 

cp 


OS 


8 




A 


cn 


£ 


id 


id 


d 


d 


d 


d 




os 


OS 


OS 


cs 


OS 


OS 


os 




nw 






































03 

o 


£§ 


OS 


o 




CO 


o 


CN 


oo 




CD 


■* 


00 


CN 




q 






^ 


CO 


3 


id 


id 


d 


d 


t^ 






OS 


OS 


OS 


OS 


OS 


OS 


OS 




*"* 


















,_; 




















cS 


t- 




CO 


:* 


IO 


CO 


CN 


m 




o 


t>; 




CO 


t~ 




in 


OS 


q 




h] 


CO 


i 


id 


id 


d 


d 




t^ 






OS 


OS 


OS 


os 


OS 


OS 


OS 




^ 


















Per 
Cent 

of 
egula- 
tion. 




s 


o 
in 


s 


o 
co 


Q 


o 
os 


o 
os 


cn 


cn 


cn 


CN 


CN 


CN 


TH 


rH 


tf 


















Per 

Cent 

of 
opper 

Loss. 


io 


!S 


in 

CN 


q 


8 


00 


co 


CO 


cn 


CN 


<n 


CN 


CN 


1-H 


1-1 


i-l 


© 


















Per 

Cent 
of Iron 

Loss. 


OS 

co 


lO 




CO 


oo 


eo 


m 

CD 


CO 


*#* 


CO 


cn 


CN 




1-1 


^ 


" 




1 


g 


s 


8 


8 


§ 


o 

8 


8 


1 


£ 


s 
£ 


» 


o 


1C 


<M 


s 


S 


CN 

CO 


"3 

68 






































a 




















cS 


co 


















© 


ll 

3 


o 


8 


© 

CO 


^ 


8 


8 


8 


I 



352 



THE STATIC TRANSFORMER. 





>-> 


co 

CO 


00 


3 


rH 


28 


fc- 


00 
00 


CO 

m 


s 


CO 
05 


3 




© 


t 


& 


00 


OS 


rH 


_; 


cs 


eo 


CO* 


•* 






00 


00 


00 


CO 


CS 


© 


© 


© 


CS 


OS 






























«J 


























o 


8 


§° 


OS 
CO 


© 


s 


s 


© 


8 


© 


t> 


© 

CO 




i-q 


© 


no 


os 




rj 


3 




00 


cs 


© 






co 


t- 




00 


CO 


CO 


00 


co 


© 


© 




eg 


2 


« 


m 


© 


m 
in 




8 


CD 

CD 


q 


CO 


CO 
C5 


© 


o 


£ 


00 
CO 


i 


OS 


c4 

© 


S3 
© 


$ 


i 


in 
© 


J9 

OS 


CO 

© 


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o 


























'o 


























=e 


























s 




cn 


00 


rH 




m 


CO 






CO 


l^ 








00 


OS 


in 


CO 


OS 


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co 


CO 


CJ 


in 




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ci 


CO 


£ 


in 


in 


CO 




CD 


t>°. 


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s 


os 


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os 


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cs 


cs 


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H W 












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CO 


o 


in 


N 


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se 


OS 


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CO 


cs 




in 




OS 


Tfj 


m 


co 


os 


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in 


CD 




C5 




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in 


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co 


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© 


cs 


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OS 


© 


OS 


© 


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© 


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c3 
O 
hi 


s 


9 


S 


CO 

in 


8 


CO 

in 


CO 
CO 


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© 


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3 


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JO 


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CO 


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cs 


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1-1 
























d 


























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CO 


00 


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CO 


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CO 


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CS 


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CD 


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CO 


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CO 


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tf 


t^ 








CS 


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cs 


cs 


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Per 

Cent 
of 

egula- 
tion. 


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in 


m 


© 


m 


© 


© 


gg 


© 


© 


CO 


o 

CO 


CO 


in 


in 

ON 




<N 


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cs 


OS 


ti 
























j_. 
























Pei- 
Cent 
Coppe 
Loss, 


OS 


to 


8 


S3 


£ 


m 

cs 


00 


CO 


m 

CO 


CO 


CO 


ci 


c4 


ci 


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m 




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cn 


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CI 


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8 


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o 

o 


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o 

10 


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§ 


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o 
© 


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o 
© 


© 

8 


I 


© 

o 
m 


8 
8 


1 


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£ 




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a 


























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Jg 
























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2 


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o 


o 


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s 


© 


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m 


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© 


o 




be 




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CO 


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00 


<M 


m 


a 


© 

CO 




M 

























WAGNER TRANSFORMERS. 



o03 





tA 




















c$ 


3 


i2 


CO 
CI 


$ 


£: 


S 


© 
© 


© 






00 


oo 


s 


s 


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CO 

© 


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3 


















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o 


© 
en 


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CI 


s 


CO 


28 


s 


© 
Ci 




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■* 


3 


sg 


00 


00 


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oo 


ci 

CO 


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© 
























5 

O . 




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© 


© 




CO 


£9 


m 


CO 


t- 




CO 


© 


CO 


ra 


CO 


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t^ 


d' 


ci 


ci 


-* 


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S 


o 




oo 


Ci 


© 


Ci 


© 


Ci 


© 


© 




Hfcl 


















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CD 


OS 

o 


® 


CO 


<# 




25 


CO 


§8 


© 
ci 


ci 


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o 


CO 


© 


co" 




l-i 


os 


© 


Ci 


Ci 


© 


Ci 


© 


© 


O 


H|M 


















CD 






































Ph 


>d 




















c3 

o 


o 


CI 


So 


© 

CN 


fc 


3 


8 


3 




A 


cS 


id 


lO 


CO 


© 






t^ 






Ci 


© 


© 


© 


© 


© 




etf# 


















• 




















o 


s 


CO 


CO 
Ci 


© 


© 

CO 


i 


C5 


? 






cf 


© 


Ci 


CO 
© 


© 


© 


© 


© 




^ 


















-d 




















o 


3 


o 


CO 


© 




© 




© 




CN 


t-; 




■*. 


CO 




CJ 




■* 


LO 


o 


© 


© 


CO 


l> 


t^ 




i-W 


© 


© 


Ci 


© 


Ci 


Ci 


Ci 


© 




^ 


















«A • 


















hrtfld 


8 

CO 


m 


IO 


m 


© 


© 


© 


© 


Pe 

Cei 

Regi 

tio: 


© 

ci 


ci 


ci 


ci 


ci 


CJ 

ci 


CI 

ci 


j_! 


















Per 

Cent 
Coppe 

Loss 


o 

LO 


S 




o 


© 
© 


© 

CO 


8 


k 


ci 


ci 


ci 


ci 


ci 


1-1 


rH 


1-1 


Per 

• Cent 
Iron 

Loss. 


<M 


o 


Ci 


8 


JO 


-* 


cq 


Ci 


CO 

CO 


ci 


OS 




OJ 


CJ 


OS 


sA 


CO 


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356 



THE STATIC TRANSFORMER. 



SPECIAL TYPES OF TRANSFORMER. 

The ordinary static transformer is generally understood to be a constant 
potential transformer, which is adapted to operate when connected in 
parallel across a constant potential circuit. 

When transformers are designed for special uses, it is customary to 
designate them by name, indicative of the special work they are intended 
to perform. A few of these transformers are here described. 

Special High Potential Transformer. 

In making high potential tests of apparatus, it is very desirable to have a 
transformer Avhich is adapted to tbis work. 

The General Electric Company is now supplying a transformer designed 
for the purpose of making high potential tests up to 10000 volts. This trans- 
former is tested up to a pressure of 35000 volts, and is so constructed as to 
avoid any danger of breaking down as far as possible. Below is a cut, to- 
gether with a diagram of" its connections. 



104 VOLT MAINS' 
(OR 52 VOLTS WITH' 
CONNECTION 
BOARD IM PARALLEL) 




APPARATUS 
UNDER TEST 



WATER RHEOSTAT 



Fig. 16. 



The core is rectangular in form, the primary or low-tension side being 
wound on one leg of the core, while the secondary or high-tension side is 
divided into four separate coils, and mounted on a sleeve of heavy insulating 
material, and placed over the opposite leg, the whole being immersed in oil. 

A micrometer spark gap is mounted on top of the box or case, and con- 
nected in shunt across the high potential terminals. The spark gap is set 
for the desired voltage by the use of a calibration curve, or by a preliminary 
calibration bv means of a voltmeter connected to the low-tension side, the 
ratio of transformation being known. The apparatus to be tested is then 
connected to the high potential terminals, and the potential raised to the 
desired amount. 



SPECIAL TYPES OF TRANSFORMERS. 



357 



This transformer is most invaluable in testing all kinds of apparatus for 
high-tension work. 




Fig. 17. High Potential Testing Transformer. 

Transformers for Constant Secondary Current. 

Several methods have been tried with more or less success to obtain con- 
stant current at the secondaries of transformers. 

The simplest and earliest system for obtaining a constant current in the 
secondary is by means of transformers whose primaries are connected in 
series, and a constant current maintained in the primary. This is shown in 
diagram in Fig. 18. Series transformers for this purpose have never been 
very successful, due to the trouble caused by the rise of potential in the 
secondary when opened for any cause. Various devices (Fig. 18), such as 
short-circuiting points separated by a paraffined paper, or a reactive or 
choking coil connected across the secondary terminals, have been intro- 
duced to prevent any complete opening of the secondary by reason of any 
defect in the lamp or other device connected in the circuit. 



CONSTANT CURRENT LINE 




SERIES TRANSFORMERS 



REACTIVE 
COIL 



*-ARC LAMPS-* 

Fm. 18. 



SLSUL2SL 



Reactive coils used as shunt devices have been used under different 
names ; as compensators, choking coils, and economy coils. 



358 



THE STATIC TRANSFORMER. 



A device of this kind has been introduced by the Westinghouse Electric 
and Mfg. Company, and others, for use in street-lighting by series incan- 
descent lamps. It is shown diagrammatically in Fig. 19. The lamp is 
placed in shunt to the coil ; when the filament breaks, the total current 
passes through the coil, maintaining a slightly higher pressure between its 
terminals than when the lamp is burning. It is thus evident that the regu- 



r^n r °i r^ 

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C0NSTANT 
POTENTIAL 



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Fig. 19. 



lation of the circuit is limited, due to the excessive reactance of the coils 
when several lamps are taken out of circuit. 

Economy Coils or Compensators. 

A modification of the above is built by several companies for use on ordi- 
nary low potential circuits, where it is desired to run two or three arc 
lamps. It is a single coil transformer, and is shown in Fig. 20, and diagram- 
matically in Fig. 21, same page. If any lamp is cut out or open-circuited 
the current in the main line decreases slightly. As more lamps are cut out 



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D. P. SWITCH 
D. P. FUSE BOX 



LIGHT COMPENSATOR 




S. P. SWITCH 



Fig. 20. Westinghouse Econ- 
omy Coil. For A.C. arc lamps. 



Fig. 21. Arrangement of Apparatus for 
use of Economy Coil or Compensator. 

the remaining lamps receive less current, and it is necessary to replace the 
bad lamps in order to obtain normal current through the circuit. 



Transformei 



for Constant Current 
tential. 



from Constant Po- 



The transformers represented in Fig. 22 show a design that will give out 
an approximately constant current when connected to constant potential 
circuits. The transformer has its core so designed that there is a leakage 
path for the flux between the primary and secondary. This is shown in the 



SPECIAL TYPES OF TRANSFORMERS. 



359 



diagram at a and b. At open secondary circuit there is little or no ten- 
dency for the flux to leak across the gap. When current flows through the 
secondary, thus creating a counter magneto-motive force, there is then a 




Fig. 22. Constant Current or Series Transformer. 

leakage across this path, and if properly propoi-tioned, this leakage will act 
to regulate the current in the secondary, so that it will be approximately 
constant. 

General Electric Constant Current Transformers. 

The transformer .just described has the disadvantage that its regulation 
is fixed for any transformer, and may vary in transformers of the same 
design, without any ready means of adjustment. The transformer also 
regulates for constant current over but a limited range in the secondary 
loads. 

The General Electric Company constant current transformer shown in 
Figs. 23 and 24, is constructed with movable secondary coils, and fixed pri- 
mary coils. 




PRIMARY CIRCUIT 




Fig. 23. General Elec. Co. 
Constant Current Trans- 
formers for 50 lights. 



FIG. 24. Connections for Alter- 
nating Series Enclosed Arc 
Lighting System, with 50, 75, or 
100 Light Transformer. 



The weight of the movable coil is partially counterbalanced, so that at 
normal full-load current the movable coil or coils lie in contact (See Fig. 
25) with the stationary coil, notwithstanding the magnetic repulsion between 
them. When, however, one or more lamps are out of the circuit, the in- 
creasing current increases the repulsion between the coils, and separates 
them, reducing the current to normal. (See Fig. 26.) At minimum load, the 
distance between the coils is maximum. The regulation is thus entirely 
automatic, and is found to maintain practically constant current, or a de- 
parture from constant current if desired. The transformer can be adjusted 
for practically constant current for positive regulation ; i.e., increasing 
current from full load to light loads, or for a negative regulation, i.e., de- 
creasing current, from full load to light loads. This adjustment is obtained 



360 



THE STATIC TRANSFORMER. 



by changing the position of a cam from which the counter-weights are sus- 
pended. The curves shown in Fig. 28 show the range obtained in a 100-light 
transformer. 




Fig. 25. Full-Load Position 
of Secondary Coils. 




Fig. 26. Half-Load Position 
of Secondary Coils. 



The transformers are enclosed in cast iron or sheet iron tanks filled with 
transil oil. The oil, in addition to being an insulating and cooling medium, 
serves to dampen any sudden movement of the secondary coils. 

These transformers are connected to the regular constant potential mains, 
and the larger sizes are arranged for multiple circuits in the secon- 
dary. After having been started on a run, the transformers need no atten- 
tion, as they are entirely automatic in their action. 



SECONDARY *. 
.SWITCH ,_>< y x_J 

ARC LAMP 
, VOLTS 




Fig. 27. Diagram of Connections. 

The full-load efficiency of this type is practically the same as that of a 
constant potential transformer of the same capacity. The power factor of 
the system at full load is about 85 per cent, due to the reactance of alternat- 
ing arc lamps. At fractional loads, the power factors necessarily are much 
lower, and it is therefore not desirable to operate such a system at light load. 



7.5 

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Fig. 28. 



REGULATING REACTANCE COIL. 



361 



RE«ILATII(} REACTANCE COIL FOR A. C. ARC 
CIRCUITS. 

Another and very simple device for regulating the current in a series cir- 
cuit for A.C. arc lamps has been put on the market by the Manhattan Gen- 
eral Construction Company. It consists of a single coil of insulated wire 
arranged to enclose more or less of one leg of a "W"-shaped magnet, as 
shown in the following cut. The coil is suspended from one end of a lever 




Fig. 29. Regulating Reactance Coil by Manhattan General Construction Co. 

and counterbalanced by a weight on the other, and so arranged that at all 
points of its travel it just balances the varying magnetic pull of the coil. 
The arc circuit is connected in series with this coil with a switch to open 
the circuit. Without current flowing, the normal position of the coil is at 
the top or off the leg of the magnet. When the switch is closed, current 
flows in the circuit (and coil), and draws the coil down on the leg to a point 
where the reactance of the coil holds the current strength at a predeter- 




Fig. 



30. Diagram of Connections of the Regulating Reactance Coil 
of the Manhattan General Construction Co. 



562 



THE STATIC TRANSFORMER. 



mined point ; as, say, 6.6 amperes. It is said that this device will maintain 
a current constant within one-tenth of an ampere. 

The losses are the iron losses and I 2 Ii losses in the coil, which, with con- 
stant current, are the same under all conditions of load. 

As it is not always, or even often, that it is necessary to provide for regu- 
lation of an arc circuit to the extent of its full load, the makers have 
adopted the policy of supplying instruments to care for but that part of the 
load that is expected to vary, in some cases 10 % of the circuit and in others 
75 %, thus avoiding the need for larger apparatus, or for insulation for the 
total voltage of the circuits. They claim another advantage in being able 
to connect the device in one leg of the series circuit, and allowing the other 
end of the circuit to be connected to the mains at any such point as may be 
the nearest at hand. Fig. 30 shows the apparatus diagrammatically. 




Fig. 31. 



feeder Regulators. 



An alternating current feeder regulator is essentially a transformer hav- 
ing its primary connected across the mains, and its secondary in series with 
the mains. The secondary is arranged so that the voltage at its terminals 
can be varied over any particular range. 




Fig. 32. Internal Connections of a Stillwell Regulator. 



REGULATING RESISTANCE COIL. 



363 



The several different styles of feeder regulators have been devised, differ- 
ing in principle of operation, but all of them have the primary coil con- 
nected across the mains, and the secondary coils in series with the mains. 

The " Stillwell " regulator, which was designed by Mr. L. B. Stillwell, has 
the usual primary and secondary coils, and effects the regulation of the cir- 
cuit by inserting more or less of the secondary coil in series with the line. 
This secondary coil has several taps brought out to a commutating switch, 
as shown in Fig. 31. The apparatus is arranged so that the primary can 
be reversed, and therefore be used to reduce as well as to raise the voltage 
of the line. It is evident from an observation of the diagram that if two 
of the segments connected to parts of the coils were to be short-circuited, it 
would be almost certain to cause a burn-out. To prevent this, the movable 
arm or switch-blade is split, and the two parts connected by a reactance, 



KAPPS MODIFICATION 
OF STILLWELL REGULATOR 




Fig. 33. 

this reactance preventing any abnormal local flow of current during the 
time that the two parts of the switch-blade are connected to adjacent seg- 
ments. The width of each half of the switch-arm must of necessity be less 
than that of the space or division between the contacts or segments. 

As the whole current of the feeder flows through the secondary of the 
booster, the style of regulator which effects regulation by commutating 
the secondary cannot well be designed for very heavy currents because of the 
destructive arcs which will be formed at the switch-blades. To overcome 
this difficulty, Mr. Kapp has designed the modification which is shown in 
Fig. 33. In this regulator the primary is so designed that sections of it can 
be commutated, thus avoiding an excessive current at the switch. This 
regulator, however, has a limited range, as the secondary always has an 
E.M.F. induced in it while the primary is excited ; and care must be taken 
to see that there are sufficient turns between the line and the first contact 
in order to avoid excessive magnetizing current on short circuit. 




Fig. 34. Connections for M. R. 
Feeder Regulator of G. E. Co. 




HAISE 
V0LTAGE.E1Z2) LOWER VOLTAGE 

<CONTRJ>UINQ HAND \ 



Fig. 35. Diagram of Con- 
nections of Feeder Po- 
tential Regulator. 



The General Electric Company have brought out a feeder regulator, 
which there are no moving contacts in either the primary or secondary, a 



in 

tng contacts m eittier the primary or secondary, and 
which can be adapted for very heavy currents. This appliance is plainly 
shown in Figs. 34 and 35. The two coils, primary and secondary, are set at 
right angles in an annular body of laminated iron, and the central lami. 



364 



THE STATIC TRANSFORMER. 



nated core is arranged so as to be rotated by means of a worm wheel and 
shaft as shown. 

The change in the secondary voltage, while boosting or lowering the line 
voltage, is continuous, as is also the change from boosting or lowering, or 
vice versa. In this regulator, the change of the secondary voltage is effect- 
ed by the change in iiux through the secondary coil, as the position of the 
movable core is changed by the turning of the hand wheel and shaft. There 
are, therefore, no interruptions to the flow of current through either the 
primary or secondary coils, and the regulator is admirably adapted for in- 
candescent lighting service, where interruptions in the flow of current, how- 
ever instantaneous, are objectionable. 



8. K. C. DEVICES FOR REGULATING A. 
CIRCUITS. 



C. 



Where polyphase A. C. generators are used for lighting and power it is 
necessary to provide some method by which the individual phases can be 
separately and independently regulated. 

The method used by this company for accomplishing this result is by 
changing the effective turns on the armature. At one end of the winding 
of each phase are several regulating coils from which are brought out to 
suitable regulator heads taps which are mounted upon a terminal board 
fastened to the machine ; or the regulator heads, if so desired, may be 
mounted upon the switch-board. The following diagrams illustrate 
the method of bringing out the regulating taps from the armature coils of a 
two-phase generator. 




Fig. 36. Two-phase Generator. 



The regulator heads are similar to those used in connection with the 
"Stillwell" regulator, and make use of a modification of the split finger 
contact arm and choke-coil to prevent short circuit of the regulator coils. 



DEVICES FOR REGULATING A. C. CIRCUITS. 365 



PHASE A-B PHASE E-F 




CIRCUIT 
No. 1 

Fig. 37. Diagram of one Two-phase Generator and four Circuits. 



GENERATOR NO. 1 
PHASE A-B PHASE E-F 



GENERATOR NO. 2 
PHASE A-B PHASE E-F 



mm 

9 




Fig. 38. Diagram of two Two-phase Generators in Parallel and three 
Circuits. 



366 THE STATIC TRANSFORMER. 



Separate Circuit Reg-ulations. 

Where a number of circuits are run out from the same set of bus bars, 
regulation of each circuit is provided for in this system by the use of a 
single coil transformer from various points on the winding of which leads 
are brought out to a regulator head, from which any part or all of the trans- 
former may be thrown into service to increase the pressure on the line. 

Figures 37 and 38 show in diagram the method of applying this device, 
which is also provided with the split finger contact and choke-coil to prevent 
short circuit. 

TRANSFORMER CONNECTIONS. 

Some of the advantages claimed for alternating current systems of dis- 
tribution over the direct current systems is the facility with which the 
potential, current, and phases can be changed by different connections of 
transformers. 

On single-phase circuits, transformers can be connected up to change 
from any potential and current to any other potential and current ; but in 
a multi-phase system, in addition to the changes of potential and current, 
the phases can be changed to almost any form that may be desired The 
following diagrams, taken from General Electric Company publications, 
represent some of the results obtained by different transformer con- 
nections. 

Directions for Connecting* Type H, Cr. JE. Transformers. 




Figs. 39 and 40. 

Transformers Wound for 1040 or 2080 Volts Primary and 52 or 104 

Volts Secondary. 

For 1040 volts primary and 52 volts secondary, See Fig. 39. 

" 1040 •• " " 104 " « " « 40. 

« 2080 »« " " 52 " " « « 43. 

» 2080 " " •' 104 » •< " « 44. 

Transformers Wound' for 1040 or 2080 Volts Primary and 104 or 208 
Volts Secondary . 

For 1040 volts primary and 104 volts secondary, See Fig. 39. 

" 1040 " " " 208 " » « «' 40. 

" 2080 " " " 104 " " « " 43. 

" 2080 " " " 208 " •' " " 44. 

Transformers Wound for 1040 or 2080 Volts Primary and 115 or 230 
Volts Secondary. 

For 1040 volts primary and 115 .volts secondary, see Fig. 39. 

" 1040 " " " 230 " « *< " 40. 

" 2080 » " " 115 " •• " " 43. 

" 2080 " " " 230 •« " " " 44. 



TRANSFORMER CONNECTIONS. 



36" 




Figs. 41, 42, and 43. 
Transformers Wound for 1040 or 2080 Volts Primary and 115 Volts 

Secondary. 

For 1040 volts primary and 115 volts secondary, see Fig. 41. 

" 2080 " " " 115 " " '• " 43. 

Transformers Wound for 520 or 1040 Volts Primary and 115 or 230 

Volts Secondary. 

For 520 volts primary and 115 volts secondary, see Fig. 39. 

" 520 " " " 230 " " " " 40. 

" 1040 " " " 115 " " " " 43. 

u 1040 .< t . « 230 " " " " 44. 

Transformers Wound for 520 or 1040 Volts Primary and 115 Volts 
Secondary. 
For 520 volts primary and 115 volts secondary, see Fig. 39. 
" " 115 " " " " 43. 



1040 



rCTf 

¥ 





Figs. 44, 45, and 46. 

Transformers Wound for 1040 or 2080 Volts Primary and 52 or 104 

Volts Secondary, Used on Three- Wire System. 

For 1040 volts primary and 52-52 volts secondary, see Fig. 42. 

" 2080 " " " 52-52 " " " " 46. 

Transformers Wound for 1040 or 2080 Volts Primary and 104 or 208 

Volts Secondary, Used on Three-Wire System. 

For 1040 volts primary and 104-104 volts secondary, see Fig. 42. 

" 2080 " " " 104-104 " " " " 46. 

Transformers Wound for 1040 or 2080 Volts Primary and 115 or 230 

Volts Secondary, Used on Three-Wire System. 

For 1040 volts primary and 115-115 volts secondary, see Fig. 42. 

" 2080 " ' " " 115-115 " " " " 46. 

Transformers Wound for 520 or 1040 Volts Primary and 115 or 230 

Volts Secondary, Used on Three-Wire System. 

For 520 volts primary and 115-115 volts secondary, see Fig. 42. 

" 1040 " " " 115-115 " " '" " 46. 

All voltages for which a transformer is wound are stamped on the name 

plate on the cover of the transformer box. These are the normal voltages, 



368 



THE STATIC TRANSFORMER. 



for which the transformer is designed, but all transformers can be used 
satisfactorily for voltages that do not vary more than 10% above or below 
the designed voltage. 

Single-Phase. 

The connections of the single-phase step-down and step-up transformers, 
having parallel connections, need not be explained outside of the preceding 
diagrams. For residence lighting, the most economical method of supply 
is through single-phase transformers with three-wire secondaries. A tap 
is brought out from the middle of the secondary winding, this tap connect- 
ing to the middle or neutral of the three-wire system. In this way a few 
large transformers can be connected by three-wire secondaries in a resi- 
dence or other district, and will take care of a large number of connected 
lamps. 




BALANCING TRANSFORMER 



Fig. 47. 



Arrangement of Balancing Transformer for 
Three-wire Secondaries. 



Kapp shows a modification of the three-wire circuits, in which the out- 
side wires are fed by a single transformer, and the neutral wire is taken 
care of by a balancing transformer, connected up at or near the center of 
distribution. The capacity of the balancing transformer need be but half 
the greatest variation in load between the two sides. 

Some makers of transformers have the connection board in their trans- 
formers so arranged that the two primary coils may be connected either in 



mmmsms) 



(WMmmmv 








Fig. 49. Single-Phase, 

Fig. 48. Single- with S-wire Secondary, FlG - 50. Two- 
Phase. Useful for Residence Phase, 4 
Circuits. Wires. 



Fig. 51. Thre 

Wire, Two 

Phase. 



series or parallel by mere changes of small copper connecting links, so 
that the same transformer can be connected up for eitber 1000- or 2000-volt 
circuits, and the secondary for either 50 or 100 volts. 

Quarter-Phase. 

The plain two-phase or quarter-phase connection, Fig. 50, is simply two 
single transformers connected to their respective phases, the phases being 
kept entirely separate. In the three-wire, quarter-phase circuit, one of the 
leada can be used as a common return, as shown in Fig. 51. 



TRANSFORMER CONNECTIONS. 



369 



Three-Phase. 

The three-phase connections shown in diagram 52 are known as the 
delta connections, and are of great advantage where continuity of ser- 
vice is very important. The removal of any one transformer does not inter- 






Fig. 52. Three-Phase 
Delta Connection. 



Fig. 53. Three-Phase 
Star Connection. 



Fig. 54. Monocyclic 
Connections. 



rupt the three-phase distribution, and the removal of two transformers still 
admits of power transmission on a single phase of the circuit. 

The " Y " or star connection, as shown in diagram 53, has one of the 
terminals of each primary and secondary brought to a common connec- 



CENERATOR 



jWUx 



(wimp* 









Oa 






STEP UP 

TRANSFORMER 



Fig. 55. Connections of Mono- 
cyclic System for Light and 
Power. 




STEP DOWN 
TRANSFORMER 



Fig. 56. Changing Quarter-phase to 
Three-phase, Non-interchangeable 
Step-up Transformers. 



tion, the remaining three terminals being brought to the main line and the 
distributing lines. The advantage of the star connection over the delta con- 
nection is, that for the same transmission voltage each transformer is wound 



370 



THE STATIC TRANSFORMER. 



for only 58% of the line voltage. In high-voltage transmission this admits 
of much smaller transformers being built for high potentials than is possi- 
ble with the delta connection. 

Diagram 55, p. 369, shows a device by Mr. C. P. Steinmetz for enabling 
the lights and motors to run on the same single-phase circuit. The genera- 
tor has a supplemental coil called the teazer ; one end of this coil is con- 
nected into the middle of the main winding, the other being connected to 
the power wire or teazer Avire of the system. For lighting circuits, connec- 
tions are made only to the two outside wires, or the main wires of the sys- 
tem, or if it is desired to run three-wire system, the middle connection is 
made in the middle of the main winding. Where motors are connected up, 
the third connection is made to the teazer or power wire. This wire sup- 
plies current to the motor only during the time of starting, because as soon 
as the motor is up to synchronism it will then run as a single-phase machine, 
and no current is taken from the teazer wire. 



Arrangement of Transformers for Stepping- Up and Down 
for liOng- Distance Transmission- 
Figures 56,57, and 58 show diagrammatically the connections for adapting 
three-phase transmission to quarter-phase generators, with interchangeable 
and non-interchangeable transformers. The diagrams are probably suffi- 
ciently clear for the purposes of this article. 



GENERATOR 




Fig. 57. Changing Quarter- 
phase to Three-phase, and 
back to Quarter-phase. 
All Transformers Inter- 
changeable. 



GENERATOR 




<2000-Vr* 
JUUASJLai STEP UP 



TRANSFORMERS 



uww^mxmj^wzm) STEP D0WN 




-0-*a 

FlG. 58. Changing Quarter- 
phase to Three-phase. All 
Step-up Transformers Inter- 
changeable. 



Three-Pliase to Six-Phase Connections. 

A rotary converter wound for six-phase has a greater capacity for work 
than the same machine wound for three phases. Three-phase transmission, 
however, is very economical, and in Fig. 59 is shown a diagram by which six 
phases can be obtained from three phases by the use of only three trans- 
formers. 

Each transformer has two secondary coils. One secondary of each trans- 
former is first connected into a delta, then the remaining secondary coils are 



TRANSFORMER CONNECTIONS. 



371 



connected up into a delta, but in the reverse order of the first delta. This 
is an equivalent of two deltas, one of which is turned 180° from the other. 
In the diagram ABC represents one delta, and DEF the other. 



tvwvw^ pvwvwfj - Wwvw 
rAU/VWW-^i rAVWW-^n rAMAW-i 




Fig. 59. Diagrams of Connections for Changing from Three-Phase to 
Six-Phase. 

In the same way the two secondaries can be connected up " Y," and one 
" Y " turned 180° to obtain six phases. The disadvantage of " Y connec- 
tion, however, is that in case one transformer is burned out, it is not possi- 
ble to continue running, as can be done with delta connections. 




Ftg. 60. Method of Handling and Install- 
ing Transformers. 
From pamphlet of General Electric Company. 



lU'A 



THE STATIC TBANSFORMEB. 



TSSA^&FOIOIB^S TESTIIfi. 

Although the standard types of transformers of to-day are made on lines 
found by long experience to be the best for all purposes, and are subject to 
careful inspection and test at the factory in most cases, yet the various 
makers have such different ideas as to the value of the different points, 
that in order to obtain fair bids on such appliances when purchased, it is 
always best to prepare specifications, and the buyer should be prepared to 
conduct or check tests to determine Avhether the specifications have been 
fulfilled. Large stations should have a full outfit of apparatus for conduct- 
ing such tests ; but smaller purchasers can do quite well by having a compe- 
tent superintendent, or by hiring an outside engineer to Avitness the tests at 
the factory. It is not always necessary to put each individual transformer 
through all the tests, but the break-down test for insulation should be ap- 
plied to all. 

Prof. Jackson gives the following requirements for guaranties of trans- 
formers. 

Iron loss for 1000-volt transformers and for frequencies over 100 as 
follows : 



Capacity. 


Iron Loss. 


Exciting Current. 


1000 watts 

1500 watts 

2000 watts 

2500 watts 

4000 watts 

6500 watts 

17500 watts 


30 watts 

40 watts 

50 watts 

60 watts 

80 watts 

100 watts 

150 watts 


.055 amperes. 
.080 amperes. 

.150 amperes. 
.200 amperes. 



For frequencies less than 100 it may be advisable to allow 10 
to avoid excessive cost. 



higher loss 
Guaranties for iron loss should cover ageing for at least one 



Note. 
year. 

Drop in secondary pressure not to exceed 3 % between no load and full 
load. 

Rise of temperature after 10 hours' run under full load, 70° F. 
(about 40° C). 

Note. — This measurement was probably meant by Professor Jackson to 
be made by thermometer. It is better to take the rise by resistance meas- 
urement, in which case the allowable temperature is 50° C. 

Disruptive strength of insulation after full-load run, between 
coils and betAveen primary coil and iron, at least 10 times the primary volt- 
age. Insulation resistance to be not less than 10 megohms, and giiaranteed 
not to deteriorate Avith reasonable service. 

Note. — See previous matter as to test voltage. 

Exciting- current for 1000-volt transformers not to. exceed values 
given in the above table, Avhen the frequency is above 100. The exciting 
current increases as the frequency decreases, and varies inversely as the 
voltage. For intermediate capacities proportional values may be expected. 

He further says : " Transformers which do not meet the insulation and heat- 
ing guaranties are unsafe to use upon commercial electric lighting and motor 
circuits, while those which do not meet the iron loss, regulation, and exciting 
current guaranties waste the company's money.''' 

The characteristics of a transformer, to be determined by tests, are as 
folloAvs : * 

(1) Insulation strength betAveen different parts. 

(2) Core loss and exciting current. 

(3) Resistances of primary and secondary and PH. 

(4) Impedance and copper loss, direct measurement. 



TRANSFORMER TESTING. 373 



(5) Heating and temperature rise. 

(6) Ratio of voltages. 

(7) Regulation and efficiency, which may he calculated from the results 
of tests (2), (3), and (4), or may be determined directly by test. 

(8) Polarity. 

The instruments required to make these tests should be selected for each 
particular case, and consist of ammeters, voltmeters, and indicating watt- 
meters 

For central station work, the following instruments will suffice for nearly 
any case which may come up in ordinary practice. 

A. C. voltmeter, reading to 150 volts, and with multiplier to say 2500 volts. 

a! C. ammeter, reading to 150 amperes, with shunt multiplier if necessary 
to carry the greatest output. 

Indicating wattmeter, reading to 150 or 200 watts. 

Note. — For full data and examples of transformer testing , see pamphlet 
No. 8126, " Transformer Testing for Central Station Managers,'' by Gen- 
eral Electric Company. 

Insulation Test. 

This is the simplest and most important test to be made, for the reason 
that one of the piincipal functions of a transformer is its ability to thor- 
oughly and effectually insulate the secondary circuit from the primary 
circuit. 

Tests of the insulation of practically all high potential apparatus are now 
carried out by high pressure, rather than by test of the insulation resistance 
by galvanometer. Some insulations will show a very high test by galva- 
nometer, but will fail entirely under test with a voltage much exceeding that 
at which it is to be used. On the other hand, it is not uncommon to find 
insulation such that, while the galvanometer tests show low resistance, it 
will not break down at all under the ordinary voltages. For this reason, it 
is common practice among manufacturers of transformers to apply a mod- 
erately high voltage, from two to three times the working voltage, for a 
short period, usually about one minute. 

According to the Committee on Standardization of the A. I. E. E., the 
tests should be made with a sine wave of electromotive force, or where this 
is not available, at a voltage giving the same striking distance between 
needle points in air as a sine wave of the specified E.M.F., except where 
expressly specified otherwise. For needles, new sewing-machine needles 
should be used. It is recommended that the apparatus be shunted during 
test by the spark gap set for a voltage exceeding the required voltage by 
10 per cent. 

The committee also recommends the following voltages for use in 
testing : 

In electric circuits of rated voltage up to 500 volts. 

Apparatus of 10 k. w. capacity or less 1000 volts. 

Apparatus over 10 k. w. capacity 1500 " 

Of rated voltage over 500 but less than 1000 volts. 

Apparatus of 10 k. w. capacity and less 2000 volts. 

Apparatus over 10 k. w. capacity 3000 " 

Of 1000 and more but less than 2500 volts 5000 volts. 

" 2500 " " " " " 3500 "....... 7000 " 

" 2500 " " " " " 6600 " 10000 " 

" 6600 " " " " " 1| times rated voltage. 
In standard transformers these insulation tests should be (1) between pri- 
mary and secondary, and between primary and core and frame ; (2) between 
secondary and core and case. 

To obviate any induced potential strain, the secondary should be grounded 
while making the test between the primary and secondary, and between 
primary and core and case. 

In testing between the primary and secondary, or between the primary 
and core and frame, the secondary must be connected to the core and 
frame. 



374 



THE STATIC TRANSFORMER. 



It is also important that all primary leads should be connected together 
as well as all secondary leads, in order to secure throughout the winding a 
uniform potential strain during the test. 

Note. — See index for sparking-gap curve, and use new needles after every 
discharge. 

From one point of view, the factor of safety of the secondary need not be 
greater than that of the primary, and if 10,000 volts is considered a sufficient 
test for a 2000-volt primary, 1000 volts might be sufficient for a 200-volt sec- 
ondary. But a thin film of insulation may easily withstand a test of 1000 
volts, although it is so weak mechanically as to be dangerous. A 200-volt 
secondary should therefore be tested for at least 2500 volts in order to guar- 
antee it against breakdown due to mechanical weakness. 

The duration of the insulation test may vary somewhat with the magni- 
tude of the voltage applied to the transformer. If the test is a severe one, 
it should not be long continued ; for while the insulation may readily with- 
stand the momentary application of a voltage five or ten times the normal 
strain, yet continued application of the voltage may injure the insulation 
and permanently reduce its strength. 

Attention has been called to the fact that in testing between the primary 
and the core or the secondary, the secondary should be grounded. In test- 
ing between one winding and the core, for example, an induced potential 
strain is obtained between the core and the other winding which may be 




CONNECT CALIBRATING 
VOLTMETER BETWEEN 
A AND B 



04 OR 52 VOLT I 



Fig. 61. 

much greater than the strain to which the insulation is subjected under 
normal working conditions, and greater therefore than it is designed to 
withstand. In testing between the primary and the core, the induced po- 
tential between the secondary and the core may be several thousand volts, 
and the secondary may thus be broken down by an insulation test applied 
to the primary under conditions which do not exist in the natural use of 
the transformer. 

Attention is further called to the fact that during the test all primary 
leads as well as all secondary leads should be connected together. If only 
one terminal of the transformer winding is connected to the high potential 
transformer, the potential strain to which it is subjected may vary through- 
out the winding, and may even be very much greater at some point than at 
the terminals to which the voltage is applied. Under such conditions the 
reading of the static voltmeter affords no indication of the strain to which 
the winding is subjected. 

Indications which are best learned by experience reveal to the operator 
the character of the insulation under test. The transformer in test requires 
a charging current varying in magnitude with its size and design. From 
the reading of the ammeter, placed in the low potential circuit of the test- 
ing transformer, the charging current may be ascertained. It will increase 
as the voltage applied to the insulation is increased. 

If the insulation under test be good there will be no difficulty in bringing 
the potential up to the desired point by varying the rheostat. If the insula- 



TRANSFORMER TESTING. 



375 



tion be weak or defective, it will be impossible to obtain a bigb 
across it, and an excessive charging current will be indicated by the am- 
meter. 

Inability to obtain the desired potential across the insulation may be tbe 
result merely of large electrostatic capacity of tbe insulation and tbe conse- 
quent bigb charging current required, so that the high potential trans- 
former may not be large enough to supply this current at the voltage 
desired. 

A breakdown in the insulation will result in a drop in voltage indicated 
by the electrostatic voltmeter, an excessive charging current, and the burn- 
ing of the insulation if the discharge be continued for any length of time. 

Core Loss and Exciting- Current. 

In taking measurements of core loss and exciting current, the instruments 
required are a wattmeter, voltmeter, and ammeter. 

One of the two following described methods for connecting up the instru- 
ments is usually employed, although several others might be shown. These 
methods differ only in the way of connecting up the instruments, and are as 
follows : 

Method 1. — The voltmeter and pressure coil of the wattmeter are con- 
nected directly to the terminals of the test transformer. When the pressure 
of the voltmeter is at the standard voltage the reading of the wattmeter will 
be the core loss in watts. It is evident from an inspection of diagram 62 
that the wattmeter will indicate, in addition to the watts consumed by the 
test transformer, the I 2 R or copper loss in both the pressure coil of the 
wattmeter and voltmeter. This error, however, being constant for any 
pressure, is easily corrected. This method is very good for accurate results, 
and where the quantities to be measured are small it is most desirable. 



I s r — wvw 



*-*-» 




TEST TRANS 



Fig. 62. Core Loss (Method 1). 

Method 2. —The current coils of the wattmeter are inserted between 
a terminal of the test transformer and the terminal of the voltmeter and 
pressure coil of the wattmeter (see diagram 63). In this method the error 
introduced is the I 2 R loss in the current coil of the voltmeter. This is a 
very much smaller error than in Method 1, but does not allow of an easy or 
accurate correction, and the results obtained by it must, therefore, be taken 
without correction. For this reason Method 2 is more convenient, and for 
the measurement of large core losses, and for commercial purposes, it is 
sufficiently accurate. 




AMMETER WATTMETER TEST TRANS 



FlG. 63. Core Loss (Method 2). 
Core losses and exciting current should be measured from the low-poten- 
tial side of the transformer to avoid the introduction of high voltage in the 
test. 

If otes on Core Loss and Excitation Current. 

In an ordinary commercial transformer, a given core loss at 60 cycles may 
consist of 70 per cent hysteresis and 30 per cent eddy current loss, while at 
125 cycles the same transformer may have 55 per cent hysteresis loss and 45 
per cent eddy current loss. 



376 THE STATIC TRANSFORMER. 



The core loss is also dependent upon the wave form of the impressed 
E.M.F., a peaked wave giving somewhat lower core losses than a fiat wave. 
It is not uncommon to find alternators having such a peaked wave form 
that the core loss obtained, if the transformer is tested with current from 
them, will be 5 per cent to 10 per cent less than that obtained if the trans- 
former is tested from a generator giving a sine wave. On the other hand, 
generators are sometimes obtained which have a very flat wave form, so 
that the core loss obtained will be greater than that obtained from the use 
of a sine wave. 

The magnitude of the core loss depends also upon the temperature of the 
iron. Both the hysteresis and eddy current losses decrease slightly as the 
temperature of the iron increases. It is well known that if the tempera- 
ture be increased sufficiently, the hysteresis loss disappears almost entirely, 
and since the resistance of iron increases with the temperature the eddy 
current losses necessarily decrease. In commercial transformers, an in- 
crease in temperature of 40° C. will cause a decrease in core loss of from 5 
per cent to 10 per cent. An accurate statement of core loss thus necessi- 
tates that the temperature and wave form be specified. 

If, in the measurement of core loss, the product of impressed volts and 
excitation current exceeds twice the measured watts, there is reason to 
suspect poorly constructed magnetic joints or higher iron densities than are 
allowable in a well-designed transformer. 

Measurement of* Resistance. 

Resistance of the coils can be measured by either the Wheatstone Bridge 
or Fall of Potential Method. 

For resistances below one or two ohms it is generally more accurate to use 
the Fall of Potential Method. 

Resistances should always be corrected for temperature, common prac- 
tice being to correct to 20° centigrade. For pure soft-drawn copper this cor- 
rection is .4 % per degree centigrade. Readings should be taken at several 
different current values, and the average value of all the readings will be 
the one to use. (See Index for correction for rise of temperature.) 

Having obtained the resistance of the primary and secondary coils, the 
PR of both primary and secondary can be calculated ; the sum of the two 
being (very nearly) equal to the copper loss of the transformer. If it is 
preferred to measure the copper loss directly by wattmeter, then we must 
make test No. 4. 

The fall of potential method is subject to the following sources of error : 

(1) With the connections as ordinarily made the ammeter reading includes 
the current in the voltmeter, and in order to prevent appreciable error the 
resistance of the voltmeter must be much greater than that of the resistance 
to be measured. If the resistance of the voltmeter be 1000 times greater, an 
error of r x 5 of 1 per cent will be introduced, while a voltmeter resistance 100 
times the coil's resistance will mean the introduction of an error of 1 per 
cent. Correction of the ammeter reading obtained in (3) may thus become 
necessary, but whether or not it be essential will depend upon the accuracy 
desired. (See example below.) 

(2) The resistance of the voltmeter leads must not be sufficient to affect 
the reading of the voltmeter. 

(3) Since the resistance of copper changes rapidly with the temperature, 
the current used in the measurement should be small compared with the 
carrying capacity of the resistance, in order that the temperature may not 
change appreciably during the test. If a large current is necessary, read- 
ings must be taken quickly in order to obtain satisfactory results. If a 
gradual increase in drop across the resistance can be detected within the 
length of time taken for the test, it is evident that the current flowing 
through the resistance is heating it rapidly, and is too large to enable accu- 
rate measurement of resistance to be secured. 

It is quite possible to use a current of sufficient strength to heat the wind- 
ing so rapidly as to cause it to reach a constant hot resistance before the 
measurement is taken, thus introducing a large error in the results. Great 
care should be taken, therefore, in measuring resistance to avoid the use of 
more current than the resistance will carry without appreciable heating. 

(4) Considerable care is necessary to determine the temperature of the 
winding of the transformer. A thermometer placed on the outside of the 
winding indicates only the temperature of the exterior. The transformer 



TRANSFORMER TESTING. 



177' 



should be kept in a room of constant temperature for many hours in order 
that the windings may reach a uniform temperature throughout. The 
surface temperature may then be taken as indicative of that of the interior. 

i utpeilance and Copper-I^oss TT«»st. 

Method X. — In this method, which was first described by Dr. Sumpner, 
the secondary coil is short-circuited through an ammeter. A wattmeter 
and a voltmeter are connected up in the primary circuit in a manner similar 
to either of the two methods described for the core-loss test. An adjustable 
resistance or other means for varying the impressed voltage is placed in 
series with the primary circuit. 

To make the test, the voltage is raised gradually until the ammeter shows 
that normal full-load current is flowing through the secondary circuit. 
Readings are then taken on the wattmeter and voltmeter. 

This method of measuring the impedance and copper loss of a transformer 
is now seldom used, on account of the liability to error due to the insertion 
of the ammeter in the secondary. In addition to being inaccurate, it usu- 
ally requires an ammeter capable of measuring a very heavy current. 

Method 2. — This method differs from Method 1 only in that the sec- 
ondary is short-circuited directly on itself, an ammeter being inserted in the 
primary circuit. The diagram of connections is shown in Fig. 64. In con- 
necting up the voltmeter and the potential coil of the wattmeter, the same 
corrections hold as in the measurement of core loss and exciting current, 
and connections made according to whether accuracy of results or simplicity 
of test is the more imporant. 




Fig. 64. Impedance Test with Wattmeter. 
Having the readings of amperes, volts, and watts, we obtain from the 
first two the impedance of the transformer. This impedance is the geo- 
metrical sum of the resistance and reactance, and is expressed algebraically 
as follows : 

2=V J ff2 + (2 T »iZ) 8 » 
where z = Impedance, 
R= Resistance, 

L = Coefficient of self-induction, 
1= Current in amperes, 
n = Frequency in cycles per second, 
2n n L — reactance of the circuit. 

In a test on a transformer with secondary short-circuited as in Fig. 64 
above, and primary connected to 2000 volts, the impedance volts were 97 at 
full-load primary current of 2.5 amperes, then 
97 
Impedance = — = 38.8 ohms, 



and 



Impedance drop 



2.5 

97 X 100 
2000 



: 4.85 per cent. 



The reading on the wattmeter indicates the combined T" 2 /? of the primary 
and secondary coils, and in addition includes a very small core loss, which 
can be neglected, and an eddy current loss in the conductors. 

In standard lighting transformers, the impedance voltage varies from 
2 per cent to 8 per cent. In making this test, careful record of the fre- 
quency should be made, as the impedance voltage will vary very nearly 
with the frequency. 



o/ 



THE STATIC TRANSFORMER. 



Heat Vests. 

To test the transformer for its temperature rise, it is necessary to run it 
at full excitation and full-load current for a certain length of time. An 
eight-hour run at full load will usually raise the temperature to its highest 
point, and in the case of lighting transformers a full-load run very seldom 
continues longer than eight hours in practice. If it is desired to find just 
what is the final temperature rise under full load (as is often the case with 
transformers for power work) the transformer can be operated for two or 
three hours at an overload of about 25 %, after which the load should be 
reduced to normal, and the run continued as long as may be necessary. 

There are several methods for making heat runs of transformers, and all 
of them approximate the condition of the transformer in actual service. 

Heat Test, method 1. —The primary is connected to a circuit of 
the proper voltage and frequency, and the secondary loaded with lamps or 
resistance until full-load current is obtained. The temperature* of all acces- 
sible parts should be obtained by thermometer, and the temperature rise 
of the coils determined by increase of resistance. Frequent readings should 
be taken during the run to see to what extent the transformer is heating. 

Heat Test, method 3. — Where the transformer is of large size, or 
sufficient load is not obtainable, the motor generator method of heat test is 
preferable. Two transformers of the same voltage, capacity and frequency 
are required, and are connected up as shown in Fig v 65. 



TO 

CIRCUIT 

*'B" 









■0-1 



TO 
CIRCUIT 



this voltage to be approx. twice the 
impedance voltage of each transformer, 
jt..must be adjusted until full load 
current _flows in. transformers. 

Fig. 65. 



NOTE: 

THIS VOLTAGE TO BE THAT OF THE 

SECONDARY OF EACH 

TRANSFORMER 



The two secondaries are connected in parallel, and excited from circuit 
A at the proper voltage and frequency. The two primaries are connected 
in series in such a way as to oppose each other. 

The resultant voltage at B will be zero, however, because the voltage of 
the two primaries is equal and opposite. Any voltage impressed at B will 
thus cause a current to flow independent of the exciting voltages at the 
transformer terminals, and approximately twice the impedance voltage of 
one transformer will cause full-load current to flow through the primaries 
and secondaries of both transformers. 

The total energy thus required to run two transformers at full load is 
merely the losses in the iron and copper. Circuit A supplies the exciting 
current and core losses, and circuit B the full-load current and copper 
losses. 

Heat Test, method 3. —When only one transformer is to be tested, 
and this transformer is of large capacity, a modification of the motor gen- 
erator method can be used as described below : 

This method was first used in testing an 830 k.w. 25-cycle transformer made 
for the Carborundum Company of Niagara Falls. The connections are 
shown in Fig. 66. 

Both primary and secondary windings are divided into two parts, the pri- 
mary coils x and y being connected in multiple to the dynamo circuit, but 
an auxiliary transformer capable of adding a few per cent E.M.F. to that 
half of the primary is connected as shown in the y half. 



TRANSFORMER TESTING. 



379 



By this means the primary coils are properly magnetized, and full-load 
currents can be passed through them by varying the auxiliary E.M F. 

The two halves of the secondary coils are connected in series in opposi- 
tion to each other, and are subject to an auxiliary E.M.F. from the same 
generator, but reduced to the proper voltage by the auxiliary trans- 
former B. 

The currents were measured in all three transformer circuits, and the 
E.M.F. of one-half the secondary was measured. 

The method is accurate enough for large units, and is quite handy where 
no large dynamo can be gotten for supplying full-load currents, as in this 
case current is required only for the transformer losses and for supplying 
the auxiliary transformers. 



b 
aasssu 



a 

UAftASJ 



SECONDARY 



Fig. 66. 



General Electric Method of Testing One 
Large Transformer. 

Temperature Rise. 



To ascertain the temperature rise of the different parts of a transformer, 
thermometers are placed on the various parts, and readings taken at fre- 
quent intervals. These readings, however, indicate only the surface tern 
perature of a body and not the actual internal temperature. 

The average rise of temperature of the windings can be more accurately 
determined by means of the increase of resistance of the conductor, and 
is determined by knowing the resistances hot and cold. 
Let R e = resistance of one coil, cold. 

Rh = resistance of one coil, hot. 
T c =: temperature of one coil in cent, degrees, cold. 
Th = temperature of one coil in cent, degrees, hot. 
K=: temperature of coefficient of copper .004. 
_ J?fe(l + .0047 7 r) — Rr- 
h ~ .004 Re 

This equation is based on the assumption that the resistance of pure cop- 
per increases .4 % of its value at zero for every degree centigrade rise in 
temperature. 

If it be desired to know the temperature rise of both primary and second- 
ary coils, their hot and cold resistances must be determined separately ; but 
it is customary to determine the temperature rise by resistance of only one 
coil, usually the primary, and comparing the secondary temperatures by the 
thermometer measurements. The method for taking these measurements 
is described in the paragraph in this section on measurement of resistance. 

Ratio. 

As a check against possible mistakes in winding the coils and connecting 
up. a test should be made for ratio of voltages. 

The ratio test is made at a fractional part of the full voltage at no-load 
current, and should not be substituted for a regulation test. An error of one 
or two per cent is quite admissible in making this test, because of its being 
taken at partial voltages. 



380 



THE STATIC TRANSFORMER. 
Regulation. 






The regulation of a transformer can be determined either by direct meas- 
urement or by calculation from the measurements of resistance and reac- 
tance in the transformer. Since the regulation of any commercial trans- 
former is at the most but a few per cent of the impressed voltage, and as 
errors of observation are very liable to be fully one per cent, the direct 
method of measuring regulation is not at all reliable. 

Regulation B»y Direct Measurements. 

Connect up the transformer with a fully loaded secondary, as in Fig. 67. 
If the primary voltage is very steady, voltmeter No. 2 only will be neces- 
sary, but it is better to use one on the primary circuit also as shown. A 



H, 


"~i 


***** 


l 1 


***H 

LAMP LOAD 



Psrn 

I L|l!: 



Fig. 67. Test for Regulation of Transformer. 



reading of voltmeter No. 2 is taken with no load, and again with load, the 
difference in the two readings being the drop in voltage on the secondary. 
"We, therefore, have, 

/100 x reading at no loadx 
V Reading at full load. / 



Regulation = 100 



Regulation l»r Calculation. 

Several methods of calculating the regulation of transformers from the 
measurements of resistance and reactive drop have been devised. 

Below is a method by Mr. A. R. Everest, and recently published in the 
electrical journals, which has been found to answer the requirements of 
daily use. 

Let IR = Total resistance drop in transformer expressed as per cent of 
rated voltage. 
IX ■= Reactive drop, similarly expressed. 
P — Proportion of energy current in load or power factor of load. For 

non-inductive load Pr 1, 
W = Wattless factor of primary current. 

(With non-inductive load, W— Magnetizing current expressed as 
a fraction of full-load current. With inductive load, W— Watt- 
less component of load, plus magnetizing current.) 
Then if volts at secondary terminals = 100 %, 
Primary voltage — 
For Non-Inductive load. 

E — V(100+ PCR + WIX)* ± (/X)». 
For Inductive Loiid : 

E = V(ioo + PIR + wixy 4- {FIX + wm*. 

In each of these equations the last expression within parentheses repre- 
sents the drop " in quadrature." 



The magnetizing current = ^/ Exciting current — ( 



Core loss 2 
Voltage 



TRANSFORMER TESTING. 



381 



For frequencies of 60 cycles or higher, magnetizing current may be taken 
as 75 per cent of the exciting current. 

Extracting the square root in the expression for regulation may be 
avoided in the use of the following table : 



Quadrature Drop. 


Increase in Primary Voltage. 


2.5 per 

3 

3.5 " 


cent. 


.025 p 
.04 ' 
.06 ' 


er 


cent. 


4 

4.5 " 


" 


.08 ' 
.10 • 




<( 


5 

5.5 " 


" 


.13 ' 
.15 ' 




" 


6 

6.5 " 


(i 


.IS ' 
.21 ' 




" 


7.5 " 


" 


.24 ' 

.27 ' 




« 


8 

8.5 " 


« 


.31 ' 
.35 ' 




" 


9 " 
9.5 " 


" 


.39 ' 
.45 ' 




" 


10 " 


" 


.50 ' 


' 


" 



As an example, take a 2 k.w. transformer having the following losses : 
IR drop = 2%. 
IX drop =3.5%. 
Exciting current = 4 % or .04 ; then magnetizing current = 75% of this, or 
.03. 

1. IVon- Inductive load. — Secondary voltage = 100%. 

Primary voltage in phase = 100 + 2% + (.03 X 3.5%) = 102.1%. 

Quadrature drop = 3.5% ; this from table adds .06% of total primary volt- 
age =102.16%. 

2.16 
The drop is 2.16% of secondary voltage, or = 2.11% of primary voltage, 

which is the true regulation drop. 

2. Inductive Load. — With a power factor of .86, wattless factor of 
load = .5, and adding magnetizing current (which in most cases might be 
neglected on inductive load), W becomes .52. 

The primary voltage in phase is now 100% 4-2% X .86 + 3.5 X .52 -f- 103.18%. 
The quadrature drop is .86 X 3.5% X .52 X 2%-f 2.76%. 
From this table this adds .03. 
Primary voltage = 103.21%. 

3 21 
Regulation drop = ' = 3.11% of primary voltage. Regulation drop 

should always be expressed finally in terms of primary voltage. 

The above described methods of transformer testing are in use by one of 
the large manufacturers, and present average American shop practice. 

The following matter is largely from the important paper by Mr. Ford 
and presents the commonest theoretical test methods. 



&B2 the static transformer. 



EFIICIEKCY, 

The efficiency of a transformer is the ratio of its net power output to Its 
gross power input, the output being measured with non-inductive load. 
The power input includes the output together with the losses whieh are as 
follOWS : 

(1) The core loss, whieh is determined by test at the rated frequency and 
voltage. 

(2) The/-' A' loss of the primary and the secondary calculated from their 
resistances. 

Example. 
Transformer, Type II, 60 Cycles, 5 k.w., 1000-2000 Volts Prim., 100-200 
Volts Set'. 

AMPERES. 

Primary, at 2000 volts 2.6 

Secondary, at 200 volts 25 

Resistance. Ohms a.t20°O. 

Primary 10.1 

Secondary 0.067 

At Full Load, 

Losses. Watts. 

Primary /-A' ('>.'» 

Secondary PR -hi 

Total PM 105 

Core Loss 70 

Total Loss 17f> 

Output at Pull Load 5000 

input ' r>i7r> 

Efficiency 6000/5175 or 96.6% 

At Half Load. 

Losses. Watts. 

Total /-A' 26 

Core Loss 70 

Total Loss 96 

Output 25(H) 

Input 2596 

Efficiency 2500/2596 or 96.2% 

The all-day efficiency Of a transformer is the ratio of the output to the 
input during 24 hours.' The usual conditions of praotioewill he met if the 
calculation is based on 5 hours at full load, and 1!» hours at no load. 

Output. Watt Bes. 

5 Hours at Pull Load 25000 

l'.l Hours at No Load 

Total, 24 Hours 25000 

Input. 
5 Hours at Full Load 25876 

19 Hours at No Load (Neglecting /'-A Loss due 

to Excitation Current) 1330 

Total, 24 Hours 27205 

All-day Efficiency 25000/27205 or 91.9% 

In calculating the efficiencies in both of the above examples, the copper 
loss due to excitation current of the transformer has been neglected. This 
current, in the example given above, is less than 3%, and its effect on the 
loss of the transformer is thus negligible. Even at no load the total /'-' A 
loss Introduced by it is less than one watt. It is quite necessary, however, 
that the loss introduced hy the excitation current should he checked in all 
Oases. In some transformers, for example, the excitation current may 
reach 30% of the full-load current, and thus its effect is noticeable at large 
loads, while at \ load the loss in the primary winding due to excitation 
current is greater than the loss due to the load current. 



POLARITY. 383 



Inasmuch as the losses in the transformer are affected by the tempera- 
pure and the wave form of the E.M.F., the efficiency can be accurately 
specified only by reference to some definite temperature, such as 25° C, and 
by stating whether the K.M.F. is sine or otherwise. 

The foregoing method of calculating the efficiency neglects what are 
known as " load losses," i.e., the eddy current Josses in the iron ami the 
conductors caused by the current in the transformer windings. The watts 
measured in the impedance test include " load losses" and/ 2 R losses to- 
gether with a small core loss. Considering the core loss as negligible, the 
" load losses" are obtained by subtracting from the measured watts the PR 
loss calculated from the resistance of the transformer. It is sometimes 
assumed that the "load losses" in a transformer when it is working under 
full-load conditions are the same as those obtained with short-circuited 
secondary, and it is stated that these losses should enter into the calcula- 
tion of efficiency. Many tests have been made to determine whether or not 
the above assumption is correct, and while the results cannot be considered 
as conclusive, they indicate in every case that, under full-load conditions, 
the " load losses " are considerably less than those measured with short- 
circuited secondary. Inasmuch as these losses, in general, form a small 
percentage Of the total loss in a transformer, and in view of the difficulty 
iii determining them with accuracy, they may be neglected in the calcula- 
tion of efficiency for commercial purposes. The measurement of watts in 
the impedance test is, however, useful as a cheek on excessive eddy current 
losses in a poorly designed transformer. 

POLABIXY. 

Transformers are generally designed so that the instantaneous direction 
of flow of the current in certain selected leads is the same in all transform- 
ers of the same type. For example, referring to Fig. 08, the transformer 
there shown is designed so that the current at any in- 
y\ g stant Hows into the primary at A, and out of the sec- 

ondary at 0. Some such system is necessary, in order 
that transformers may run in parallel when similar pri- 
mary and secondary leads on different transformers are 
connected together. The test which is made to determine 
whether a given transformer is identical in this respect 
with other transformers of the same type is known as 
the polarity test. 

The polarity test should be unnecessary when banking 
transformers of the same type and design. When, how- 
ever, transformers manufactured by different companies 
are to be run in parallel, it is necessary to test them in 
second- I « order to avoid the possibility of connecting them in 

I ary I such a way as to short circuit the one on the other. 

c D Their polarity may be determined by one of the follow- 

FlG. G8. ing methods. 

In Fig. 68 primary lead A should be of the same po- 
larity as the second lead 0. Connect the primary lead Y> to the second- 
ary lead C. Apply 100 volts, say, to the primary AB of the transformer. 
The voltage measured from A to I> should be greater than the applied volt- 
age if the transformer is of the correct polarity. In other words, a trans- 
former connected as shown should act as a booster to the voltage. If the 
leads A and C are not of the same polarity, the voltage measured from A to 
1) should be less than that applied at AB. 

If a standard transformer, known to have correct polarity and the same 
ratio as the test transformer, is available, the simplest method for testing 
the polarity is to connect the primaries and secondaries of the transformer 
in parallel, placing a fuse in series with the secondaries. On applying volt- 
age to the primaries of the transformers, if they an; of the same polarity 
and ratio, no current should flow in the secondary circuit, and the fuse will 
remain intact. If the transformers are of opposite polarity, the connection 
will short circuit the one transformer on the other, and the fuse selected 
should therefore be small enough to blow before the transformers are 
injured. 

In nearly all transformers there will be a slight current in the secondaries 
when connected as above. This current is known as the exchange current, 
and should be less than 1% of the normal full-load current of the trans- 
former. 



u 



384 



THE STATIC TRANSFORMER. 



DATA TO BE GftETEIKJI f.\EI» BY TESTS. 
Partly from a paper by Arthur Hillyer Ford, B. S. 
Copper loss, to determine the efficiency. 



Iron-core loss, hot and cold, to determine the efficiency : to separate 
the hysteresis from the foucault current loss. 
If W = watts output, 

1 = watts iron-core loss, 
C= watts copper loss, 
then the 

Efficiency = 100 - f ^ T J g X 100 ) 

Foucault currents loss should decrease with an increase in tempera- 
ture. 
Hysteresis loss is supposed to be constant regardless of heat. 
III. Open circuit or exciting current. 
IV". Regulation, to determine the magnetic leakage. 
V. Rise in temperature in case and out of case, for no load and full 
load ; with and without oil. 
VI. Insulation. 

Methods. 
Opposition Method of Ayrton and Sumpner. — This method 
is especially valuable where the transformers to be tested are of large ca- 
pacity, and a source of power great enough to put them under full load in 
the ordinary way is unavailable. A supply of current of an amount some- 
what greater than the total losses of both transformers is all that is neces- 
sary. Following is a diagram of the connections, by which it will be seen 
that the transformers ai'e so connected that one feeds the other, or they 
work in opposition. 




— / wwvw 



'TMMOTfflRF^ 




FROM SOURCE 

OF CURRENT 

100-VOLT8 — 



Fig. 69. Diagrams of Connections for Ayrton 
and Sumpner Opposition Method of Testing 
Transformers. 
In making the test, current is turned on and the resistance R adjusted 
until full-load current flows in the secondary, as shown by the ammeter A, 
and the primary current and voltage in A and V is up to standard. Then 
the watts read on W are equal to the iron losses in both transformers, and 
W, the losses in the copper of the transformers plus the copper loss in the 
leads and in the current coils of W, and A. 



DATA BY TESTS. 



385 



The total loss in both transformers is watts loss = "W -f- W, — a, where a 
is the loss in the leads and instruments which may be calculated by 1 2 R. 

Method of Dr. §umpner. Iron JLoss. — The following diagram 
shows the connections for Dr. Sumpner's test for iron losses. The low- 
pressure side is connected to a source of current of the same pressure at 
which the transformer is expected to work, thus producing the same pri- 
mary voltage in the high-pressure side at which it is expected to work. 
With the primary circuit open, the iron losses in the transformer are read 
directly in watts on the wattmeter. 



ADJUSTABLE 
RESISTANCE 



,'n 


§ 




£ 


o 




1 

f 


g 



s ■ AAA/ 


R. T CO 

O a, 

I 







Fig. 70. Dr. Sumpner's Test for Iron Losses. 

Copper Loss. — The next diagram shows the connections for determin- 
ing the copper losses. The low-pressure side is short-circuited through an 
ammeter, the high-pressure side being connected to the 100-volt supply- 
mains. The resistance K. is then adjusted to obtain full-load or any other 
desired current in the secondary, as shown by the ammeter. The reading 
of the wattmeter will then show the total copper losses in the transformer 
and in the ammeter plus a very small and entirely negligible iron loss. The 
ammeter losses and that in the leads may be calculated by l 2 B. The small 
iron loss can be separated or determined by disconnecting the ammeter and 
adjusting R until the pressure on the primary is the same as in the copper- 
loss test : the wattmeter will then show the small iron loss. 




Fig. 71. Dr. Sumpner's Test for Copper Losses. 

The iron loss is proportional to (ft 1,6 and (ft, the magnetic density is pro- 
portional to the pressure at the terminals of the transformer, therefore the 
iron loss is equal to A'.(ft 1,b where K is a constant and (ft the voltage. In the 
iron-loss test the (ft = 1000 and in the copper-loss test 
(ft = 100. 

K X 1000 1 - 6 = 63,000 K 

K x 100'- fi — 1,600 K = 2.5 % of total iron loss. 

Heating. — Tests should be made at no load, at full load, and at inter- 
mediate loads for rise of temperature of the transformers out of their cases, 
in their cases, without oil and with oil, if full data is wanted. If a strictly 
commercial test is all that is necessary, a test with the transformer at full 
load and set up in the condition it is to be run, will be sufficient. 

Surface temperatures can be taken by thermometers laid on and covered 
with cotton waste. In oil-insulated transformers the temperature of the 
oil should be taken in two places, — inside the coil, and between the coil 
and case. 

I^eakasre Drop= — The drop in the secondary due to magnetic leakage 
can be found by deducting from the measured total drop the I 2 R drop due 
to the resistance of the coil. 



ELECTRIC LIGHTING. 

1.14; HT. 

Velocity of light approximately 192,000 miles per second. 
Composition of Sunlig-ht. 



Violet, the maximum chemical ray. 

Indigo. Blue. 

Yellow, the maximum light ray. 

Orange. 

Red, the maximum heat ray. 



Green. 



Primary. 

Secondary. 

Tertiary. 



Red, 

Orange, 

Brown, 



Colors. 

Yellow, 
Purple, 
Gray, 



Blue. 
Green. 
Broken green. 



Intensity of Illumination on a surface is inversely as the square 
of the distance between the surface and the source of light. 



Intensity rr 



Quantity of light 



Intensity 



4n- X distance* 
If light strikes the surface obliquely, 
then 

Quantity X Cos. i 
in x distance 2 

Where i is the angle of incidence, or the angle which the rays make with 
the normal to the surface. 

Intensity of lig-ht in a given direction is proportional to the cosine of 
the angle, the direction and the normal to the element of the luminous sur- 
face from which the light is emitted. 

Trotter gives in the following table the intensities of different sources of 
light. 

Intensities of Different Sources of Iag*lit. 

(Trotter.) 



C. P. per Sq. In. C.P. per Sq.C 



Red. Green. 



Red. Green. 



Platinum (Yiolle standard) 

Sun's disk 

Sky, near sun 

Albo carbon on edge 

White paper, horizontal, exposed to sum- 
mer sky, noon 

White paper, sun 60° high, paper facing 
sun 

Albo carbon, flat 

Argand 

Black velvet, summer sky, noon .... 

White paper, reading without straining . 

386 



120 

487.000 
120 
73.5 

16.5 

8.25 
10.5 
6.8 

0.0333 
0.0018 



120 

1000000 
120 
60.7 

35.2 

17.2 
8.7 
5.24 
0-07 
0.0024 



18.5 
75.500 
18.5 
11.4 

2.56 

1.28 

1.63 

1.05 

0.0052 

0.00028 



18.5 
155,000 
18.5 
9.4 

5.45 

2.67 

1.35 

0.82 

0.0109 

0.0003 



LIGHT. 387 

Intensities of Different Sources of Iiig-ht — Continued. 



Sperm candle = 

Moon, 35° above horizon 

Moon, high , 

Bats wing (whole flame) 

Methven standard 

Incandescent carbon filament (glow lamp 
Crater of electric arc 



White. 



2 


0.31 


2 


0.31 


3 


0.46 


2.25 


0.35 


4.3 


0.666 


120 


18.5 


45,000 


7,000 



White. 



Iflean Spherical Intensity is the intensity which the light from the 
given source would have at unit distance, if it radiated uniformly in all 
directions, the total quantity remaining unchanged. 

Units of JLig-ht. 

The quantity of lig-ht emitted from any source of light is expressed 
in terms of that of some specified standard of reference. 

No very satisfactory standard for all purposes has as yet been selected, 
but those listed below are among the best in use or proposed. 

a. The British standard candle, a spermaceti candle seven-eights of an 
inch in diameter, weighing one-sixth pound, and burning at the rate of 120 
grains per hour. A rough and ready standard, not very accurate. 

b. The French stearine candle weighs one-fifth pound, and burns at the 
rate of 117.3 grains per hour, giving a light equivalent to 1 to 1.4 British 
candles, and is equally unsatisfactory and inaccurate. 

c. The Methven screen, an Argand burner of 16 candle-power, before which 
is placed a screen having a small rectangular aperture so placed in the 
screen in relation to the position of the flame that the light passing through 
equals two British candles. Methven claims the amount of light passing 
through the aperture is not affected by quality of the gas if the flame is kept 
at a constant height. The value of this standard is questioned by some 
authorities. 

d. The Harcourt pentane air-gas lamp, burning a mixture of 576 volumes 
of air to one of liquid pentane, or 20 volumes of air to seven of pentane gas 
— at 60° F., is very satisfactory when carefully protected from draughts of 
air. 

The height of flame is 1\ inches and diameter of burner \ inch, the light 
being equivalent to one British candle. 

e. The Carcel lamp, the principal French standard, equals 9^ British can- 
dles, and burns 42 grammes of purified colza oil per hour, the flame being 40 
mm. high. MM. Regnault and Dumas have proven by experiments that 
when the consumption of colza is at a rate between 40 and 44 grammes per 
hour, the light emitted by this standard is proportional to the weight of 
colza burned. Following is a table showing the proper dimensions of this 
standard. 



Dimensions of Carcel Lamp. 



External diameter of burner 

Interior diameter of inner air current . . 
Interior diameter of outer air current . . 

Total height of chimney 

Distance from elbow to base of glass . . . 
Exterior diameter at level of bend .... 
Interior diameter of glass at top of chimney 
Mean thickness of glass 



23.5 
17.0 
45.5 
290 
61 
47 
34 
2 



)88 ELECTRIC LIGHTING. 



' 



LTse lighthouse wick weighing 3.6 grammes per decimeter and woven with 
75 strands. This standard is quite satisfactory if carefully used. 

/. The Amy I- Acetate-lamp is substantially a well designed spirit lamp 
having a flame 40 mm. high, and gives a light equal to one British candle. 
This is quite a satisfactory standard for a simple one. 

g. The platinum standard proposed by MM. Cornu and Violle is the light 
emitted by one square centimeter of platinum at its melting-point. Violle 
shows that the light emitted by this unit is equivalent to ldh to 19| British 
candles, and experiments by Prof. C. R. Cross show that the" light emitted 
by various specimens of platinum at the melting-point, is quite constant 
for a wire of definite dimensions. This standard is highly thought of by 
scientists. 



Tlie surface ilium iuation is the quantity of light received by the 
surface of a body per unit of surface from a standard source and at a defi- 
nite distance from it. Sir. W. H. Preece has proposed to give to the unit of 
surface illumination the name of lux, which would mean the quantity of 
light received by a square foot of surface from one carcel at a distance of one 
meter. 

By this standard one 10 c.p. lamp would give a surface illumination of one 
lux at a distance of 4 ft. 2| in., and 1000 c.p. lamps would give a surface illu- 
mination of a lux at a distance of 33 ft. 5| in. 

The Director of the Central Laboratory of Electricity of Paris, M. de 
Nerville, has employed for the measurement of surface illumination a unit 
called the bougie-meter, the bougie being one-tenth of a carcel, and equiva- 
lent to one British candle at a distance of 3.34 feet. This is a convenient 
standard. 



German Standard's. — The standard German candle is made of paraf- 
fine after an elaborate specification, and is used to some extent in approxi- 
mate work. Its flame is somewhat longer than that of the English candle, 
being some two inches in height for the standard, and is about 10% more 
powerful. 

The legal standard in Germany is the so called Hefner unit, which is the 
light given by the amylacetate lamp mentioned on the previous page. This 
lamp lias been exhaustively investigated by the Reichanstalt, which fur- 
nishes certified tested standard lamps, making this unit more nearly an 
international standard than any of the others named ; its intensity is 
about 10% less than that of the English candle, and its normal flame is 40 Mil- 
imeters high. It is very steady, and owing to the fact that lamps of certified 
value can be so readily obtained it is widely used not only in Germany but 
elsewhere. Careful instructions are issued with each lamp, and when used 
in accordance with these instructions the errors of measurement are not 
more than half those met with in the use of standard candles. The color is 
somewhat against this unit, being a distinctly reddish orange, which is a 
rather serious objection when used as a working standard in measurements 
of Welsbach burners or incandescent and Nernst lamps. Even with its 
faults though, it is probably the best primary standard that we have, as it 
can be reproduced accurately to a most unusual degree. 

As photometry is perhaps more generally practiced in connection with 
incandescent electric lamps than with any other source of light, it is only 
natural that the incandescent lamp should have come into very general 
use as a secondary standard ; and it is probable that a well seasoned incan- 
descent lamp makes the very best and most reliable standard for this pur- 
pose that can be found. Care must be taken that the filament is not worked 
at too high a temperature, and that it is aged by several hundred hours of 
preliminary burning before being used as a standard. When burned at a 
fixed and uniform voltage, comparison with a good primary standard will 
determine its intensity, which Avill remain very nearly uniform if carefully 
used, its only change "being a small and perfectly ascertainable decrement 
with time. Various attempts have been made to use an incandescent lamp 
of special design as a primary standard, but so far the results have not been 
at all satisfactory. 



LIGHT. 



389 



Following is a table which shows the comparative value of the various 
primary standards : 





Bougie- 
meter. 


Carcel. 


Hefner 
unit. 


German 
candle. 


English 
candle. 


French 
candle. 


Bougie-meter . . . 

Carcel 

Hefner unit .... 
German candle . . 
English candle . . 
French candle . . . 


1. 
9.6 
0.88 
1.05 


0.104 

1. 

0.92 

0.109 

0.104 

0.145 


1.13 
10.9 
1. 

1.23 
1.099 
1.538 


0.955 

9.20 

0.815 

1. 

0.915 

1.281 


0.97 

9.6 

0.91 

1.09 

1. 

1.40 


7.00 

0.65 

0.78 

0.714 

1. 



Measurement of Intensity of J^igvht. 

The instrument used for determining the- relative intensities of lights is 
called a photometer ; following is a list of some of the jbetter types, with a 
short explanation of their principles. 




Fig. 1. Portable Bunsen Photometer. 

In all types let the following symbols mean the same. 

i = intensity of one light at the distance d . 
i t = intensity of the other light at the distance d, 



390 



ELECTRIC LIGHTING. 



Ruiu ford's photometer compares the shadows of an opaque rod thrown 
on a white screen by two lights. 
When the shadows are of equal density, 
i _ d* 
i 3 — d*' 
In Runsen's photometer a piece of white paper, blotting-paper is good, 
with a grease spot in its center, is placed between the two lights, with its 
surface at right angles to the line of the rays ; moving the paper back and 
forth between the lights until the grease spot disappears ; then the two 
lights are to each other as the squares of the distances between each and the 
screen : or 

* _ d 2 

k~~d\ 2 ' 

If the lamp under test be at a height h above the horizontal plane of the 
photometer and standard lamp or candle, other symbols remaining the 
same, and the standard be one c.p., then 



c.p. of the lamp 



_ (h* + d,^ 



rf 2 X d x 

In Ritchie's photometer tAvo equal white surfaces are placed at an 
angle with each other, and with the line of light and their brightness com- 
pared, moving back and forth on the line of light until both surfaces are 
alike in illumination ; the relative intensities of the lights are then the 
same as with the Bunsen instrument. 




Fig. 2. Prof. L. Weber's Portable Photometer. 



.ijrton and Terry use what they call a dispersion photometer, in 
which a concave lens is used in the path of the stronger light to reduce its 
intensity by dispersion of its rays to a known degree. 

This instrument is useful in measuring arc lamps. 

Sabine's wedge photometer reduces the stronger light a known degree 
by passing it through a medium of neutral tinted glass, which also allows 
of the colored rays being compared. 

In Jolv* photometer, tAvo slabs of paraffin Avax, or translucent glass about 
g// x 2" x y> % are fastened together back to back by Canada balsam, a sheet 



LIGHT. 



391 



of paper or silver foil being first interposed, after which the edges and sur- 
faces are ground smooth. 

This slab is placed between the two lights, with the plane of the joint at 
right angles to the line between the lights, and moved back and forth on 
that line until the observer looking at the edge of the slab finds both sides 
equally illuminated, when the relative intensities are as before. By revers- 
ing the slab, a check can be had on the observation. 

Prof. Iu Weber has invented one of the handiest and most accurate 
photometers, description of which follows. 

The apparatus consists of a tube, A, about 30 cm. long, which can be moved 
up and down and swung in a horizontal plane on the upright, c. The stand- 
ard light, S, a benzine lamp, is contained in a lantern fastened to the right 
end of the tube, A. Within the tube, A, a circular plate of opal glass can be 
moved from or towards the light, S ; its distance from E is read in centi- 
meters on the scale, s, by means of an index fastened to the pinion, P. At 
right angles to tube, A, a second tube, B, is fastened. This tube can be 
rotated in a vertical plane, and its position in reference to the horizontal 




Fig. 3. 

is read on the graduated circle, C. A rectangular prism contained in tube 
B in its axis of rotation receives light from the opal glass plate in tube A, 
and reflects this light towards the eye-piece, O, so that the right half of the 
field of vision is illuminated by this light, the left half is illuminated by the 
light entering the tube, B, through g. 

In making measurements, the tube B is pointed toward the source of 
light to be measured. The light has to pass through a square box, g, in 
which may be inserted one or more opal glass plates, in order to diminish 
the intensity of the light, and thus to make it comparable with the standard 
light. The apparatus permits the measurement of light in the shape of a 
flame, as well as the measurement of diffused light. 

Since the measurement of diffused light interests us most at present, a 
short description of the method will not be out of place. 

A white screen, the surface of which is absolutely without luster, fur- 
nished as part of the apparatus, is placed in a convenient position, either hor- 
izontal or vertical, or at any desired inclination, toward the source of light. 

The photometer having been located at a convenient distance from the 
screen, the tube B is pointed to the center of the screen. The distance of 
the phonometer from the screen can be varied within very wide limits, the 
only restrictions being that the field of vision receives no other light than 
that emanating from the screen. The necessary precautions for adjustment 
having been observed, the opal glass plate in the tube A is moved until both 
halves of the field of vision appear equally illuminated. The distance, r, of 
this glass plate from the standard light at the moment of equal illumina- 



392 



ELECTRIC LIGHTING. 



tion is read on the scale on tube A in millimeters, and the intensity of 
illumination on the white screen is calculated from the formula, 



10000 



K. 



The constant A' is previously determined as follows : 

A standard candle is placed exactly one meter distant from the white 
screen, and the tube, B, of the photometer is pointed towards the screen, so 
that the center of the screen, which is marked by a cross, is seen in the 
center of the field of vision. As indicated in Fig. 3, the photometer must be 
so placed that the eye looking through the eye-piece, sees nothing but the 
white screen. The angle of inclination under which the screen is obseiwed 
may be varied within wide limits without influencing the result ; it should, 
however, not exceed 60 degrees from the normal to the screen. 

Equal illumination of both halves of the field of vision having been ob- 
tained by means of adjusting the opal glass plate in tube A, the constant, K, 
is found by calculation ; 

r 2 



K = 



E* 



Since r is read in millimeters, and It is made 1 meter or 10000 millimeters, 
10000 instead of 1 must be taken in the formula for calculating the intensity 
of illuminating in meter candles. 

A second method permits of measurements of diffused light without the 
intervention of a screen ; but for further details the reader is referred to the 
description of the apparatus by Professor Weber, Elekrotechnische Zeit- 
schrift, vol. v., p. 166. 

Since the whole apparatus can easily be taken apart, and packed in a box 
about 24x8x12 inches, it recommends itself extremely well for out-of-door 
work. In this case the benzine lamp might well be replaced by a small in- 
candescent lamp, provided this lamp is standardized before and after each 
set of experiments. Such miniature lamps been have found very con- 
venient, and quite sufficiently constant in candle-power for several hundred 
observations. 

In the iMinmer-Brouiliain photometer, cut of the carriage of which is 
shown below, the rays of light from the two sources under comparison enter 
at the sides so as to strike the surfaces of the opaque gypsum screen. Dif- 
fused light from these white surfaces reaches two parallel mirrors (inside) 
at an angle of 45°, and is reflected to right angled prisms which have the 
outer portions of their hypothenuse surfaces cut away and coated with as- 
phalt varnish to secure complete absorption. Light entering the prisms 
from the mirrors is either transmitted or totally reflected at their surface of 
contact, so that an observer at the telescope tube sees a circular disk of light 




Fig. 4. Lummer-Brodhun Photometer Carriage. 



LIGHT. 



393 



from one side of the gypsum screen surrounded by an annular ring of light 
from the other side, the boundary line between the two being sharply defined. 
The sensibility of this instrument as proved both theoretically and prac- 
tically, is between three and four times that of the Bunsen grease spot. 

Illuminating- Power for internal lighting varies according to the 
nature and color of the walls and objects inside of the room. Dark walls 
require more lighting than light walls. Dr. Sumpner finds that dull walls 
only reflect about 20 per cent of the light incident upon them, whilst ordi- 
nary tints reflect 40 to 50 per cent, clean white surfaces 80 per cent, ordinary 
mirrors 80 per cent, and very good mirrors 90 per cent. Hence well-whitened 
rooms require only one-fifth of the light required with dull walls. The 
amount of light also depends upon the height of the room. In rooms about 
10 ft. high, a 16-c.p. lamp placed 8 ft. from the floor gives 1 candle-foot on 
the table and \ candle-foot on the floor. The following table may be used 
as a rough guide, subject to the above conditions : 



No. of 16-c.p, Lamps 
per 100 Square Feet. 



1 
1.5 

2 
3 

4 



No. of Watts per sq. 
ft. if 16-c.p. Lamp 
Takes 50 Watts. 



0.5 
0.75 
1.0 
1.5 
2.0 



Approximate Effect. 



Dull. 

Medium. 

Good. 

Bright. 

Brilliant. 



Foree Bain gives the following table for number of incandescent lamps 
required for good illumination : 



Dimensions of Rooms in Feet. 


Number of 

Lamps, Each 

8 to 10 Can- 


Height of Lamps 
above Floor. 












Length. 


Width. 


Height. 


dle-powers. 


Feet. 


Inches. 


15 


15 


12 


2 to 3 


6 


9 


18 


18 


15.1 


5 " 6 


7 





24.6 


24.6 


17 


9 " 12 


8 


1 


33 


33 


22.5 


16 " 20 


2 


3 


40 


40 


30 


25 " 30 


11 


4 


65 


65 


45 


40 " 50 


13 


2 


72 


72 


50 


100 " 120 


18 


6 



With 16 candle-power lamps 75 per cent, and with 20 candle-power lamps 
65 per cent of the above numbers will give equal illumination. 

ARC lAMPi. 

In the LTnited States, arc lamps may be classed somewhat as follows : 



Continuous Current Arc Lamps. 

ILow Potential, high current, using about 20 volts across the termi- 
nals, and 30 amperes of current ; formerly largely in use ; now no longer 
manufactured. 



394 



ELECTRIC LIGHTING. 



High Potential : using 45 to 60 volts and 9.6 to 10 amperes for a nomi- 
nal 2000-c.p. standard lamp. This lamp is more used than any other for 
street lighting, and with the 1200-c.p. lamp, so called, taking 6.8 amperes 
and 45 to 50 volts, includes the larger part of all arc lighting in the United 
States. 

Inclosed Arc, taking 5 amperes and about 80 volts ; this lamp is now 
much used, as it needs recarboning but about once a week (100 to 150 hours). 

The first of the three classes of arc lamps mentioned above is no longer in 
use except on old circuits, but is always connected in series on constant 
current dynamos. 

The hig-h potential and inclosed arc lamps are connected in 
series on constant current dynamos ; and with some slight difference in 
mechanism are also connected to constant potential circuits. 



Alternating' Current Arc lamps. 

Alternating current arc lamps are made in great variety, and average 
about 15 amperes for the 2000-c.p. arc, at 28 or 30 volts, but require about 
35 volts to start promptly ; and are made for series or parallel circuits. 

They are used largely on constant potential circuits in connection 
with the regular transformer, or in connection with specially-designed 
series transformers or regulators, for the description of which see chap- 
ter on " Transformers." Owing to the reactive effect of these lamps, 
they can be run one lamp across the terminals of a 100-volt circuit. 
Some types use a resistance, others use a compensating coil, and still 
others are so designed as to the actuating magnets as to require no extra 
reactance in series with the lamp across a 100 or 104 or 110 volt constant 
potential circuit. 

The Westinghouse Electric and Mfg. Co. and others use, where required, 
what is called an " economy coil," which is something like a small trans- 
former placed across the terminals of a 100-volt a,c. circuit. 

Three a.c. arc lamps can be connected to the terminals of this coil and if 
one lamp goes out, the current drops in the main, bnt keeps automatically 
the same in each remaining lamp circuit, as the coil cot in use on a lamp 
assists the adjacent coils. Following is a diagram of the arrangement. 




curan 

ioo v. L 



A 14. AMPERES 



Fig. 5. 



The Inclosed Arc lamp is the only radical change in arc lamp 
practice during a number of years past, and is now being used for a great 
part of all new work installed. 

It has been found that by inclosing the tips of the carbons in a small 
receptacle more or less approaching air-tight conditions, that combustion 
of the carbons is practically complete, leaving no dust, and takes place at a 
much slower rate, burning with the ordinary 12" x \" carbons from 50 to 150 
hours continuously, according to the design of the lamp. The potential at 
the arc is 75 or 80 volts, and according to the best modern practice the cur- 
rent used is from 4.5 to 6 amperes. With this high voltage it is usual to 
place an adjustable resistance in the top of the lamp, or near by, and one 
lamp can then be connected directly across constant potential circuits of 
100 to 125 volts. 

Although there may be some question as to the lighting efficiency of the 
inclosed arc, the very great advantages from carbon economy and infer- 
quent trimming, as well as lack of dirt from carbon dust, render it very 
desirable in practical use. 



ARC LAMPS. 391 



As the upper carbon stump can often be used as the lower when retrim- 
ming, ordinary commercial lamps will require trimming not oftener than 
once a month. 

The safety of inclosed arcs appeals strongly to the underwriters, who 
have no fear of sparks floating away from them to set goods afire in shops 
and factories. 

As the consumption of carbon is so slow, the feeding mechanism can be 
very simple and the feed very regular, and if in addition to this a good 
quality of carbon be used, the light is extremely steady and of the very best 
quality. 

If care is taken in selecting the globes, shadows of frame and arc can be 
reduced to the last degree. 

methods of Meg-iilation in Arc lamp* may be classified as 
follows : — 

Carbons lifted or separated by direct or main magnet ; shunt magnet 
acting on a variable resistance to cut out the main magnet in feeding. 

Carbons lifted by main magnet as before, and shunt acting to put the main 
magnet (made movable) into position for feeding. 

Carbons separated by main magnet armature ; shunt circuiting magnet 
acting to divert or shunt the magnetism of the main magnet from its arma- 
ture. 

Carbons separated by main magnet and shunt acting to free the carbon- 
holder, independently 6f the support given by the main magnet. 

Carbons separated by a spring allowed to act by the main magnet lifting a 
weight which otherwise holds the spring from acting ; shunt magnet acts 
against the spring, to feed and regulate the length of arc. 

One carbon, generally the lower, separated by main magnet, while the 
other holder is released for feeding only, such feeding being under the con- 
trol either of a differential system or a shunt magnet only. 

Carbons separated by main magnet, which lifts the shunt and its armature 
together, Avhile the shunt magnet armature, acting on the feeding mechan- 
ism, controls the arc and feed of the carbons. 

Carbon feeding mechanism independently attached to main magnet arma- 
ture and to shunt armature so as to receive opposite movements of separa- 
tion, and feed from each respectively. 

Carbons separated by a feeding mechanism moved by the main magnet, 
and fed by a further movement of said mechanism, causing release or re- 
turn of same under the accumulated force of both shunt and main magnets, 
acting in the same direction. 

Differential clock gear for separation and feed of carbons under control 
of the regulating magnet system, either simple or differential. Some of the 
older clockwork lamps embodied this principle. 

Carbons controlled by armature of a small electric motor under control of 
a differential field which turns the armature in one direction for separating 
and in the other or reversed direction for feeding the carbons. 

Carbons controlled by a motor running at a certain speed when the arc is 
of normal length, and varying in speed when the arc is too short or too long, 
combined with a centrifugal governor on the shaft of the motor, acting on 
variations of speed to gear motor shaft to screw carbons together or apart, 
as needed to maintain the normal arc. This mechanism has been applied 
to large arc lamps, such as naval search-lights, and has the advantage of 
great positiveness, and an ability to handle heavy mechanism. 

There are also a considerable number of modifications of these principles. 

Searchlight Projectors and focusing lamps for theatrical use and 
for photo-engraving, etc., take large and varied quantities of current, as 
they are always connected across the terminals of constant potential cir- 
cuits, with a regulating resistance in series with the lamp. The General 
Electric Company state in one of their bulletins the following as being the 
approximate currents taken by the different sizes of searchlights : 
Diam. of Projector. Amperes. 

12 inch 18 to 20 

18 " 30 " 35 

24 " 50 " 60 

30 " 75 " 90 

36 " 90 " 100 

60 " 125 " 150 



396 ELECTRIC LIGHTING. 



Tests for Arc JLig-lit Carbons. 

For Open Arcs. 

The satisfactory working of arc lamps is largely dependent upon the 
quality of the carbons used. If carbons are made of impure materials, they 
will jump and flame badly. If not baked properly, they may cause annoy- 
ance by excessive hissing or flaming, or become too hot because of high 
resistance. If the material of which they are made has not been properly 
prepared in its preliminary stages, the carbons will have either too short a 
life, through giving a good quantity and quality of light, or will have good 
life, but will burn with an excessive amount of violet rays, hence with poor 
illumination. 

Eor indoor use a free-burning, uncoated carbon of medium life should 
be used, so as to give a good quality and quantity of light. If longer life is 
desired they may be lightly coated with copper without materially interfer- 
ing with the light. (About 1£ lbs. to 2 lbs. of copper per thousand, A" x 12" 
carbons, and a half pound more for £" x 12" carbons will give good results, 
increasing the life from an hour to an hour and a half.) 

For out-door use a more refractory burning carbon may be used to advan- 
tage, giving a longer life, as the quality of the light is not so important. 
Copper-coated carbons are also usually employed, and may have about four 
pounds ot copper per thousand for j 7 B " x 12" carbons, aiid five pounds for 
A" x 12". Other sizes in proportion. 

All plain molded carbons, and most of the forced carbons, deposit dust 
when burned in the open arc. Those depositing the most dust give out the 
most light, but have the least life. Those depositing the least dust usually 
have the longest life, but the light is of inferior quality on account of the 
increase in the proportion of violet rays. 

The quality of any carbon may be very quickly tested in any station by 
using the following method, which has been largely employed by carbon 
manufacturers . 

The important points to be determined are therangre, including the hiss- 
ing, jumping, and flaming points, the resistance, and the life. 

The Itang-e is found by trimming a lamp with the carbons to be tested, 
allowing them to burn co good points and the lamps to become thoroughly 
heated; then connect a voltmeter across the lamp terminals, and very 
slowly and steadily depress the upper carbon until the lamp hisses, when 
the voltage will make a sudden drop. This is called the Hissing-Point, 
and varies according to the temper of the carbon. It should be between 40 
and 45 volts — preferably 42 volts. Then lengthen the arc somewhat, and 
allow it to become longer by the burning away of the carbons. Presently 
the arc will make small jumps or sputters out of the crater in the upper 
carbon. This is the «Funining--Point, and should be not less than 58 or 
60 volts. Let the arc still increase in length, carefully Avatching the volt- 
age, and in most carbons there will soon be a decided "flaming. This is the 
flaming'-Poiiit. This should not be less than 62 to 65 volts. Very im- 
pure carbons will commence to jump and flame almost as soon as the volt- 
age is raised above the hissing-point, and even the hissing-point in such 
cases is very irregular and difficult to find. The Range is important as 
being a practical test of the purity of the material used in the manufacture 
of the carbon, an increase of a quarter of one per cent of impurity making 
a very decided reduction in the extent of the Range. The hissing-point 
should be 4 or 5 volts below the normal adjustment of the lamp to insure 
steady burning. 

Resistance. — The resistance is measured on an ordinary Wheatstone 
bridge. Care must be taken that the contact points go slightly into the 
carbon. A /g" x 12" plain carbon should have a resistance of between .16 
and .22 ohms, and £"x 12" between .14 and .18 ohms. T 7 5 " x 12" carbons coated 
with three pounds of copper per thousand, have a resistance between .05 and 
.06 ohms, and \" x 12" with four pounds of copper between .04 and .05 ohms. 

JLitV. — The life of a carbon is most easily tested by consuming it 
entirely in the lamp, observing, of course, the current and average voltage 
during the entire time. A very quick and accurate comparative test of dif- 
ferent cai'bons can be made, however, by burning the carbons to good points, 
then Aveighing them, and let them burn one hour, then weigh them again. 
The amount burned by both upper and lower carbons shows the rate of 
consumption Avhich Aviil accurately indicate the comparative merits of the 
carbons tested as to life. 



ARC LAMPS. 



397 



To calculate the life from a burning test of one hour, both carbons should 
be first weighed, the upper carbon broken off to a 7-inch length, in order to 
make the test at the average point of burning, and with the lower carbon, 
burned to good points, weighed again, and after burning one hour in a 
lamp that has already been warmed up, taken out and weighed. The 
amount of two carbons 12 inches long consumed in a complete life-test is 63 
per cent of the combined weight of both upper and lower carbons. There- 
fore 63 per cent of the weight of the two carbons, divided by the rate per 
hour obtained as above, will give the life approximately. 

JDJiist. — The dust from burning carbons can be collected in the globe, or 
better, in a paper bag suspended below the lamp. In an ordinary plain- 
molded carbon this dust amounts to 4 per cent of the weight of the upper 
carbon. A variation below this amount will indicate good life, but inferior 
light. An excessiA*e amount of dust would show a short life, but usually a 
good quantity and quality of light. Coating a carbon with copper eliminates 
this deposit of dust entirely. 

Inclosed Arc Carbons. 

Carbons for inclosed arcs can be very conveniently tested as to their rel- 
ative values in an open arc lamp as described above. As their diameters 
regulate the admission of air to the inclosing globe, thus greatly affecting 
their life, they should be carefully measured with micrometer calipers. A 
greater variation than .005 // from the required diameter should not be per- 
mitted. The deposit on the inside of the inclosing globe is caused by impu- 
rities, principally in the core. The relative injurious amount of this deposit 
can be measured by carefully taking the globes off the lamps after burning, 
and measuring the amount of light absorbed by them with an ordinary pho- 
tometer, using an incandescent lamp as a source of light, and cutting the 
light down by means of a hole in a screen so that it will pass through the 
part of the globe to be measured. Twice the light so measured through 
the globe, divided by the amount coming through the unobstructed hole, 
will give the per cent of the light transmitted through the globe from the 
arc. That carbon whose globe absorbs the least amount of light is, of 
course, the most desirable. 

The resistance of forced carbons, whether cored or solid, used in inclosed 
arc lamps, is very important. Carbons of high resistance are difficult to 
volatilize, and hence there is trouble in establishing the arc where small 
currents are used, and in case of any interruption in reestablishing it after- 
wards. This is especially true of carbons used in alternating arcs, and of 
cored carbons. The resistance of forced carbons is usually much higher 
than that of molded, ranging from two to four times as much. This will 
undoubtedly be corrected when the manufacturers become more familiar 
with the requirements. The lower the resistance the better the quality of 
the light and the operation of the lamp. 

Sizes of Carltons for Arc Lamps. 



Open Arcs. 


Continuous Current. 


Upper. 


Lower. 


6.8 amperes. 

9.6 

9.6 


12 in. x i 7 B in. 
12" X I •' 
11 " X | " 


7 in. X i 7 B in- 

7 " X i " 

8 " X * " 




Alternating Current. 


15 amperes. 


9^ in. x f in. 


U in. x f in. 



Inclosed Arcs. 


Continuous Current. 


5 amperes. 
3 


12 in. X i in. 5h in. x h in. 
12" X § " 6 " X f " , 



398 



ELECTRIC LIGHTING. 



Some variations are made on the above sizes to change the candle-power, 
or to burn longer. An elliptical carbon g inch X i 7 5 inch x 12 inches is 
sometimes used in a single carbon lamp for all-night service ; and the 12 
and 14 inch x f inch is also used for the same purpose. 



Carbons Recommended for Searchlig-ht Projectors. 

(Hardtmuth or Schmeltzer.) 



Size of Lamp. 


Positive. Cored. 


Negative. Solid. 


12 inch 
18 " 
24 " 
30 " 
36 " 
60 " 


6 in. X f in. 
12 " X U " 
12 " X 1 " 
12 " X n " 
12 " x H " 

12 " x n " 


3^ in. X i 9 B in. 

7 "X|" 
7 "X|" 
7 " X I " 
7 "XI" 
7 » X li " 



Carbons Recommended for tiitomatit and Hand-feed 
focusing* Lamps. 



Continuous Current. 




Amperes. 


Positive. Cored. 


Negative. Solid. 


5 to 10 
10 " 18 
18 " 20 
25 " 30 


6 in. x x 7 5 in - 
6 " X h " 
6 " X | " 
6 " X | " 


6 in. X tb in- 
6 " X £ " 
6 " X | " 
6 " X | " 


Alternating Current. 




5 to 10 
10 " 18 

18 '• 20 
25 " 30 


6 in. X fg in. 
6 " x h " 
6 " X f " 
6 " X | " 


Same as for Positive. 



Candle-power of Arc Lamps. 

The candle-power of an arc lamp is one of the most troublesome things to 
determine in all electrical engineering ; the variations being great the arc 
unsteady, and the implements for use in such determination being so liable 
to error. Again, what is the candle-power of an arc lamp, or rather, what 
is the meaning of the term ? 

When the lamp was first put forward, for some reason, now in great ob- 
scurity, the regular 9.6 ampere lamp was called 2000 candle-power, and it 
has always since been so called, although the word " nominal " has been 
tacked on to the candle-power to indicate that it is a rating, and not an 
actual measurement. 

The candle-power of tbe arc varies with the angle to the horizon on which 
the measurement is made ; in continuous current arcs the maximum can- 
dle-power is at a point about 45 degrees below the horizontal if the upper 
carbon is the positive, and of course above the horizontal if the negative 
carbon is above. 

In alternating current lamps the total light from the arc is somewhat 
more regular in intensity, as both carbon tips are practically the same 
shape. In the arc there are two points of maximum light, one about 60 
degrees above the horizontal, and the other about the same angle below the 



ARC LAMPS. 



399 



line, and the mean horizontal intensity also bears a greater ratio to the 
mean spherical intensity than in the d.c. arc. In the a.c. arc much of the 
light is above the horizontal plane, and it is necessary to arrange a reflector 
above the arc to throw that portion of the light downward ; and this, to- 
gether with a disagreeable hum inherent in the a.c. arc, has much reduced 
the use of that class of lamps except for street-lighting. 

Mean Spherical Candle-power is the mean of the candle-power 
measured all over the surface of a sphere of which the arc is the center, 
usually about one-third of the maximum cand]e-power. In practice the 
spherical candle-power is seldom fully determined, but a fair approximation 
may be had by the following formula : 



Let 



Then 



S = mean spherical candle-power, 
H= horizontal candle-power, 
M= candle-power at the maximum. 
R M 

s —2 +¥• 



In a test of arc lamps in November, 1889, for the New York City Bureau 
of Gas, Captain John Millis found the following results in his trial of the 
Thomson-Houston lamps. 

The same lamp was used, but connected to the different street circuits, all 
measurements were made at 40 degrees below the horizontal, and jVmch 
copper-plated carbons were used. 

Ten readings were taken on each of four sides of the lamp when con- 
nected to each circuit, with the following results : 







Candle-power. 


Watts 


Circuit No. 1. 




2072.7 


482.88 


" " 2. 




1981.0 


485.10 


" 3. 




2048.5 


493.22 


" 4. 




2000.2 


494.40 


" 5. 




2067.0 


495.36 


Means 


amperes 


2033.9 


490.19 


Mean current, 




. . . 10.36 


Mean volts 






. . . 47.32 



The results of tests of candle-power of arc lamps at the Antwerp Exposi- 
tion, shown in the table below, would tend to verify the above trials. 







Maxi- 
mum 
C.P. 




Upper 


Lower 






Am- 
peres. 


Volts. 


Horizon- 
tal C.P. 


Hemi- 
sphere 


Hemi- 
sphere. 


Mean 
C.P. 


Watts, 








Mean C.P. 


Mean C.P. 






4 


37.2 


390 


74 


17 


119 


136 


157 


6 


46.2 


1090 


168 


63 


298 


361 


259 


6.8 


46 


1240 


240 


65 


320 


385 


313 


8 


46 


1550 


334 


70 


385 


454 


350 


10 


45.5 


2070 


421 


102 


640 


750 


491 



Arc Xianip Efficiency. — The efficiency of an arc lamp is the ratio of 
its mean spherical candle-power to the watts consumed between the lamp 
terminals. Some energy is used up in the lamp-controlling mechanism, in 
the carbons themselves, and the remainder is used on the arc. Arc-lamp 
efficiency is sometimes described as the ratio of the watts used in the arc to 
the watts used between the lamp terminals. This is true of the lamp as a 
machine ; but the first statement is the correct one, as it is light that is 
turned out, and not watts consumed in the arc that is the object of the 
lamp, and the two depend so much on quality and adjustment of carbons, 
even with the same consumption of current, as to make the latter method 
erroneous. 



400 ELECTRIC LIGHTING. 



The steadiness of the arc depends somewhat upon the mechanism of the 
lamp, but more largely on the quality of the carbon used. 

The mechanism must be sensitive enough to keep the tips of the carbons 
at practically the same distance apart ; and the quality of carbon must be 
such as to keep the arc steadily in the center, or in the axis of the carbons, 
for if the carbon mixture is not homogeneous, the arc will travel about at 
the outer edge of the carbons, producing bad shadows, Cored carbons, 
having the central axis of the carbon filled with a softer and more volatile 
material, are used for the steadiest light, and in combination with a solid 
negative carbon of a diameter somewhat less than that of the cored positive 
produces most excellent results. 

If W— total watts supplied at terminals, 
w = watts used in the arc, 
1 = current supplied at lamp terminals, 
E = potential between the lamp terminals, 

i = current through carbons or series coil, then the efficiency of the 
lamp as a mechanism is 

w _ ei 
W~ ~BI 

Heat and Temperature Developed l»r the Electric 
Arc. 

The temperature of the crater, or light-emitting surface of the arc, is the 
same as the point of volatilization of carbon, and therefore constant under 
constant atmospheric pressure. This temperature is variously stated by 
different investigators : Dewar gives it as 6000° C; Rosetti, the positive as 
3200° C, and the negative 2500° C. 

The carbon in the crater is in a plastic condition during burning ; and with 
the same adjustment of carbons, as to length of arc, the light per unit of 
power increases with the current. 

Hissing, flaming, and rotating of the arc are some of the defects. Hissing 
is due to a short arc, and was a constant accompaniment of the low poten- 
tial, high current arc so prevalent during the earlier days of arc lighting. 

Flaming and rotating are due to long arcs, and to impure carbons, or 
carbons not properly baked. 

"With good carbons the length of arc, or distance between carbon tips 
recommended by the Thomson-Houston Company, was for 6.8 ampere lamp, 
g 3 5 inch, and for 9.6 or 10 ampere lamps, ^ to ^ inch. 

Heat developed by the electric arc in a given time is as follows : 

Let H= heat in gramme-centigrade degrees. 

i?= difference of potential of arc. 

1 = current in amperes. 

2'= time in seconds. 
Then 

H= .24 EIT. 

Balancing* Resistance for Arc liamps on Constant 
Potential Circuit. 

As the ordinary arc lamp takes but 45 to 50 volts, when used on constant 
potential circuits of more than 50 volts, it is necessary to introduce a cer- 
tain resistance in series, in order, first, to take up part of the voltage, and 
second, to act in a steadying capacity to the arc ; in fact, until the dead 
resistance was introduced in series with the arc lamp on constant potential 
circuits, such lamps were entirely unsuccessful. 

Prof. Elihu Thomson says, " a certain line voltage as a minimum is abso- 
lutely necessary in working arc lamps on constant potential lines, whether 
they be open arcs or inclosed arcs. Thus two 45 volt arcs in series, with 
uncored carbons like the brand known as 'National,' cannot be safely 
worked below 110 volts on the line without resistance in series with them. 
More than 100 volts should, of course, be maintained for safety of the 
service. 



ARC LAMPS. 



401 



" The tests show, also, that with a cored upper carbon, thelimit is lowered 
several volts on the average, and it is known that the voltage of the arcs 
may be safely reduced somewhat when cored positives are used. 

" It is also shown that a 75 to 80 volt arc, run upon a constant potential 
line, is stable at a considerably less line voltage than the open arc. It 
would appear, also, that with either open or inclosed arcs at ordinary cur- 
rent strengths of from 5 to 10 amperes, the steadying resistance in the 
branch is required to cause a drop of about 15 to 20 volts, or waste energy 
at the rate in watts of 15 to 20, multiplied by the amperes of current used in 
the lamp." 

Let E — E.M.F. or difference of potential between the circuit leads 

e — E.M.F. required at arc lamp terminals. 

i = current required by the arc lamp. 
B~ dead resistance to be put in series. 

r = resistance of the arc lamp burning. 
r, = total resistance of dead resistance -f- lamp. 



Then 



(1) 



(2) 



R 



(3) 



As the E.M.F. of most of the circuits on which lamps of this type are used 
is more than 100 volts, it is customary, and in fact economically necessary 
to place two arc lamps in series, and the formula (3) then becomes 



B = r, 



•ir. 



Street lighting- I>y Arc Lamps. 

In New York City 10 ampere arcs are placed at street corners 250 feet 
apart, giving excellent results. On Fifth avenue, New York, two 5 ampere 
lamps on posts placed 125 feet apart, give good results. 

St. Louis, Mo., one arc lamp on every other corner, illumination poor on 
unlighted corner. Favorite distance in United States 200 to 300 feet. 

For good illumination distance apart of arc lamps shoiild not exceed six 
times height of arc from ground. 

For railroad yards 10 ampere arc lamps 30 feet from the ground and about 
200 feet apart are found to give good results. 

The following table shows some arrangements of arc lamps in foreign 
cities : 



Arc Lamps in Foreign Cities. 



City of London Streets 
Glasgow Streets „ . . 
Hastings Streets . . 
Berlin Streets . , . 
Milan Streets .... 
Charing Cross Railroad Station 
Cannon Street Railroad Station 
St. Pancras Railroad Station . 
Central Station, Glasgow . , 
St. Enoch's Station, Glasgow . 
Edinburgh Exhibition, 1886 . 
Edinburgh Exhibition, 1886 . 



Amperes 
per Arc. 



Distance 
apart in Ft. 



115 
160 
300 

137 

to 100 
90 

180 
) to 80 

90 
33 
41 



Height of 
Arc in Ft. 



17.6 
18.0 
18.0 
26.7 
25.0 
18.0 
35.0 
14.0 
19.5 

12.0 
18.0 



402 ELECTRIC LIGHTING. 

About £ watt per square foot is a fair allowance for lighting large halls, 
exhibitions, etc. ; 1 watt for large reading-rooms, libraries, etc. ; 2 watts for 
intense illumination, such as is required at the South Kensington Museum. 



Lig-lir Cut off In Globes. 

Clear glass 10 per cent. 

Light ground glass . . 30 per cent. 

Heavy ground glass 45 to 50 per cent. 

Strong opal 50 to 60 per cent. 



Trimming- Arc Lamps. 

Good trimmer can clean and recarbon about 100 commercial arcs per day 
if the lamps are not too far scattered. 

For street lamps at ordinary distances trimmer should not be required to 
recarbon and clean more than 80 double lamps per day. 



ISTCA]¥DE8CE]¥T LAMP§. 

Temperature of filament should be as high as practicable commensurate 
with an economical life ; it is generally about 2500° F. 

At a temperature of 1800° F. it is said that an increase of 20° in tempera- 
ture will increase the candle-power about 40 times. 

Energ-y required for incandescent lamps is I 2 B or E I; R being the 
hot resistance of the lamp. 

Heat units _£T required is 

H= ~^rw where t = time in minutes. 

Candle-power of a given current varies nearly as the fourth 
power of the difference between the given current and the current required 
to produce visible rays. 

At and near normal candle-power the light varies as the sixth power of 
the current, or 



where _T= current for c. p. 

and i = current for c. p., 



Efficiency of Incandescent 'Lamps. 

By efficiency is understood the ratio of the candle-power to the watts con- 
sumed. It varies from 1 watt to 10 watts per candle, and even more in old 
lamps, but generally in new lamps from 1\ to 4 watts are required. The 
most economical efficiency, i.e., at which the cost of operating the lamp is 
a minimum, depends upon the cost of the energy supplied, and of the lamp 
renewal. When the former is cheap and the lamps poor and expensive, the 
efficiency should be low ; when the reverse holds, the lamps should be run 
at a high efficiency. It has been shown that the total cost of energy and 
lamp renewals is a minimum, where the cost of lamp renewals is about 15 
per cent of the whole. If the renewals cost more than 15 per cent, the 
lamps are being used at too high an efficiency, and vice versa. 

The efficiency of incandescence lamps with direct or alternating currents 
is the same. (Ayrton and Perry.) 



INCANDESCENT LAMPS. 403 



"Watts consumed in incandescent) \2/V^ E 

lamps worked by alternating cur- 
rents 



where 

V/2 — square root of mean square of current measured on electrodyna- 
moineter. 

VJ52 — - square root of mean square of voltage measured on non-inductive 
voltmeter. 
t = the duration of one complete alternation. 
r = resistance of filament in ohms. 
I = coefficient of self-induction of filament. 

Smashing- Point. — It is wasteful to run lamps invariably until they 
break, owing to the decrease in efficiency as the lamp is used. In some 
cases old lamps having very long lives have been found to take as much as 
17 watts per candle. The point at which it is most economical to renew 
the lamp has been termed the" smashing-point," and the following formula 
may be used, on the assumption that the increase in watts per candle-power 
is uniform, or approximately so. 

If 

B — cost of lamps per candle-power, 

C = total cost of a candle-power of light for a given time b, 
D = average cost per hour per candle during the given time b, 
E = cost of energy per 1000 watt-hours, 
a =1 initial power in watts per candle, 

b = hours lamp should be burned, i.e., " smashing-point," 
c = increase of watts per candle for each hour of use ; 
Then 

C=B+(a + cl)E± ro 

n C B , / . b\ E 
2>== -6 = ^+( a + C 2)l000 

D is minimum when b = 4 / 2000 B 
y Eg 

Ib 

b = 1410 y — when c = .001 



and 



b= 815 y E when c = .003 

The Proper Use of Incandescent lamps. 

(From a Circular of the General Electric Company.) 

A lamp to give satisfaction must not only be properly made, but it must 
also be properly used. A lamp of the highest quality may be so misused as 
to give only a small fraction of its rated light capacity. Proper use, produ- 
cing a maximum of light at a minimum expense, requires : 

That the lamps be burned at marked voltage. 

That the voltage be kept constant. 

That lamps be replaced whenever they get dim. 



404 ELECTKIC LIGHTING. 

The last requirement is not considered economical by many users who 
prize lamps that have long life, and insist on using them as long as they 
will burn. Let us see by an example if extremely long life is desirable. 

As the cost of current varies greatly, we will assume an average cost of 
one-half cent per lamp hour. If a rated lG-candle-power lamp, burned 
for 1000 hours, be burned an additional 1000 hours, it takes practically the same 
current during the last period, but gives an average light of only about 8 
candles. The cost of current for the 2000 hours is $10.00. A new lamp costs 
20 to 25 cents; and had three lamps, with a life of about 700 hours each, been 
used during the entire period, the average light would have been fully 
doubled, at an added expense of not more than 50 cents, or 5 % of cost of 
current. In other words, by adding 5 % to operating expense (representing 
the cost of the two renewal lamps) the customer would add 100 % to the 
light given. One new lamp gives a light equal to two old ones at half the 
cost of current. If the old lamps gave light enough, the new lamps would 
halve the number of lamps in use, and produce the same light with half the 
current. 

It is important to note that the above example is based on results obtained 
with the highest grade of lamps. With an inferior quality of lamp the ar- 
gument against extremely long life would be still stronger and the neces- 
sity of frequent renewals of lamps much greater. 

Thus, from any point of view, it is false economy to select lamps with a 
sole regard for long life. Lamps should be renewed when dim, for in no 
other way can light be produced economically. 

The points to be remembered are as follows : 

Do not run pressure above the voltage of the lamps. Increased pressure 
means extra power; and although the old lamps may thus give more light 
for awhile, every new lamp that does not break from the excessive pressure 
will deteriorate very rapidly and give greatly diminished light. 

Do not treat incandescent lamps like lamp chimneys, and use them until 
they break. They should be renewed whenever they get dim. 



JLifV and Candle-power of Lamp*.. 

Since the prime function of an incandescent lamp is to give light, the best 
lamp is that which gives maximum light at minimum cost. This is an ex- 
ceedingly simple axiom, and yet few users of lamps follow it out in prac- 
tice. Lamps are repeatedly selected for long life, irrespective of good, uni- 
form candle-power. Lamps are often continued in use long after their 
candle-power has seriously diminished.' 

An examination of the characteristics of an incandescent lamp will give 
a clear understanding of the principles applying to their selection and use. 
A theoretically perfect lamp would maintain its normal candle-power in- 
definitely, or until the lamp was broken. In practice the deterioration of 
the lamp filament causes a steady loss of candle-power. 

Regarding* Iioss in Candle-no wer. — The drop in candle-power is 
a characteristic of an incandescent lamp always to be borne in mind. The 
relative drop or loss of candle-power, other things being equal, determines 
the comparative value of different lamps. We may have a lamp that loses 
50 % in candle-power inside of 200 hours on a 3.1 watt efficiency basis. This 
type is almost invariably furnished by the inexperienced manufacturer, and 
there are many such lamps in the market. Considered from the standpoint 
of life only, such lamps are excellent, because their filaments deteriorate to 
such a degree that it is practically impossible to supply enough current to 
brighten them up to the breaking point, but no discerning station manager 
would want such dim lamps, even with unlimited life. As in the selection 
of incandescent lamps so in their use — the exclusive consideration of life 
leads to poor results. Loss of candle-power in a lamp sooner or later makes 
it uneconomical to continue in use. 

There is no lamp yel marie which it is economical to burn over 1000 hours, 
and in the great majority of cases the limit is under 600 hours. 



' 



INCANDESCENT LAMPS. 405 

An incandescent lamp is nothing more than a transformer, receiving 
current and transforming it into light. Alter a certain time this trans- 
former may lose 50 % in efficiency, taking practically the same current, but 
giving only about one-half the light. A boiler or an engine suffering such 
loss in efficiency would be promptly repaired or replaced. The renewal of 
incandescent lamps is even more important. The old lamps jeopardize the 
customer's trade with their poor and expensive light. A customer cares 
little how efficiently a station is operated, but is much concerned about the 
quality of light furnished. At the present price of lamps, doubling the 
number of lamp renewals adds little to cost of operation, while it increases 
the lighting efficiency 40 % to 50 %. Some stations attempt to correct the 
dimness of old lamps by raising the voltage, but this is bad practice, for the 
increased pressure damages every new lamp placed in circuit. These prin- 
ciples are carefully observed by many of the large lighting companies, and 
a force of men is employed to weed out and replace all dim lamps. Some 
such means of keeping the average life below 600 hours should be adopted 
by every lighting company that has any regard for the economical produc- 
tion of light, or the satisfaction of their customers. 

A simple method is to fix the average life at 600 hours or less, and then 
determine from the station record how many lamps should be renewed each 
month to keep the average life within this limit. The required number of 
lamps should be renewed each month. 

If, for example, a station decides on an average life not to exceed 600 
hours and the station records show that on the average 60,000 lamp hours of 

current are supplied monthly, then it would be necessary to renew ' or 

bOO 

100 lamps a month. 

The Importance of Crood Regulation. 

Proper Selection and "Use of Transformers. — Poor regulation 
of voltage probably results in more trouble Avith customers than any other 
fault in electric lighting service. 

Some central station managers act on the theory that so long as the life 
of the lamp is satisfactory, an increase of voltage, either temporary or per- 
manent, will increase the average light. The fact is that when lamps are 
burned above their normal rating the average candle-poAver of all the. lamps 
on the circuit is decreased ; and if the station is on a meter basis, it increases 
the amount of the customers' bills. 

Evils of Excessive Voltagre. — Excessive voltage is thus a double 
error — it decreases the total light of the lamps, and increases the power 
consumed. The loss of light displeases the customers and discredits the 
service. If light is sold by meter, the increased power consumption dissat- 
isfies the customers ; if light is sold by contract, the additional power is a 
dead loss to the station. If increased light is needed, 20 candle-power lamps 
should be installed, instead of raising the pressure. Their first cost is the 
same as 16 candle-power lamps ; they take but little more current than 
16 candle-power lamps operated at high voltage, and give greater average 
light. 

Increased pressure also decreases the commercial life of the lamp ; and 
this decrease is at a far more rapid rate than the increase of pressure, as 
shown in the following table. This table shows the decrease in life of 
standard 3.1 watt lamps, due to increase of normal voltage. 

Per Cent of Normal Voltage. Life Factor. 

100 1.000 

101 .818 

102 .681 

103 .662 

104 .452 

105 .374 

106 .310 

From this table it is seen that 3 % increase of voltage halves the life of a 
lamp, while 6 % increase reduces the life by two-thirds. 



406 ELECTRIC LIGHTING. 

Irregular pressure, therefore, necessarily results in the use of lamps in 
which the power consumption per candle is greater than a well regulated 
pressure would allow. The result is reduced capacity of station, and 
reduced station efficiency. 

These remarks apply with special force to alternating current stations, 
since we have here two sources of possible irregularity in voltage — the 
generator and the transformer. Poor regulation is most apt to occur in the 
transformers, and the utmost care should, therefore, be taken in their se- 
lection and use. The efficiency of the average lamp on alternating systems 
is nearly 4 watts per candle. With good regulation obtained by the intelli- 
gent use of modern transformers, the use of lamps of an efficiency of 3.1 
watts per candle becomes practicable. It is thus possible to save 25 % in 
power consumption at the lamps, and increase the capacity of the station 
and transformers by the same amount. 

In the past two years there has been a marked advance in the method of 
making transformer installations. The general adoption of higher voltage 
secondaries gives smaller loss in wires, and permits the use of larger trans- 
former units, thus greatly improving the regulation. On this account 50- 
volt lamps are gradually going out of use. The replacement of a number 
of small transformers by one large unit, and of old, inefficient transformers 
by modern types, has also been of immense advantage to stations. A large 
number of stations, however, still retain these old transformers, and load 
their circuits with large numbers of small units. Such stations necessarily 
surfer from loss of power, bad regulation, and a generally deteriorated 
lighting service. Simply as a return on the investment, it would pay all 
such stations to scrap their old transformers and replace them with large 
and modern units. 

Proper care in the selection of transformers considers the quality and the 
size. Quality is the essential consideration, and should have preference over 
first cost. No make of transformer should be permitted on a station's cir- 
cuit that does not maintain its voltage well within 3 % from full load to no 
load. The simple rule regarding size is to use as large units as possible, 
and thus reduce the number of units as far as the distribution of service 
permits. Every alternating station should aim to so improve regulation as 
to permit the satisfactory use of 3-watt lamps. 

Good regulation is eminently important to preserve the average life and 
light of the lamps, to prevent the increase of power consumed by the lamps, 
and to permit the use of lamps of lower power consumption, so that both 
the efficiency and capacity of the station may be increased. 

Constant voltage at the lamps can be maintained only by constant use of 
reliable portable instruments. No switchboard instrument should be 
relied on, without frequent checking by some reliable standard. Owing to 
the varying drop at different loads, constant voltage at the station is not 
what is wanted. Pressure readings should be taken at customers' lamps at 
numerous points, the readings being made at times of maximum, average 
and minimum load. Not less than five to ten readings should be made at 
each point visited, the volt-meter being left in circuit for four or five min- 
utes, and readings being taken every fifteen seconds. The average of all the 
readings gives the average voltage of the circuits. Lamps should be or- 
dered for this voltage, or if desired, the voltage of the circuits can be re- 
duced or increased to suit the lamps in use. The practical points are to 
determine the average voltage at frequent periods with a portable volt- 
meter at various points of the circuits, and then to arrange the voltage of 
the lamps and circuits so that they agree. 

Candle-Hours — The Reg-ulation of Lamp Value. 

The amount of light given by lamps of the same efficiency is the only 
proper measure of their value. The amount of light given, expressed in 
candle-hours, is the product of the average candle-power for a given period 
by the length of the period in hours. 

Many of the best central station managers consider that a lamp has passed 
its useful life when it has lost 20 % of its initial candle-power. In the case 
of a 10 candle-power lamp, the limit would be 12.8 candle-power. The 
period of time a lamp burns until it loses 20 % of its candle-power may 
therefore be accepted as its useful life. The product of this period in hours 



INCANDESCENT LAMPS. 



407 



by the average candle-power gives the " candle-hours" of light for any 
given lamp. 

The better a lamp maintains its candle-power under equal conditions of 
comparison the greater will be the period of " useful life," and therefore 
the greater will be the " candle-hours." This measure is, therefore, the 
only proper one with which to compare lamps and determine their quality. 

The practical method of comparison is as follows : Lamps of similar 
candle-power and voltage are burned at the same initial efficiency of 3.1 
watts per candle on circuits whose voltage is maintained exactly normal. 
At periods of 50, 75, or 100 hours the lamps are removed from the circuits 
and candle-power readings taken, the lamps being replaced in circuit at the 
end of each reading. Headings are thus continued until the candle-power 
drops to 80 % of normal. The results obtained are then plotted in curves, 
and the areas under these curves give the " candle-hours" and the relative 
value of the different lamps. 



Variation in Candle-power and Efficiency. 

In the following table is shown the variation in candle-power and effi- 
ciency of standard 3.1 watt lamps due to variation of normal voltage. 



Per Cent of Normal 


Per Cent of Normal 


Efficiency in Watts 
per Candle. 


Voltage. 


Candle-power. 


90 


53 


4.68 


91 


57 


4.46 


92 


61 


4.26 


93 


65 


4.1 


94 


69* 


3.92 


95 


74' 


3.76 


96 


79 


3.6 


97 


84 


3.45 


98 


89 


3.34 


99 


94* 


3.22 


100 


100 


3.1 


101 


106 


2.99 


102 


112 


2.9 


103 


118 


2.8 


104 


124* 


2.7 


105 


131* 


2.62 


106 


138* 


2.54 



Example : Lamps of 16 candle-poAver, 105 volts, and 3.1 watts, if burned 
t 98 % of normal voltage, or 103 volts, will give 89 % of 16 candle-nower. or 



at y« % ox normal voltage, or km volts, win give »y %, or ib cancu< 
14J candle-power, and the efficiency will be 3.34 watts per candle. 



-power, or 



JLamj> [Renewals. 

The importance and necessity of proper lamp renewals applies forcibly to 
all stations, regardless of the cost of power, and whether lamp renewals are 
charged for or furnished free. The policy of free-lamp renewals at the 
present low price of lamps is, however, preferable for both station and cus- 
tomer. Free-lamp renewals give a station that full and complete control of 
their lighting service so requisite to perfect results. 

Since, however, a large number of companies charge for renewals, we 
offer sonie suggestions as to the best method of inducing- customers to re- 
new their old iamps, for it is evident that some inducement is necessary. 

Offering new lamps in exchange for dim lamps at a reduction in price is 
one good method. A customer, for example, would save by paying, say 
half price, for the renewal of a dim lamp, instead of waiting and paying 
full price when the lamp burns out. 



408 



ELECTRIC LIGHTING. 



Another method is to offer lamps for renewals at less than cost, say 15 
cents each, and reserve the right to say when lamps shall be renewed. Such 
a plan works well, as no customer can justly complain when the company 
renews lamps at less than cost. 

As profit on the sale of lamps is certainly secondary in importance to the 
sale of current and the improvement in quality of light, either of the above 
plans should commend themselves to all Central Stations not furnishing 
free renewals. 

Whatever method be adopted, the one chief principle of good economical 
lighting service should never be forgotten, viz. : that the average life of 
lamps should never exceed 600 hours. 

Points to l»e Remembered. 

That a constant pressure at the lamps must be maintained. 

That the lamps are not to be used to the point of breakage — they should 
be renewed Avhen they become dim. 

That satisfaction to customers, and the success of electric lighting, are 
dependent upon good, full, and clear light, which old, black, and dim 
lamps cannot give. 

That to furnish a good, full, and clear light 'is as much a part of the 
Lighting Company's business as to supply current to light the lamps. 

That a company should always endeavor to keep the average life of lamps 
within 600 houi's. 

That to renew dim lamps properly on the free renewal system, inspectors 
should examine the circuits regularly when the lamps are burning. If 
lamp renewals are charged to customers, induce them to exchange their 
dim lamps. 

faults in Incandescent lamps. 

Rapid loss of Candle*Power. — Rapid loss of candle-power is 
one defect in incandescent lamps, and we have shown that all lamps suffer 
a gradual loss of candle-power as they are used. A very rapid loss in can- 
dle-power is, however, a real fault, due to inexperienced manufacture, or 
use at excessive voltage. The remedy is to purchase only lamps of standard 
reputation, produced by the experienced manufacturer, and to maintain 
pressure at normal on the lamps. The pressure should be carefully tested 
with accurate portable instruments at the lamp sockets ; and if found high, 
the pressure should be regulated to accord with the voltage of lamps, or 
lamps supplied to accord with the pressure. 

Blackening- of Rull»s. — Another defect in incandescent lamps is the 
blackening of bulbs, although this is more often a supposed defect than a 
real one. A lamp may lose in candle-power and show but little blackening ; 
and on the other hand, a lamp may get quite black and lose little in candle- 
power. Thus a 50-volt lamp which has a more stable filament than the 110- 
volt lamp, often shows considerable blackening with little loss of candle- 
power. 

Blackening in good lamps results from either high pressure or excessive 
life. This is a supposed fault. The best of lamps, if burned too long, will 
always show a certain amount of blackening. The remedies are, of course, 
regulation of pressure and frequent renewals. 

The above are the most important defects to be found in incandescent 
lamps. 

General Illumination. 

The subject of illumination has been divided by Mr. E. L. Elliott, to whom 
we are indebted for many suggestions, into the following sub-divisions : In- 
tensity or Brilliancy, Distribution, Diffusion, and Quality. 

Intensity or Rrilliancy. — The average brilliancy of illumination re- 
quired will depend on the use'to which the light is put. "A dim light that 
would be very satisfactory for a church would be wholly inadequate for a 
library, and equally unsuitable for a ballroom." 

The illumination given by one candle at a distance of one foot is called 
the " candle-foot," and is taken as a unit of intensity. In general, intensity 
of illumination should nowhere be less than one candle-foot, and the demand 



INCANDESCENT LAMPS. 409 

for light at the present time quite frequently raises the brilliancy to double 
this amount. As the intensity of light varies inversely with the square of 
the distance, a 16 candle-power lamp gives a candle-foot of light at a dis- 
tance of four feet. A candle-foot of light is a good intensity for reading 
purposes. 

Assuming the 16 candle-power lamp as the standard, it is generally found 
that two 16 candle-power lamps per 100 square feet of floor space give good 
illumination, three very bright, and four brilliant. These general figures 
will be modified by the height of ceiling, color of walls and ceiling, and 
other local conditions. The lighting effect is reduced, of course, by an 
increased height of ceiling. A room with dark walls requires nearly three 
times as many lights for the same illumination as a room with walls painted 
white. With the amount of intense light available in arc and incandescent 
lighting, there is danger of exceeding " the limits of effective illumination 
and producing a glaring intensity," which should be avoided as carefully as 
too little intensity of illumination. 

Distribution of X>ig-ht. — Distribution considers the arrangement of 
the various sources of light, and the determination of their candle-power. 
The object should be to " secure a uniform brilliancy on a certain plane, or 
within a given space. A room uniformly lighted, even though compara- 
tively dim, gives an effect of much better illumination than where there is 
great brilliancy at some points and comparative darkness at others. The 
darker parts, even though actually light enough, appear dark by contrast, 
while the lighter parts are dazzling. For this reason naked lights of any 
kind are to be avoided, since they must appear as dazzling points, in 
contrast Avith the general illumination." 

The arrangement of the lamps is dependent very largely upon existing 
conditions. In factories and shops, lamps should be placed over each ma- 
chine or bench so as to give the necessary light for each workman. In the 
lighting of halls, public buildings, and large rooms, excellent effects are 
obtained by dividing the ceiling into squares and placing a lamp in the 
center of each square. The size of square depends on the height of ceiling 
and the intensity of illumination desired. Another excellent method con- 
sists in placing the lamps in a border along the wall near the ceiling. 

For the illumination of show windows and display effects, care must be 
taken to illuminate by reflected light. The lamps should be so placed as to 
throw their rays upon the display without casting any direct rays on the 
observer. 

The relative value of high candle-power lamps in case of an equivalent 
number of 16 candle-power lamps is worthy of notice. Large lamps can be 
efficiently used for lighting large areas, but in general, a given area will be 
much less effectively lighted by high candle-power lamps than by an equiva- 
lent number of 16 candle-power lamps. For instance, sixteen 64 candle- 
power lamps distributed over a large area will not give as good general 
illumination as sixty-four 16 candle-power lamps distributed over the same 
area. High candle-power lamps are cbiefly useful when a brilliant light is 
needed at one point, or where space is limited and an increase in illuminat- 
ing effect is desired. 

Diffusion of l^ig-Iat. — "Diffusion refers to the number of rays that 
cross each point. The amount of diffusion is shown by the character of the 
shadow. Daylight on a cloudy day may be considered perfectly diffused ; 
it produces no shadows whatever. The light from the electric arc is least 
diffused, since it emanates from a very small surface ; the shadows cast 
by it have almost perfectly sharp outlines. It is largely due to its high 
state of diffusion that daylight, though vastly more intense than any artifi- 
cial illumination, is the easiest of all lights on the eyes. It is a common 
and serious mistake, in case of weak or overstrained eyes, to reduce the 
intensity of the light, instead of increasing the diffusion.'' 

equality of JLig*ht. — "Aside from difference in intensity, light pro- 
duces many different effects upon the optic nerves and their centers in the 
brain. These different impressions we ascribe to difference in the quality 
of the light. Thus, 'hard light,' 'cold light,' 'mellow light," ambient 
light,' etc., designate various qualities. Quality in light is exactly analogous 
to timber or quality in sound, which is likewise independent of intensity. 
The most obvious differences in quality are plainly those called color. But 
color is by no means the element of quality. The proportion of invisible 
rays and the state of diffusion, are highly important factors, but on account 



410 



ELECTRIC LIGHTING. 



of not being directly visible, tbey bave been generally overlooked, and are 
but imperfectly understood." 

Luminosity of Incandescent X.auips. 

As showing tbe quality of incandescent light, we present here a curve 
showing the relative luminosity of an incandescent lamp at different regions 
of the visible spectrum. 

On this subject Mr. E. L. Nichols states the following : 

" The most important wave lengths, so far as light giving power is con- 
cerned, are those which form the yellow of the spectrum, and the relative 
luminosity falls off rapidly both toward the red and the violet. The longer 
waves have, however, much more influence upon the candle-power than the 
more refrangible rays. 



LUMINOSITY OF 

INCANDESCENT LAMP 

tFERRY.) 




ORANGE YELLOW 



Fig. 6. Regions of Spectrum. 

" Luminosity is the factor which we must take into account in seeking a 
complete expression for the efficiency of any source of illumination, and the 
method to be pursued in the determination of luminosity must depend upon 
the vise to which the light is applied. If we estimate light by its power of 
bringing out the colors of natural objects, the value which Ave place upon 
the blue and violet rays must be very different from that which would be 
ascribed to them if we consider merely their power of illumination as ap- 
plied to black and white. In a picture gallery, for instance, or upon the 
stage, the value of an illuminant increases with the temperature of the 
incandescent material out of all proportion to the candle-power, whereas, 
candle-power affords an excellent measure of the light to be used in a 
reading room." 



Relative Value of Arc and Incandescent Lighting-. 

The relative value of the arc and incandescent systems of lighting is fre- 
quently difficult to determine. Incandescent lamps have the advantage that 
they can be distributed so as to avoid the shadows necessarily cast by one 
single source of light. Arc lamps used indoors with ground or opal globes 
cutting off half the light, have an efficiency not greater than two or three 



INCANDESCENT LAMPS. 411 

times that of an incandescent lamp. Nine 50 watt, 16 candle-power lamps 
consume the same power as one full 450 watt arc lamp. It has been found 
that unless an area is so large as to require 200 or 300 incandescent lights 
distributed over it, arc lamps requiring equal total power will not light the 
area with as uniform brilliancy. 

Xlie Correct Use of Eig-ht. 

Hon to Avoid Harmful Effects on the Eyes. — An objection 
frequently urged against the incandescent lamp is that it is harmful to the 
eyes and ruins the sight. This is true only in so far as the lamp may be im- 
properly used. Any form of light as frequently misused would produce the 
same harmful results. Few people think of attempting to read by an un- 
shaded oil lamp, and yet many will sit in the glare of a clear glass incan- 
descent lamp. Incandescent lamps are more generally complained of, 
because, unlike oil or gas, they can be used in any position. Bookkeepers 
and clerks are often seen with an incandescent lamp at tbe end of a drop 
hanging directly in front of their eyes — an impossible position of the light 
from gas or oil. 

The first hygienic consideration in artificial lighting is to avoid the use of 
a single bright light in a poorly illuminated room. In working under such 
a light the eye is adapted to the surrounding darkness, and yet there is one 
spot in the middle of the eye that is kept constantly fixed on the very bright 
light. The brilliancy of the single light acting on the eye adjusted to dark- 
ness, works harm. There should be a general illumination of the room in 
addition to any necessary local light. If sufficient general illumination is 
provided, the eye is adjusted to the light, and the local light can be safely 
used. The ideal arrangement provides general illumination so strong that 
a pencil placed on the page of a book casts two shadows of nearly equal 
intensity — one coming from the general light and the other from the local 
light. 

Care should also be taken to prevent direct rays from striking the eye. 
The light that reaches the eye by day is always reflected. In reading or 
writing, to avoid shadows, the light should come over the left shoulder. 
Only the reflected rays can then reach the eye. 

Another point to be avoided is the careless, general -use of clear glass, 
unshaded lamps. Frosted bulbs should be used in place of clear glass 
where soft light for reading is required. The intensity of light reflected 
from a small source is increased, and intense light injures the eye. With a 
clear glass globe the whole volume of light proceeds directly from the small 
surface of the lamp filament. With a frosted bulb the light is radiated 
from the whole surface of the bulb, and while the total illuminating effect 
is practically undiminished, the light is softened by diffusion, to the great 
comfort and relief of the eyes. 

Finally, the use of old, dim, and blackened lamps, giving but a small 
fraction of their proper light, is very often a source of trouble in not supply- 
ing a sufficient quantity of light. Users of lamps are not otfen aware of 
the loss in candle-power a lamp undergoes, and so it happens that lamps 
are retained in use long after their efficient light-giving power has vanished. 
Proper attention to lamp renewals on the part of Central Stations is neces- 
sary to correct this evil. 

The correct use of light requires : 

That there should be general illumination in addition to the light near at 
hand. 

That only reflected light should reach the eye. The light should be so 
placed as to throw the direct rays on the book or work, and not in the eye. 

That the light should be placed so that shadows will not fall on the work 
in hand. 

That shades and frosted bulbs should be used to soften the light. 

That lamps be frequently renewed to keep the light up to full candle- 
power. 

life of Incandescent lamps. 

In the early days that lamp which had the longest life was said to be the 
best ; the desideratum, however, as has been seen, is not long life, but 



412 



ELECTJ4IC LIGHTING. 



constancy of candle-power (combined with high efficiency and low cost) dur- 
ing the period of use up to the smashing point. If an initial efficiency too 
high be adopted, the constancy is inferior ; to prove this, Messrs. Siemens 
and Halske have made a number of tests, obtaining the following net 
results : 

1£ initial watts rose to 4.46 watts after burning 55 hours. 
2 initial watts rose to 3.99 watts after 90 hours. 
2j initial watts rose to 3.58 watts after 150 hours. 

The table below contains the mean values of tests of more than 500 lamps 
of 49 different types, and taken from 28 different factories ; The watts per 
candle-power and fall of candle-power are given. 



Table of Average Candl^-Powcr and 'Efficiency of [Lamps 
at Different Periods of their Lives. 









Initial 


Consumption in Watts. 






-4-2 

u 


2.0 to 2.5 


2.5 to 3.0 


3.0 to 3.5 


3.5 to 4.0 


4.0 upwards. 


#2 




ft 




ft 




ft 




a 




ft 


u 




o 




© 




« 




o 




o 


i 


* 


<3 

ft 


* 


<X> 

ft 




3 


e 


<t> 


*£ 


ft 












































3 


Ah 




















a 


ft 


a 


Ph 


rt 


ft 


cS 


ft 


aj 


w 


O 


£ 


O 


£ 


o 


£► 


O ■ 


£ 


O 


!> 





100 


2.4 


100 


2.9 


100 


3.3 


100 


3.8 


100 


4.5 


100 


84 


2.8 


93 


3.0 


95 


3.4 


96 


4.1 


96 


4.7 


200 


70 


3.3 


85 


3.3 


91 


3.5 


91 


4.3 


92 


4.9 


300 


59 


3.7 


81 


3.5 


88 


3.6 


86 


4.5 


87 


5.2 


400 


53 


4.2 


76 


3.8 


84 


3.7 


81 


4.7 


82 


5.4 


500 


48 


4.6 


71 


4.0 


79 


3.9 


77 


5.0 


75 


5.8 


600 


45 


4.8 


67 


4.2 


76 


4.1 


73 


5.3 


72 


6.1 


700 


41 


5.2 


64 


4.4 


72 


4.2 


69 


5.C 


68 


6.4 


800 


39 


5.3 


62 


4.7 


69 


4.4 


66 


5.9 


65 


6.8 


900 


38 


5.5 


59 


5.0 


67 


4.7 


63 


6.1 


62 


6.9 


1000 


37 


5.7 


56 


5.3 


64 


5.0 


60 


6.3 


60 


7.0 


1100 


36 


5.7 


53 


6.0 


62 


5.4 


58 


6.5 


58 


7.1 


1200 


35 


5.8 


50 


6.3 


59 


5.6 


46 


6.7 


56 


,.. 



Distribution of JLig-ht by Incandescent Lamps. 

The best form of lighting interiors is to have single lamps uniformly dis- 
tributed over the ceiling ; unless the room has been especially designed 
with this in view, it is sometimes difficult to accomplish. 

Another method giving most excellent results, but requiring more candle- 
power, is the arrangement of lamps around the sides of the room close to 
the ceiling. If the w r alls and ceiling are of a light color, this method is 
quite satisfactory, and easier to wire. 

If the chandeliers, or more correctly in this case, electroliers, are used, 
it is best to have but one main or large one in the room, balancing the light 
by side brackets. 

All such suspended lights should be above the line of vision as far as con- 
venient. 

The most economical distribution as far as candle-power necessary is the 
first mentioned, where lights are evenly distributed over the ceiling, to 



INCANDESCENT LAMPS, 



413 



obtain the same luminosity by using clusters of lamps more widely distrib- 
uted instead of single ones, will require much more candle-power. 

The 16 candle-power lamp is the universal standard in the United States 
when rating lamps or illumination, and the following table gives the basis 
on which illumination of different classes of buildings is figured. 

Ordinary illumination, 1 lamp, 8 feet from floor for 100 square feet, as in 
sheds, depots, walks, etc. 
In waiting-rooms, ferry-houses, etc., 1 lamp for 75 square feet. 
In stores, offices, etc., 1 lamp for 60 square feet. 

Of course the above must be varied to suit the circumstances, such as dark 
walls or other surroundings requiring more light, as the walls reflect little 
of that furnished ; and in rooms with dead white walls the reflection ap- 
proaches 90 per cent and less lamps would be required than in interiors 
having worse reflecting surfaces. 

A very ingenious and satisfactory method of illuminating high arched 
and vaulted interiors, developed first by Mr. I. R. Prentiss of the Brush 
Company, is to place a number of lamps around the lower edge of the arch 
or dome, with reflectors under them, and so located behind the cornice as 
to be invisible to the eye from the floor. 

The dome or arch will reflect a large part of the light so placed, giving a 
very fine even illumination to the whole interior, without shadows, and very 
restful to the eye. 

Of course the arch must be of good color for reflecting the light, or much 
of it will be wasted. 



Equivalent Rates for Incandescent lig-hting-. 

(Buckley.) 





Without Lamp Renewals. 


Including Renewals. 


Gas per 
1000 Cubic 




^4 




u 
o '— 






Feet. 


teen 
idle-P« 
up per 
ur. 




3 

O 3 


fig, 

Sid: • 


teen 
idle-P( 
up, pe 
nth. 


"3 

© 3 








li 


£3 3,2 


.3 33© 


o o 


$1.00 


$0,005 


$0.42 


$0.10 


$0.0056 


$0.47 


$0.12 


1.20 


.006 


.50 


.12 


.0066 


.55 


.14 


1.40 


.007 


.58 


.14 


.0076 


.63 


.16 


1.50 


.0075 


.63 


.15 


.0081 


.68 


.17 


1.60 


.008 


.67 


.16 


.0086 


.72 


.18 


1.80 


.009 


.75 


.18 


.0096 


.80 


.20 


2.00 


.01 


.S3 


.20 


.0106 


.88 


.22 


2.20 


.011 


.92 


.22 


.0116 


.97 


.24 


2.40 


.012 


1.00 


.24 


.0126 


1.05 


.26 


2.50 


.0125 


1.04 


.25 


.0131 


1.09 


.27 


2.60 


.013 


1.08 


.26 


.0136 


1.13 


.28 


2.80 


.014 


1.17 


.28 


.0146 


1.22 


.30 


3.00 


.015 


1.25 


.30 


.0156 


1.27 


.32 


3.20 


.016 


1.34 


.32 


.0166 


1.30 


.34 


3-40 


.017 


1.42 


.34 


.0176 


1.39 


.36 


3.50 


.0175 


1.46 


.35 


.0181 


1.47 


.37 


3.60 


.018 


1.50 


.36 


.0186 


1.55 


.38 


3.80 


.019 


1.58 


.38 


.0196 


1.63 


.40 


4.00 


.02 


1.67 


.40 


.0206 


1.72 


.42 


4.50 


.0225 


1.88 


.45 


.0231 


1.93 


.47 


5.00 


.025 


2.08 


.50 


.0256 


2.14 


.52 



414 



ELECTRIC LIGHTING. 



Cost of Producing- Electric Light. 

No very general investigation has yet been made on this subject in the 
United States, and few outside the Edison Companies have good facilities 
for determining the cost. Buckley gives the following : 

" The profits on electric lighting depend primarily on the average number 
of hours the lamps burn. Under usual conditions (supplying incandescent 
current through meter including lamp renewals) the cost per lamp per hour 
averages as follows : 



Average Cost of Arc 


and Incandescent lamps per Hour, 




(Buckley.) 








Cost 16 Candle- 


Cost 2000 Can- 


Cost 1200 Can- 


Length Time Burning. 


Power Lamp, 


dle-power Arc, 


dle-power Arc, 




per Hour. 


per Hour. 


per Hour, 


\ Hour each day .... 


$.02 


$0.16 


$0.14 


1 Hour each day .... 


.0112 


•08£ 


.07^ 


2 Hours each day . . . 


.0062 


.05 


.0*4 


3 Hours each day . . . 


.0046 


.04 


.031 


4 Hours each day . . . 


.0037 


•03| 


.03 


5 Hours each day . . . 


.0032 


.03 


M\ 


6 Hours each day . . . 


.0028 


.02| 


.02| 


7 Hours each day . . . 


.0026 


.021 


•021 


8 Hours each day . . . 


.0025 


m\ 


.02 


9 Hours each day . . . 


.0024 


.021 


.015 


10 Hours each day . . . 


.0022 


.02 


.01| 



Notes : — 

An incandescent lamp gives off from \ to ^ s the heat of an equivalent 
gas-jet. 

An arc lamp gives off from ^ to £a as much heat as gas-jets producing an 
equal light. 

A 5-foot (16 c.p.) gas-jet vitiates as much air as four men. 

LI^HTIS^ SCHEDVLE8. 
General Rule for Construction of Schedules. 

Moonlight Schedules. — Start lamps one half hour after sunset 
until fourth night of new moon ; start lamps one hour before moonset. 

Extinguish lamps one hour before sunrise, or one hour after moonrise. 

No light the night before, the night of, and the night after full moon. 

During summer months there will be found nights near that of full moon 
when, under the rule, the time of lighting would be very short. It may not 
be positively necessary to light up during such times. 

If better service be desired, but not full every night and all-night service; 
lamps can be started at sunset and run to 12 or 1 o'clock on full-time sched- 
ule, and after 12 or 1 on the moonlight basis. 

The above rules by Alex. C. Humphreys, M.E., have been modified by 
Fru'nd as follows : Light every night from dusk to 12 o'clock ; after 12 
o'clock follow Humphrey's rule for moonlight schedule, excepting there 
will be no light after 12 o'clock during the three nights immediately pre- 
ceding full moon. 

All-]Vight. Every-I* T ight Schedule . — Start lamps one half hour 
after sunset, and extinguish them one half hour before sunrise every day in 
the year. Full schedule commonlv called 4000 hours for the year. 

All the above rules serve to make schedules for any locality, and such 
schedules must be based on sun time for the locality, and not on standard 
time. 

Permanent average schedules are used in New York City, but for other 
cities they are usually made up fresh every year. 

Following will be found New York City time tables, also another set by 
Humphreys that is a good average for sun time in any locality. 



LIGHTING TABLE. 



415 





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LIGHTING TABLE. 



417 



Summary of lew York City Lighting- Tahle. 



January . 
February 
March „ . 
April . . 
May . . 
June . . 
July . . 
August . 
September 
October . 
November 
December 



Hours for 
the Month. 



h.m. 
413.10 
355.27 
341.29 
21)0.17 
264.39 
238.51 
256.12 
286.26 
316.48 
368.50 
392.59 
424.52 



Average. 



h.m. 

13.19 

12.15 

11.01 

9.40 

8.32 

7.57 

8.16 

9.14 

10.33 

11.54 

13.05 

13.42 



Average 
Day. 



18th 
15th 
16th 
16th 
15th 
12th 
17th 
16th 
15th 
16th 
14th 
10th 



Total hours 



3950 



Shortest 
Longest 

Average 



June 21 

Dec. 21 

Mar. 21 & 

Sept. 21 



h.m. 
7.54 
13.46 



Note. — Lights started SO minutes after sunset. Lights stopped 30 min- 
utes before sunrise. 

For commercial lighting : add 1 hour for part night lights, add 2 hours for 
all night lights to above schedule. 



Tal»le Showing- Hours of Lighting- Throughout a Year of 
S7GO Hours. 



Daily Lighting. 


£ 

i-5 




£ 


! 


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a 

5 


6 

£ 

►3 


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to 
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" 9 " . 

" "10 " . 

" " "11 " . 

" " midnight 
" " " 2 a.m. . 
"4 " . 
From 4 a.m. to sunrise . 
" 5 " " 


125 

15G 
187 
218 
249 
311 
373 
125 
94 
63 


89 

117 

145 

173 

201 

257 

313 

92 

64 

36 


67 
98 

129 

160 

191 

253 

315 

69 

38 

7 


36 
66 
96 
126 
156 
216 
276 
32 
2 


6 

37 
68 
99 
130 
192 
254 
3 






21 
52 
83 

114 
145 

207 
269 
24 


54 
84 
114 
144 
174 
234 
294 
51 
21 


87 
118 
149 
180 
211 
273 
335 
75 
44 
13 


117 
147 

177 
207 
237 
297 
357 
103 
73 
43 


140 

171 
202 
233 
264 
326 
388 
154 
123 
63 


742 
1091 
1456 
1821 
2186 
2916 
3646 
728 
459 


20 
50 
80 
110 
170 
230 


25 

56 
87 
118 
180 
242 


" 6 " " 










254 



















418 



ELECTRIC LIGHTING. 





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J* t-" t>" t-^ t- t~ L- l~ t- 1-" L- t>" I- l- t-" l~ t^ t- L- t- t- t- I- 1-" t-" t>" t-" t- t^ t-" t-" 1-" 




c« O 


tH CM CO rt* ICO CO t- CO O O i-i CM CO "# UO CO tr- CO 05 O *-< Ol CO "*l LO CO 1 -. CO' Ci O t-H 
t-h i-l t-h i-H rH t-h rl i-l t-h t-h Ol CM Ol CM CM 01 Ol CM Ol CM CO CO 



LIGHTING TABLE. 



%L 






3^ 



•0000000000000000000000000000000 

a •*# •* -* -# ■* *# •# •& -^ -^ Kj iq .o 10 o in in o o -+ -v ** -* ■# ■* ■# tjh ■* nj -r ; •# 






IS 



I I 

6«^ 






hO!O^CO'OOO^CDCDCD^C^CO^DOCOO^O^O^OOO^^^OO ( 



r-"ooooooooooooooooooooooooooooooo 
a co co co co co co co co co co co co co cc co co co co m -r -t; n; -r -* -p -t; -r -h ■# tt 1 •# 



el c-i c-i c-i oi ?i oi oi oi oi oi co co co co co co co co co c* co co co co co co co co co 



-LiiOL'jiooiocKiioioiQioiQioiooiooioiaofflooo'-sou'j'o 



o o o o o o o < 

OOffllOlSlOlfli 



N M ■* LO ffl N 00 O O h OI c: -t 1.0 '-2 t- » o O h ' 



co -r io ci t- co coi 



H H H H H ]-l H M rt ci :i :i ci m oi n « ci 



38 



1/ - 

^5 



•OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO 
a 01 01 01 CI 01 CO CO -# -r -# •# IS IO IO l-O lO 30r;HHH ,-h -h r-i CO CO CO CO CO CO 

^ 1-5 rH rH r-5 —H rt" tA H i-H t-H r-i rH 1-H r-H rt i-H Ol' OI 01 c4 01 OI 01 OI 01 01 01 01 OI OI OI 



r- x 

x'a 

y CJD 



s'oooooooooooooooooooooooooo 

30000000HHHHHHHr<HC]ClCl:i:] oi oi oi oi CO 

3 ico id o id id id in 16 id io io id id io ic id id id id id id tiiaodic 



id ud id id io id id 






^ io io io io io io io lo in in io io uo o >o o o 10 lo lo 1.0 io lo uo lo to o q io in 



Hffin^l0«t-(»8!OHNM>fl0 50N00C5O'-iN«-l < 13!0N00OOi 

rt h t-i h h h h rt h h oi oi ci :i :i ci oi ci oi ci nt 



422 



ELECTRIC LIGHTING. 



Hours of Lighting per Annum hy Different Schedules. 

Regular all-night schedule . . . , 4000 hours 

New York City schedule 3950 hours 

Philadelphia schedule 4288 hours 

Providence schedule ...."..,.... 4012 hours 

Philadelphia moonlight schedule ...... 2190 hours 

Frund schedule 3000 hours 



Hours of Burning- Commercial Lights. 

Time of Sunrise and Sunsets. 









o 


o 


ofi 


ofi 


nS 






All 


night 




r< co 

mm 


'yAm 


® 5 


£>CT> 


coco 


43 a 




fs 


CQ 

fj CO 


lights. 




CO ^J 

■\ C 2 


•a « 

P'3 "a 




h.m h.m 


h.m. 


h.m. 


h.m. 


h.m. 


h.m. 


h.m. 






h m 


Jan. 15 


4.55 4.30 


3.30 


4.30 


5.00 


5.30 


6.30 


7.30 


7.25 


8.00 


15 30 


Feb. 15 


5.31 5.00 


3.00 


4.00 


4.30 


5.00 


6.00 


7.00 


6.56 


7.30 


14 30 


Mar. 15 


6.06 5.30 


2.30 


3.30 


4.00 


4.30 


5.30 


6.30 


6.12 


6.45 


13 15 


April 15 


6.41 


6.15 


1.45 


2.45 


3.15 


3.45 


4.45 


5.45 


5.16 


5.45 


11.30 


May 15 


7.13 


6.45 


1.15 


2.15 


2.45 


3.15 


4.15 


5.15 


4.39 


5.15 


10.30 


June 15 


7.37 


7.00 


1.00 


2.00 


2.30 


3.00 


4.00 


5.00 


4.24 


5.00 


10.00 


July 15 


7.32 


7.00 


1.00 


2.00 


2.30 


3.00 


4.00 


5.00 


4.39 


5.15 


10.45 


Aug. 15 


7.00 


6.30 


1.30 


2.30 


3.00 


3.30 


4.30 


5.30 


5.08 


5.45 


11.45 


Sept. 15 


6.09 


5.30 


2.30 


3.30 


4.00 


4.30 


5.30 


6.30 


5.40 


6.15 


12.45 


Oct. 15 


5.19 


4.45 


3.15 


4.15 


4.45 


5.15 


6.15 


7.15 


6.13 


6.45 


14.00 


Nov. 15 


4.39 


4.00 


4.00 


5.00 


5.30 


6.00 


7.00 


8.00 


6.52 


7.15 


15.45 


Dec. 15 


4.31 


4.00 


4.00 


5.00 


5.30 


6.00 


7.00 


8.00 


7.20 


7.45 


15.45 


Aver'ge ) 
for y'r ) 


6.06 j 5.30 


2.30 


3.30 


4.00 


4.30 


5.30 


6.30 


5.54 


6.26 


13.00 



Graphic Lighting Schedule for London, ling-land. 



6 6 7 8 9 10 11 MID.1.AM. 2 3 4 5 6 7 8 9 




Fig. 7. — The shaded area represents the time during which light is 
required. The horizontal lines show the months of the year. The vertical 
lines show the hours of the day and night. The inner dotted lines show the 
time of sunset and sunrise. The outer lines show the time of lighting up 
and extinguishing. Each square is an hour month, i.e., 30.4 hours. 



ELECTRIC STREET RAILWAYS. 

CARS, MOTORS, JLNJ* GRADES. 

(From Pamphlet by S. H. Short, issued by "Walker Company.) 

Grades and sharp curves should of course be avoided as much as possible, 
but when unavoidable, the ascent of a 10 per cent or even a 12 per cent 
grade is possible to a car fitted with a double 15 h. p. or 20 h. p. equipment, 
and pulling no trailer. The grip of the wheels on the rails may be depended 
upon, with the aid of sand, to give from 250 to 300 pounds pull for each ton 
of weight upon them, in even the worst weather. On nearly level roads 
(having nothing steeper than a 2 per cent grade), a single 25 h. p. equipment 
will handle a car, and in a pinch pull a trailer. Ordinarily, however, it is 
not advisable to use a trail car with a single 20 h. p. equipment, as it makes 
a slow start and a slow maximum speed. A single 30 h. p. equipment should 
be able to handle a short car and trailer satisfactorily on roads Avith noth- 
ing greater than 2 per cent grades. While the power of a 30 h. p. motor 
could be depended upon to climb steeper grades, the adhesion of the wheels 
in bad weather cannot be. Single 20 or 30 h. p. equipments will handle 20 
ft. or 22 ft. cars nicely, when no trailer is used, on as high as 4 percent 
grades, and even steeper in good Aveather, the failure being, as previously 
explained, not in the power of the motor, but in the adhesion of the wheels 
to the rails. The 30 h. p. motor has the advantage of the 20 h. p. in giving 
a quicker start and higher speed on grades. Single motor equipments are, 
however, not advisable, on account of the liability of a single pair of drivers 
to slip in bad weather. They Avill prove especially annoying where snow- 
storms are of frequent occurrence, or Avhere the track is liable to become 
icy. All long double-truck cars should have double equipments, as their 
greater Aveight requires greater power to bring them up to speed quickly, 
even on a level. On roads Avith over 4 per cent grades, whether it is pro- 
posed to haul trail cars or not, double equipments should be installed. A 
double 25 or 30 h. p. equipment will handle a trail car on a 6 per cent or 7 
per cent grade, the advantage of the 30 h. p. motors again being the higher 
speed on grades and quicker start. On roads where the traffic is sufficient 
to warrant the use of trailers with short cars, but the grades exceed 7 per 
cent, long cars on double trucks, or radial trucks, Avith double-motor equip- 
ments should be substituted. These will climb nearly as steep grades as 
the smaller cai's, without trailers. Long cars are not advisable except in 
the case just named, and on long runs where the stops are few, as the time 
required for the letting off and taking on of passengers is excessiA'e. 

Finally, on roads Avhere traffic, such, as fairs, base-ball games, etc., has to 
be handled, giving light loads most of the time, but few exceedingly heavy 
ones, the most economical arrangement is that of 30 h. p. double equip- 
ments, hauling tAvo trailers, when the heavy traffic is to be handled. This 
combination can be depended upon for grades not exceeding 3 per cent in 
bad and 4 per cent in good weather. 



CURVES. 

A 30 ft. radius curve on grade adds about as much to the resistance of a 
car as 4 per cent additional grade. It will consequently be frequently 
found impossible to start on such a curve on grade in bad weather without 
sand. Sand boxes should, then, be a part of every car's equipment. Sharp 
curves on grade should always be avoided if possible, as they are the cause 
of great annoyance on wet or icy days. 

423 



424 ELECTRIC STREET RAILWAYS. 



STATIODT. 

A station should never contain less than two dynamos. It is desirable 
also for the steam plant to be composed of two or more units if possible ; 
but on very small roads, say under five cars, this is of course impracticable. 
The general plan of a station should be such that the disabling of one dyna- 
mo or engine could not cause a shut-down on the road. Eor roads of 15 cars 
or less, where the fluctuations of load are exceedingly violent, simple high- 
speed engines are undoubtedly to be preferred. As the road grows larger 
and the load more steady, simple Corliss engines will give a somewhat better 
steam consumption. On a road of 40 cars or more, compound condensing 
engines, of either the Corliss or high-speed type, in units of such size that 
at least one can be kept fairly loaded at all times, will be economical. 
Always condense either simple or compound engines when water for that 
purpose can be had plenty and cheap. Never use compound engines non- 
condensing. Considering the increased expense and complication, together 
with the difficulty in regulating under widely and suddenly varying loads, 
the economy of triple-expansion engines in railway work is doubtful. 

The size of the engine should be always such as to give the maximum 
average efficiency with the variations of load in question. It should be 
noted here that this is not the same size engine which will give the maxi- 
mum efficiency at the average load. 

Where it is possible, belt directly from fly-wheels of engines to generator 
pulleys. Counter shafts give flexibility and make possible the xxse of larger 
steam units, but they consume a very appreciable amount of power, and are 
liable to give trouble otherwise. 

Concerning the amount of power per car in generators and engines, no 
general rule can be laid down, as three variables, viz., grade resistances, 
curve resistances, and traffic, must be considered in this connection. 25 
h. p. (rated at i-J cut off), and 30 amperes per car for roads of 5 to 10 cars, 
and 20 h. p. with 25 amperes per car for larger roads, would probably cover 
the demands. This, however, should be considered only as a rough esti- 
mate. The question of the amount, character, and location of power should 
be settled for each road separately by a thoroughly competent engineer, as 
a small variation from correct principles and design in this respect is liable 
to considerably increase the running expenses. The Avhole design should 
be based on Sir Win. Thomson's principle, namely, that " The interest on 
the investment and the cost of such losses as could have been avoided by 
larger investment should be equal." 

SPECIFICATIONS vs. STANDARD IYPB8. 

The series motor can easily be designed to fill two conditions as to 
speed and power in the same machine, provided always that the condition 
for the lesser power calls also for the greater speed, and that these two 
requirements are not too near alike in speed when the powers called for 
vary widely or vice versa — too near alike in power when the speed varies 
widely. 

Standard motors for street-railway work are now designed to give a 20-ft. 
loaded car a speed of from 20 to 22 miles per hour on a level, and to develop 

NOTE. — Tn the selection of engines for electrical railway work, the best 
practice of to-day is to choose the engines in the same manner as for any 
other commercial manufacturing plant. For large installations, or where 
storage batteries are used for regulating the load, and so retaining fairly 
constant poicer requirements, the size and arrangement of the plant will 
determine whether the engines should be simple, compound, or triple expansion, 
and tohether they should be run condensing or not, if water is available. 

Engines should be designed with all shafts, pins, wearing surface, etc, 
heavy enough for the maximum, loads or over loads, but their cylinders 
should be so proportioned that the averaqe loads be secured at. the most 
economical point of cut-off. This gives strength for heavy load and economy 
for average conditions. 

Countershafts with friction clutches and pulleys are seldom installed 
to-day. Either direct-belted or direct-connected engines and dynamos are 
better, requiring less engine-room area, expense for real estate, building, etc., 
and reduce friction losses and cost of repairs. J- S. G. 



MOTORS AND CAR EQUIPMENT. 425 

their full rated capacity (of 20 h.p., 25 h.p., etc.), at a speed of 10 miles per 
hour, when mounted upon wheels of a specified diameter (generally 33 inch). 

The voltage being kept the same, each speed corresponds to a certain 
horizontal effort or thrust at the circumference of the wheel, this horizontal 
effort increasing as the speed decreases. Therefore, for each different 
tractive resistance, be it due tc the condition of the track, to grade or 
curve, or to whatever cause, has for a given weight of car and load, a given 
speed which cannot be altered without altering at the same time the two 
speeds which the motor was originally designed to give. These speeds are 
most easily altered by changing the diameter of the wheel to a larger or 
smaller size than the standard, according as it is desired to increase or 
decrease the speed, or in S. R motors by changing the ratio of the gearing. 

In asking for designs for special motors, the weight of the maximum train 
and the maximum speed on level, together with the weight of the maximum 
train and the highest speed on the maximum grade, should be given. As 
before stated, within limits, any conditions as to speed on level and on 
grade can be approximated by special design. 



DESIRABLE POINTS IN MOTORS AND CAR 

EaUIPMEIT. 

It is desirable that motors should be electrically sound, i.e., that their 
insulation should be high, mechanically strong, and waterproof. It is of 
great advantage in this connection if the entire frame of the motor can be 
insulated from the car truck and consequently from the ground, thus re- 
lieving the insulation of the armature and fields of half the strain. The 
mechanical difficulties in the way of accomplishing this, however, go a great 
way towards counterbalancing the advantage gained. 

A high average efficiency between 3-quarters and full load should be ob- 
tained if possible, but mechanical points should not be neglected to obtain 
this. 

A motor should run practically sparkless up to § of its rated capacity. A 
low starting current is especially desirable, and for obtaining this nothing 
can equal a multiple series controlling device, Avhich cuts the starting cur- 
rent actually in half. This device also enables cars to run at a slow speed 
with far greater efficiency than any other method. 

Mechanically, the motor should be simple. The fewer the parts, and es- 
pecially the wearing parts, the better, It should be well encased in a cover- 
ing strong enough not only to keep out water, pebbles, bits of wire, etc., 
encountered on the track, but to shove aside or slide over an obstruction 
too high to be cleared. At the same time, the case should be hinged so 
that by the removal of a few bolts access can be had to the whole interior 
of the motor. The brush holders and commutator should be easily accessi- 
ble through the traps in the car floor at all times. As much of the weight 
of the motor as possible should be carried by the truck on springs ; if 
practicable, all of it. This arrangement saves much of the wear and tear 
on the tracks. 

A switch in addition to the controlling stand should always be provided, 
by Avhich the motorman himself can cut off the trolley current, in case of 
accident to the controlling apparatus. 

Roads having long, steep grades should have their cars provided with a 
device for using the motors as a brake in case the wheel brake gives out. 
There are several methods of accomplishing this, but limited space pro- 
hibits any description of them. 

Last, but by no means least, all wearing parts should be capable of being 
easily and cheaply replaced. 

NOTE. — Double brakes or track brakes should be used on roads ivith 
steep grades. Power brakes are seldom used on ordinary cars. With the 
increase in the length and weight of cars they will probably come into more 
general use, and orders have been issued by the Railroad Commission of the 
State of New York that all street cars must be equipped with power brakes. 

J. S. Gc 



426 



ELECTRIC STREET RAILWAYS. 
WEIGHTS Of RAILM. 



Pounds per 


Weight per Mile. 


Weight 


per 1000 7 . 


Yard. 


Long Tons. 


Long 


Tons. 




640 




^986.7 




25 


39 2240 
320 


39.286 


7 2240 
2080 


7.441 


30 


47 2240 


47.143 


8 2240 


8.929 


35 


55 


55 


933.3 
10 ~2240 


10.417 




1920 




2026.6 




40 


62 2240 
1600 


62.857 


11 2240 

880 


11.905 


45 


70 2240 


70.714 


13 2240 


13.393 


48 


960 

74 2240 

„ 1280 


74.428 


635.5 
14 2240 
1973.3 


14.284 


50 


78 2240 
1600 


78.571 


14 2240 
1066.7 


14.881 


52 


81 2240 
960 


81.714 


15 2240 
826.6 


15.477 


55 


86 2240 


86.428 


16 2240 


16.369 


56 


88 
320 


88 


1604.4 
16 ~2240 

586.7 


16.667 


58 


91 2240 
2080 


91.143 


17 ^240 
^1920 


17.262 


58J 


91 2240 
640 


91.928 


17 2240 
920 


17.411 


60 


94 2240 
960 


94.286 


17 2240 
1013.3 


17.857 


62 


97 2240 


97.428 


18 2240 
1680 


18.452 


63 


99 
1760 


99 


18 2240 
2013.3 


18.75 


63£ 


99 2240 

,™ 32( > 


99.785 


18 ~2240~ 
773.3 


18.899 


65 


102 2240 
in „1600 


102.143 


19 2240 
1440 


19.345 


66 


103 

2240 


103.714 


19 2240 
1773.3 


19.643 


66£ 


104 2240 


104.5 


2240~ 
2106 


19.792 


67 


105 

2240 

™ 1920 


105.286 


1Q 

2240 

533.3 


19.940 


68 


106 2-240 


106.857 


20 2240 
2000 


20.238 


70 


110 
111280 

2240 


110 


20 2240 
293.3 


20.833 


71 


111.125 


21 "2240 


21.131 



WEIGHTS OF RAILS. 427 

WXIGHTi OF R AIL§ — Continued. 



Pounds pei- 


"Weight per Mile. 
Long Tons. 


Weight per 1000 '. 


Yard. 


Long 


Tons. 




320 




960 




72 


113 2240 
1920 


113.143 


21 2240 

720.2 


21.429 


75 


117 2240 


117.857 


22 2240 
2053.3 


22.322 


77 


121 
«™320 


121 


99 

"" 2240 
480 


22.917 


78 


122 

2240 
1600 


122.143 


9°. 

Zo 2240 
1813.3 


23.214 


80 


125 2240 
1920 


125.714 


23 2240~ 
906.6 


23.810 


82 


129 2240 
1280 


129.857 


24 ~2240 
666.6 


24.405 


85 


133 2240 
960 


133.571 


25 2240 
1760 


25.298 


90 


141 2249 


141.428 


2G 2240 
186.6 


26.786 


91 


143 


143 


27 2240 
373.3 


27.083 


98 


154 
320 


154 


29 2240 
1706.7 


29.167 


100 


157 2240 


157.143 


29 ~2240~ 


29.762 



For iron or steel weighing 480 lbs. per cubic foot : Cross-section in square 
inches = weight in lbs. per yard -f- 10. 

For iron or steel having \ conductivity of copper : Weight in lbs. per yard 
-f- 11.6333 — number of 0000 B. & S. copper wires with combined equivalent 
carrying capacity. Also, weight in lbs. per yard x 18189.1 = C. M. of equiva- 
lent copper wire. 

it 4 l»l 1 * OF CURVES FOR DIFFERENT DEGREES 
OF CERVATURE. 



tc 




02 




02 




02 




02 










02 






<v 


02 


© 


02 


<D 


«.2 


<D 


-S.H 


<D 


<D.£ 


<v 


■83 


© 


*£ 




Qt3 




r «"73 


bo 


fi'TS 


bo 


©73 


bfi 


®T3 




PH e3 


<S 


&H CS 


<v 


fc S3 


CD 


PR c$ 


© 


pH S3 


A 


« 


A 


« 


w 


« 


A 


« 


A 


S 


1 


5730 


11 


521 


21 


273 


31 


185 


41 


139 


2 


2865 


12 


477 


22 


260 


32 


179 


42 


136 


3 


1910 


13 


441 


23 


249 


33 


174 


43 


133 


4 


1432 


14 


409 


24 


238 


34 


169 


44 


130 


5 


1146 


15 


382 


25 


229 


35 


163 


45 


127 


6 


955 


16 


358 


26 


220 


36 


159 


46 


125 


7 


818 


17 


337 


27 


212 


37 


155 


47 


122 


8 


716 


18 


318 


28 


206 


38 


150 


48 


119 


9 


636 


19 


301 


29 


197 


39 


147 


49 


117 


10 


573 


20 


286 


30 


191 


40 


143 


50 


114 



Note No. 1. — A 1° curve has a radius of 5730 feet; 2° curve, £ this ; 3° 
curve, i this, etc. 



428 



ELECTRIC STREET RAILWAYS. 



GRADEft 


II PER CEIT All» M B ft IE 1HT EEEOT. 




Rise in Feet at Given Distances. 


Per Cent Grade. 










500 Feet. 


1000 Feet. 


5,280 Feet (1 Mile). 




2.5 


5 


26.4 


1 


5 


10 


52.8 


1.5 


7.5 


15 


79.2 


2 


10 


20 


105.6 


2.5 


12.5 


25 


132 


3 


15 


30 


158.4 


3.5 


17.5 


35 


184.8 


4 


20 


40 


211.2 


4.5 


22.5 


45 


237.6 


5 


25 


50 


264 


5.5 


27.5 


55 


290.4 


6 


30 


60 


316.8 


6.5 


32.5 


65 


343.2 


7 


35 


70 


369.6 


7.5 


37.5 


75 


396 


8 


40 


80 


422.4 


8.5 


42.5 


85 


448.8 


9 


45 


90 


475.2 


9.5 


47.5 


95 


501.6 


10 


50 


100 


528 


11 


55 


110 


580.8 


12 


60 


120 


633.6 


13 


65 


130 


686.4 


14 


70 


140 


739.2 


15 


75 


150 


792 



Note No. 1. — For other distances interpolate the table by direct multi- 
plication or division. 

EliEVATIOHr OE OVTER RAIL OH CURVES. 



5c.?, 



5730 

2S65 

1910 

1432 

1146 

955 

818 

716 

636 

573 

521 

477 

409 

358 

318 

286 



Speed in Miles per Hour. 



10 



•JO 



25 



30 



35 



40 



45 



50 



Elevation of Outer Rail in Inches. 



f 

I, 

i| 

2ft 
24 
2| 
3ft 



1 

ft 

*§ 

4 
hi 

2ft 

24 
2| 
3 

O 6 

• 5 T5 

3*3 

4| 



3ft 

m 

4* 

414 

54 

5*1 
6*§ 

7 5 

4 



5 


ffl 


1ft 


If 


1*4 


24 




1*4 


2ft 


2* 


2ft 


4*g 


n 


24 


3ft 


44 


54 


7* 


2A 


3g 


4# 


4ft 


m 


a* 


3ft 


4ft 


5 TB 


«ft 


84 


12ft 


3*4 


5 


^ 


84 


104 




4ft 


5f 


^ 


9ft 


llf 




4*1 


6*4 


S** 


104 






b* 


7* 


y * 


12*g 






S* 


8ft 


102- 








4 


94 


Hrl 








7ft 


9*& 


1Z TB 








8ft 


11+ 










9*4 












io» 












12 













60 



Note No. 1.— When E = elevation in inches of outer rail above the hori- 
zontal plane: 

V: 
R 



Therefore E 



velocity of car in feet per second ; 
radius of curve in feet ; 

V 2 
1.7879 :_— when gauge of track is 4 / -8+ / 

R 



_ 



SPIKES. 



429 





SPIMES. 






Size. 


No. per Keg of 
200 Lbs. 


Lbs. per Spike. 


Spikes per Lb. 


4§ X h 


533 


.3752 


2.66 




5 X/s 


650 


.3077 


3.25 




5 X i 


520 


.3846 


2.6 




5 X T 9 6 


393 


.5089 


1.96 




H x h 


466 


.4292 


2.33 




5| X is 


384 


.5208 


1.92 




6 X T 9 6 


350 


.5714 


1.75 




6 Xf 


260 


.7692 


1.3 





SPIKI!§ PER 1©©©' AHHO PER 9EEEJB SIWGULE 
TRACK, WITH EOUR SPIKES PER TIE. 





Spacing 


of Ties. 


Per 1000'. 


Per Mile. 




1333A 

1466| 

1600 

1733| 

1866§ 

2000 

2133J 


7040 




i « a 


7744 


12 " 


l U (« 


8448 


13 " 


i (< it 


9152 


14 " 


I (( u 


9856 


15 " 


( (( (< 


10560 


16 " 


' « " 


11264 





JOIBfTi PER 


MILE 


OE §061E 


TRACK. 




Per 1000'. 


Per Mile. 




30' rails . . . . 




66| 

133§ 
266§ 
400 

533g 

800 


352 


Angle 
Bolts 






704 


— 4 bole bars . . . 
6 " " . . . 




1408 
2112 


u 


8 " " . . . 




2816 


" 


12 " " . . . 




4224 



TIES PER lOOO' AMR PER MI1E. 



Spacing. 


Per 1000'. 


Per Mile. 


10 ties to 30' rail 

11 " " " ' 

12 " " " " 

13 " " " " 

14 " " " " 

15 " " " " 

16 " " " " 


333£ 

366| 

400 

433J 

466§ 

500 

533§ 


1760 
1936 
2112 
2288 
2464 
2640 
2816 



HOARD EEET, CUBIC EEET, AjVR SdUABX EEET 
OE REAROG SURE ACE PER TIE. 



Size. 


Board Feet. 


Cubic Feet. 


Bearing Surface 


5" X 5" X V 


14.56 


1.213 


2.91 


5" X 6" X V 


17.5 


1.458 


3.5 


5" X 7" X V 


20.41 


1.7 


4.08 


5" X 8" X 7' 


23.33 


1.944 


4.66 


6" X 6" X 7' 


21 


1.75 


3.5 


6" X 7" x r 


24.5 


2.041 


4.08 


6" X 8" X V 


28 


2.333 


4.66 


6" X 9" X V 


31.5 


2.625 


5 25 


6"xl0" X 7' 


35 


2.916 


5.83 


6" X 8" X 8' 


32 


2.666 


5.33 


6" X 9" X W 


36 


3 


6 


6"X10" X 8' 


40 


3.333 


6.66 



430 



ELECTRIC STREET RAILWAYS. 



REPORT OF U. S. DEPARTMEW1 Of AGRICU1- 
ll T BK OUT DIRABILITV OJF RAILROAD TIES. 

White oak 8 years. 

Chestnut 8 

Black locust 10 

Cherry, black walnut, locust 7 

Elm G to 7 

Red and black oaks 4 to 5 

Ash, beech, and maple 4 

Redwood 12 

Cypress and red cedar 10 

Tamarack 7 to 8 

Longleaf pine 6 

Hemlock 4 to 6 

Spruce 5 

Paving prices vary so that it is difficult to state even an approximate cost 
that will not be dangerous to use. Prices are not at all alike for asphalt, 
even in cities in the same localities ; other styles vary according to prox- 
imity of material, cost of labor, and amount of competition. 

Square yards of paving between rails, 4 / 8|" gauge, less 4" for width of 
carriage tread : 

Per 1000' run = 485.89 sq. yards. 
Per mile run = 2565.5 
Square yards paving for 18" outside both rails : 

Per 1GW run = 333§ sq. yards. 
Per mile run =z 1760 " 



Approximate Cost of Paving*. (D 


ivis. 


) 










Cost of 










Tearing up 




Cost of all Material 
and Labor. 


Existing 
Pavement 










and Repla- 










cing as 










Found. 


PAVEMENT. 










-d 




O o 


0) 


<nM 




>n 


aix 


«g 


&M 


• a 




a 1 

>J1 


O c$ 






as 




3 


£H 


£l? 


HH ■-{ 


£w) 




^ 




Qj.3 

W 02 


(a 


W «2 


Granite blocks on gravel foundation 


$ 
2.80 


$ 
2.24 


12000 


$ 
.35 


$ 

1900 


Gravel blocks on concrete foundation . 


3.60 


2.88 


15500 


.45 


2400 


Asphalt on concrete foundation . . . 


3.80 


3.04 


16000 






Vitrified brick on broken stone .... 


2.15 


1.72 


9000 


45 


9400 


Wood without concrete 


1.50 


1.20 


8000 






Cobble without concrete 


2.00 


1.60 


8500 


.30 


1600 


Macadam 


1.00 


.80 


4500 


.50 


2700 



K8TISIATE OF TRACK IAYO« FORCE. 

One engineer, 1 rodman, 1 foreman of diggers, 1 foreman of track-layers, 
4 spikers, 20 laborers. 2 general helpers. Such a gang can lay from 400 to 
900 feet of single track per day. 

In case it is desired to proceed more rapidly, the above number of men 



PAVING. 



431 



should be increased proportionately, omitting the engineer and rodman, as 
these two will be able to handle any ordinary number of gangs, no matter 
how widely scattered, if a horse and buggy is placed at their disposal. 

Tool* for Track Gang 1 as Above, 

One portable tool-box padlocked, 1 small flat car, 1 portable forge, 4 cold 
chisels, 2 ball pein hammers, 6 lbs. ; 1 sledge, 12 lbs. ; 2 axes, 2 adzes, 1 cross- 
cut saw, 1 large double-handled saw, 6 track wrenches, 2 monkey wrenches, 
1 complete ratchet track drill with bits, 1 track " Jimmy " for bending rails, 

1 reel line cord, braided : 30 picks, 15 extra pick-handles, 25 long -handled, 
roundnose shovels, 6 short handled, square-nose shovels, 10 tampers, 5 
wheelbarrows, 2 track gauges, 1 level, 1 straight-edge, 4 pair rail tongs, 6 
spiking hammers, 3 crow-bars, one end sharp, the other end chisel-pointed, 

2 spike claw-bars, 1 engineer's transit, 1 leveling-rod, 10 surveyor's marking- 
pins, 1 steel tape, 10 red lanterns, 1 box lump chalk, 1 squirt oil-can, 1 quart 
black oil , 5 gals, kerosene, 1 flag-rod, 1 paper of tacks, 1 broad blade hatchet. 

MAJX.WA.Y TU»]¥©1JTS. 

By W. E. Harrington, B. S. 

For example, assume a railway to operate 4 cars, the distance between 
terminals four miles, the time of round trips 60 minutes, and the headway 
15 minutes, with a lay over at each end of five minutes. Take a piece of 
cross-section paper, and make the 
vertical lines represent distance, v A| B 

and the horizontal lines represent 
time. 

The time necessary to run from 
terminus to terminus is half of 60 
minutes, less \ of ten minutes (the 
layover time), or 25 minutes. Let 
each division on the ordinate axis 
represent the distance traversed by 
a car in one minute, which in the 
above case is 844.8 feet per minute,as- 
suming that the car is to run at the 
average speed of 9.6 miles per hour. 
Let each division on the axis of ab- 
scissas represent five minutes. The 
first car will travel from terminus to 
terminus as represented by the diag- 
onal line OA. This line shows the 
car's position at any instant of 
.time, assuming, of course, that the 
car is running at a uniform rate of 
speed. The car upon its arrival at 
the other terminus will have a lay- 
over of five minutes as repre- 
sented by the horizontal space AB. 
Upon the expiration of the time of lay-over the car starts upon its return 
run. This determines the locus of the several turnouts, as the car has to 
pass each of the remaining cars. The line of the return run is represented 
by the line BC. Upon the arrival of the car at the original terminus and a 
lay-over of five minutes, the cycle of trips will be repeated. During the 
time the first car is running its round trip the other cars are leaving at in- 
tervals of 15 minutes, as represented by the lines DE, FG, and HI. Where 
these three lines intersect the line BC turnouts must be located, as the cars 
meet and pass at these points. The distance apart of the turnouts, as well as 
their distance from the starting terminus O, may be readily determined by 
projecting the intersections on the axis of ordinates OY. 

1. The number of turnouts for a given number of cars is one less than the 
number of cars running. 




P F 

j* 60 A 

Fig. 1. Location of Street Railway 
Turnouts. 



432 



ELECTRIC STREET RAILWAYS, 



2. The time consumed running between turnouts must be the same 
between all the turnouts. For instance, if it is found necessary to irregu- 
larly locate turnouts for any reason, then the time consumed by a car run- 
ning between these two turnouts farthest apart determines the time the 
cars must run between the remaining turnouts, even though two or more of 
the turnouts be only a slight fraction of the distance apart of the two 
greater ones. 

3. The time consumed running between two consecutive turnouts is one- 
half the running time between cars. 

For determining the distance apart of turnouts without the aid of graph- 
ical methods : 

Rule. — To the length of the railway from terminus to terminus add the 
distance a car would travel running at the same rate of speed as running on 
the main line, for the time of lay-over at one terminus. Divide the above 
result by the number of cars desired to be run, the result is the distance 
between turnouts. Multiply this latter result by two less than the number 
of cars, and deduct the result obtained from the length of the line from ter- 
minus to terminus, and divide by two. The result is the distance from 
either terminus and the first adjacent turnout. 

To operate more or less cars on a railway than it is designed for is a ques- 
tion most frequently met in railway practice. 

Rule 1 tells iis that we must have one turnout less than the number of 
cars running. In Fig. 1 we have four cars and three turnouts. If we pro- 
pose running three cars we would use two turnouts, by omitting the middle 
turnout. The result is at once apparent ; for according to Rule 2, the time 
to run between turnouts is determined by the time consumed in running 
between those two turnouts farthest apart. Since the distance is doubled, 
the time consumed is doubled. "Wherewith four cars, with fifteen minutes 
between cars, and sixty minutes for the round trip, with three cars the time 
between cars as by Rule 2 is thirty minutes, and the time of round trip is 
ninety minutes, making at once a very pronounced loss. 

The better plan, and the one usually pursued by railway managers, is to 
run the lesser number of cars on the same trip time as the railway was 
designed for. In our example above, the three cars would be run as if the 
four cars were running, with the exception that the space which the car 
should be running in will be omitted, leaving an interval between two of 
the cars of thirty minutes, giving only the loss occasioned by the omission 
of one car. 

Another method to pursue, especially so where additional cars will be 
run at times, such as holidays, exem*sions, and other times of travel requir- 
ing more than the regular number of cars to accommodate the travel, is to 
provide and locate more turnouts. The expense of doubling the number of 
turnouts, while they would be a great convenience, would not be warranted 
without the railway were doing a large and growing business, with a fluctu- 
ating number of cars in service. Two cases should be considered. 

First — If a certain fixed number of cars are to be operated for the greater 
portion of time and the extra cars for odd and infrequent intervals, locate 
the turnouts to suit the regular business. 

Second — In the case of a railway running an irregular number of cars — 
for instance, a railway running a heavy business at certain times of the day 
— as the lesser number of cars are subordinate to the greater number, 
locate the turnouts to run the greater number of cars the most efficiently. 

In conclusion, we might state that the grades, the running through 
crowded business streets, stoppages occasioned by grade railroad crossings, 
and varying business, all enter in and must be considered while designing. 

Block Signal for $ing-le-Track Roads or for Bridg-es, etc. 

M. S. Wightman has designed a system which is operated automatically 
by the passage of the trolley wheel along the wire, as follows : 

Suppose a car passing south from the north siding, its trolley makes con- 
tact at " make hanger a'," current passes through magnet A / , white lamps 
W', plunger contacts RS — AVSR — red lamps R / to ground. Plunger is then 
raised connecting contacts TM. Current then flows from trolley through 
contacts TM, magnet A 7 , white lamps W', contacts WSM — L, — line, con- 



RAILWAY TURNOUTS. 



433 



tacts in box at south switch, L — WSM, contacts WSB — RS, through the 
red lights to ground. This condition remains until the car passes " break 
hanger" contact a 2 ; the trolley while striking the " break hanger a 2 " mo- 
mentarily excites magnet B, raising the plunger and breaking the signal 



WIGHTMAN BLOCK SIGNAL 




TROLLEY WIRE 




Fig. 2. 

circuit at WSM — L, this in turn de-energizes magnet A 7 , its plunger drops 
to its normal position, breaking the circuit at TM, and the signal is " off." 
The same action in a reverse direction takes place when a car passes out of 
the south siding going north. 

Another method, a manual one, is in use by the Lehigh Valley Traction 
Co. on all the street railways in and about Allentown and Bethlehem, Penn. 
One advantage claimed for this system over an automatic method is, that 
the conductor is responsible for maintaining his own right of way. 

The system is operated as follows : A conductor before entering a section 
between switches pushes a switch-rod, which sets a signal at the turnout 

SIGNAL SETTING BOX 




Fig. 3. 



ahead, a magnet operating a red semaphore and incandescent lamps be- 
hind a red glass disk. This makes the signal visible both night and day. 
This semaphore stays set until he reaches the switch ahead ; then the con- 
ductor opens the circuit which sets the track behind him to safety. If on 
reaching the switch he finds the semaphore is set to danger, he has to wai$ 



434 



ELECTRIC STREET RAILWAYS. 



on switch until car passes. Conductors only set semaphores ahead of them 
and release those behind ; the car is controlled by semaphores operated by 




ROLLEY WIRE 





I 


f 1 






c 




l> ' 








Fig. 4. 

the conductors of cars passing it at the switches, and the signal systems for 
cars operating in opposite direction are entirely independent. In each 



SIGNAL RELEASING BOX 




TO GROUND / e ^^ / 



Fig. 5. 



signal box there is also a pilot lamp which is extinguished when the section 
of track is opened, and illuminated when the section is closed ; this gives 



RAILWAY TURNOUTS. 



435 



the conductor knowledge that his signals have operated properly at the 
distant switch. As the first signal set gives the right of way, there is no 
meeting between switches. The detailed description is given below. 

There are three separate operating parts, — a signal setting-box, a signal 
releasing-box, and the semaphore box. 

The signal setting-box is shown with details in Fig. 3. The magnets are 
1| in. x 1^ in. winding-space with fiber heads, and ^ in. core ; the end of the 
iron cores exposed to the armature are tipped with platinum or silver, and 
the armature B is also faced as these surfaces come together and complete 




the circuit and are held in contact by this current also passing through the 
magnets. The armature B normally rests out of the influence of its magnet. 
A rod entering from the bottom of this box shoves the armature up into con- 
tact with the ends of the magnet, and is held in this position until the circuit 
is broken. 

The current from the trolley enters first through a lamp, then through 
the magnet-winding to the frame. When the armature is up the current 
passes down the arm holding the armature, and then through the signal line 
to the distant semaphore box. 

The semaphore box contains a pair of solenoid magnets, which set the 
semaphore disk and light the lamps. These lamps are arranged behind a 
red glass disk inserted in the semaphore box. The disk is set by means of a 
solenoid operating a bell crank and link, which turns the semaphore rod 
and displays the red disk. The dimensions and methods of general con- 
struction employed are shown in Fig. 6. The circuit first passes through 
three lamps, then through the solenoid, and out to the signal releasing-box. 
The construction of this box is shown in Fig. 5, and consists of a switch and 
a lamp in circuit with this switch. It is operated by pushing up the rod, 
and when the rod is released the blade falls back into position, but it will 
not close the circuit now ; for on opening the circuit, the magnet in the cir- 
cuit-making box dropped its armature, and opened the current at the dis- 
tant switch, which can now only be closed by the conductor on the car 
following. The diagram of connections is given in Fig. 4. Covered No. 10 
iron wire can be used. Robert Doumblaser developed all the details. 



436 



ELECTRIC STREET RAILWAYS. 



1IST OF MATERIAL REailRED FOR OUSE MIJLE 
OF OVERHEAD JLIJtfE EOR EIEC1RIC 

STREET RAIIWAY. 











1 Mile Overhead. 


Curve Overhead 
* Material. 


Anchor- 


Material for 

Railway 
Construction. 


Cross 
Suspen- 
sion. 


Bracket 

Suspen- 
sion. 


Main 
Line. 


Branch 
Line. 


o 

o 
a 

H 


age. 




Sj 
o 

ft 


H 
3a 


H 

03 

S3 

o 

ft 


H 

03 

"si 

m 


03 

S3 

O 

ft 


H 
be 

.5 
55 


H 

S3 
o 
ft 


H 

03 

02 


© 

S3 

O 

ft 




No. OB. & S. 
H. D. Trolley 


Ft. 
Lb. 


5280 
1685 


10560 
3369 


52S0 
1685 


10560 
3369 










250 
80 




ft 
O 


No. B. & S. 
S.D. F'd'r T'ps 


Ft. 
Lb. 


400 
154 


500 
192 


90 
35 


180 
69 
















3 

H 


7 strand 
No. 12 span 


Ft. 
Lb. 


3600 
756 


3600 
756 






800 
168 


800 
168 


800 
168 


800 
168 


200 
42 


400 

84 


600 
122 




7 strand 
No. 15 guy 


Ft. 
Lb. 


3000 
300 


4500 
450 


1500 
150 


2000 
200 


100 
10 


100 
10 


100 
10 


100 
10 








Plain ears .... 
Strain ears .... 
Splicing ears . . . 
Feeder ears .... 


45 
10 


90 

2 
20 


45 

1 
10 


90 

2 
20 


5 

2 


10 

4 


5 

1 


15 

2 


4 




Insulating caps . . 
Insulating cones . . 


45 
45 


90 
90 


45 
45 


90 
90 


7 


4 
4 


6 
6 


17 
17 


4 

4 






ft"o 

w 


Straight line . . 
Single curve . . 
Double curve . 
Bracket . . . 


45 


90 


45 


90 


3 
4 


3 

11 


3 
3 


5 
12 


4 






Stra 
Tur 
Sect 
Froj 
Fro 
Har 
Eye 
Cas 
Gas 
Cros 


in insulators . . 
ibuckles . . . 
ion insulators 


90 
90 

2 

45 
90 

45 


90 

90 

4 

45 
90 

45 


2 

45 
45 

48 


4 

90 
90 

48 


4 
4 

2 


4 
4 

2 


2 
2 

1 


2 
2 

2 
1 

2 


2 

2 


1 

2 


2 
2 


g crossings . . . 
dwood pins . . 
bolts 


2 


,-iron brackets . 
pipe arms . . . 
s arms (l^'-lS) . 




Cros 

*2L 

r ™ 
Lag 

et 

Lag 

ar 

Lag 


s-arm braces 
/ X8 // ) ..... 


90 

45 
144 


90 

45 
144 


45 

45 


90 
90 
















;s for brackets 
'X4") 

screws for brack- 
s (i"x7") . . . 

screws for cross 
ms (i"x3") . . 
screws for braces 




Poles, 125-ft. apart . 


90 


90 


45 


45 


2 


2 


2 


2 




2 


2 


Channel pins . . . 
Bonds 


800 
400 


1600 
800 


800 
400 


1600 
800 

















Lightning arresters . 


3 


3 


3 


3 














Section switch boxes 


2 


2 


2 


2 

















PLATE BOX POLES. 



437 



Plate Box JP©U»s. 

BY BUFFALO BRIDGE AND IRON WORKS 



OAST IRON 

CROSS ARMS WITH 

STEEL SCREW 




fe£S .'|i', 



'( i 



A- 



■' £ST 



'- ^ 


- 


? 


£ 


V? 




< 

O id 


- 


? 


.X 


,\ 


,-s 


c 


1 


1 


1 


1 


1 



m 



Pig. 7. 



£8 



ELECTRIC STREET RAILWAYS. 



Tl'BrLAR JLROX OR STEEL POLES. 

By Morris, Tasker, & Co. (Inc.). 



Size. 








Wrought Iron or 
Steel. 


Length. 


Weight. 


No. 1, light . 
No. 1, heavy 
No. 2, light . 
No. 2, heavy 
No. 3, light . 
No. 3, heavy 
No. 4, light . 
No. 4, heavy 








5 in., 4 in., 3 in. 

5 in., 4 in., 3 in. 

6 in., 5 in., 4 in. 

6 in., 5 in., 4 in. 

7 in., 6 in., 5 in. 

7 in., 6 in., 5 in. 

8 in., 7 in., 6 in. 
8 in., 7 in., 6 in. 


27 ft. 

27 ft 

28 ft. 
28 ft. 
30 ft. 
30 ft. 
30 ft. 
30 ft. 


350 lbs. 

500 lbs. 

475 lbs. 

700 lbs. 

600 lbs. 
1000 lbs. 

825 lbs. 
1300 lbs. 



POLES. 

Dimensions and Weight* Wroug-ht-Iron and Steel Poles. 



Length. 


Diameter. 


Weights. 


27 ft. 

28 ft. 
30 ft. 
30 ft. 
28 ft. 
30 ft. 


5 in., 4 in., 3 in. 

6 in., 5 in., 4 in. 

6 in., 5 in., 4 in. 

7 in., 6 in., 5 in. 

8 in., 7 in., 6 in. 
8 in., 7 in., 6 in. 


350 lbs. to 515 lbs. 
475 lbs. to 725 lbs. 
510 lbs. to 775 lbs. 
600 lbs. to 1000 lbs. 
775 lbs. to 1260 lbs. 
825 lbs. to 1350 lbs. 



Cubic Contents of Wooden Poles, in Eeet. 



Length. 


Diameter. 


Section. 


Cubic Feet. 


27 ft. 


6 in. X 8 in. 


Circular 


7.36 


27 ft. 


7 in. x 9 in. 


Circular 


9.56 


27 ft. 


7 in. X 9 in. 


Octagonal 


10.1 


28 ft. 


7 in. x 9 in. 


Circular 


9.92 


28 ft. 


7 in. X 9 in. 


Octagonal 


10.46 


28 ft. 


8 in. x 10 in. 


Circular 


12.52 


28 ft. 


8 in. x 10 in. 


Octagonal 


13.2 


30 ft. 


7 in. x 9 in. 


Circular 


10.63 


30 ft. 


7 in. x 9 in. 


Octagonal 


11.21 


30 ft. 


8 in. X 10 in. 


Circular 


13.41 


30 ft. 


8 in. X 10 in. 


Octagonal 


14.15 


30 ft. 


9 in. X 12 in. 


Octagonal 


19.06 



Rake of Poles. 

Wooden poles should be given a rake of 9 to 18 inches away from the 
street. Iron or steel poles set in concrete need be given but 6 to 9 inches 
rake. Corner poles, and those supporting curves, should be given additional 
rake or be securely guyed. 



AVERAGE WEIGHTS OF WOOD. 



439 



AVERAGE WEIGHTS OF VARIOUS WOODS, IS 
POUHTRS. 



Kind. 



Condition. 



Weight per 
Cubic Foot. 



Live oak 

White oak .... 

Red oak 

Chestnut 

Southern yellow pine 
Northern yellow pine 
Long-leaf yellow pine 
Norway pine . . . 

Spruce 

Hemlock 



Perfectly dry 
Perfectly dry 
Perfectly dry 
Perfectly dry 
Perfectly dry 
Perfectly dry 
Unseasoned 
Perfectly dry 
Perfectly dry 
Perfectly dry 



The weight of green woods may be from one-fifth to one-half greater than 
the weight when perfectly dry. 



DIP 



WIRE. 



The following tables 



II¥ SPAS 

(Merrill.) 
ive the dip of the span wire in inches under the 



combined weight of span wire and trolley wire, for various spans and strains. 
Length of trolley wire between supports, 125 feet. Weight of trolley 
wire, 319 lbs. per 1000 feet. Weight of span wire, 210 lbs. per 1000 feet. 

Single Trolley Wire. 



Spans in 




Strain on Poles, in Pounds. 


















Feet. 


















500 


800 


1000 


1500 


2000 


2500 


3000 


30 


7.8 


4.9 


3.9 


2.6 


1.9 






40 


10.6 


6.5 


5.3 


3.5 


2.7 






50 


13.6 


8.5 


6.8 


4.5 


3.4 


2.7 




60 


16.7 


10.4 


8.3 


5.6 


4.2 


3.3 


2.8 


70 


19.9 


12.4 


9.9 


6.6 


4.9 


4 


3.3 


80 


23.2 


14.5 


11.6 


7.7 


5.6 


4.6 


3.9 


90 


26.7 


16.7 


13.4 


8.9 


6.6 


5.3 


4.5 


100 


30.3 


18.9 


15.2 


10.1 


7.6 


6.1 


5.1 


110 


34 


21.3 


17 


11.3 


8.5 


6.8 


5.7 


120 


37.9 


23.7 


18.9 


12.6 


9.5 


7.6 


6.3 





Two Trolley Wires, 1© Feet 


Apart. 






Span in 
Feet. 


Strain on Poles, in Pounds. 




















500 


800 


1000 


1500 


2000 


2500 


3000 


3500 


40 


15.4 


9.6 


7.7 


5.1 


3.9 


3.1 






50 


20.8 


13. 


10.4 


6.9 


5.2 


4.2 






60 


26.3 


16.4 


13.1 


8.8 


6.6 


5.3 


4.4 




70 


31.9 


19.9 


15.9 


10.6 


8. 


6.4 


5.3 




80 


37.6 


23.5 


18.8 


12.5 


9.4 


7.5 


6.3 


5.4 


90 


43.5 


27.2 


21.8 


14.5 


10.9 


8.7 


7.3 


6.2 


100 


49.5 


30.9 


24.8 


16.5 


12.4 


9.9 


8.3 


7.1 


110 


55.6 


34.7 


27.8 


18.5 


13.9 


11.1 


9.3 


7.9 


120 


61.9 


38.7 


30.9 


20.6 


15.5 


12.4 


10.3 


8.7 



Note. — See also chapter on Conductors. 
For table of stranded wire for spans and guys see page 158, Properties 
of Conductors. 



440 



ELECTRIC STREET RAILWAYS. 



Span wires should be stranded galvanized iron or steel, sizes J inch 
diameter f s , \, or § inch according to the weight of trolley wire, etc., to be 
supported. Where wooden poles are used it is not necessary to provide 
other insulation for the span wire, and the wire can be secured to the loop 




-TO SEWER 

Fig. 8. Section of Track and Overhead Construction in Broad Streets, 
showing Double Overhead Wires and Underground Feeder Conduits. 




Fig. 9. Section of Track and Overhead Construction in Narrow Streets, 
showing Overhead Pipe Brace. 

Trolley Suspension for Havana Streets, as developed by 
F. s. Pearson. 



SIDE BRACKETS. 



441 



of an eye-bolt that is long enough to pass through the pole at a point from 
twelve to eighteen inches below the top, and. that has a long thread to allow 
taking up slack. On many roads in the country the span wire is simply 
wrapped around the pole top, using a number of feet more wire, making it 
difficult to take up slack, and presenting a slovenly appearance. Where 
metal poles are used it is necessary to insulate the span wire from the pole 
This has been done in some cases by inserting a long wooden plug in the 
top of tubular poles, capping it with iron, the wooden plug then being pro- 
vided with the regular eye-bolt. The most modern way is to provide a good 
anchor bolt or clasp on the pole, then insert between the span wire and this 
bolt one of the numerous forms of line or circuit-breaking insulators devised 
for the purpose. If the anchor bolt is not made for taking up slack, the insu- 
lating device can be so designed as to be used as a turnbuckle. Of course 
insulation must be provided for both ends of the span wire. 

Span wire must be pulled very taut when erected so that the sag under 
load will be a minimum. Height above rail surface should be at least 18 
feet after the trolley-Avires are in place. This height is regulated by statute 
in some States, and runs all the way from 18 to 21 feet. 

Figures 8, 9, and 10 illustrate one of the most modern installations, that 
at Havana, Cuba, as designed by Mr. F. S. Pearson for double trolley. 



SOLID 
BRONZE 
BOLT) ,. 



^T7 




Fig. 10. Views of Trolley Spans with Plus and Minus Feeder connections 
and Plan of Double Track Y, showing Location of Insulators. 

**I1>E BRACKETS. 

Along country roads and in such places as the track is along the side of 
the roadway or street, it is customary to use single poles with side brackets 
to support the trolley wire. 

Where side brackets are used it is not safe to place the pole less than four 
feet away from the nearest rail, and to give flexibility to the stranded sup- 
porting wire, now always provided for the trolley wire, the bracket should 
be long enough to reach the distant rail, thus giving a little more than two 
feet of cable for flexibility. A common length of bracket is 9 feet. 

Figures 11 and 13 show the simple form of side bracket in most general 
use, and Figs. 12 and 14 show variations of the same. It is obvious that this 
method of support may be made as elaborate and ornamental as may be 
desired. 

On double-track roads center-pole construction is sometimes used, in 
which poles are placed along the center line between the two tracks, and 
brackets are erected on each side of the poles overhanging the tracks. 
Where wooden poles are used a good form of construction is to bore the pole 
at the proper height and run through it the tube for the arms, this long 
tube being properly stayed on both sides of the pole by irons from the pole- 
top to the bracket ends, or by braces against the pole. The trolley support- 
ing wire can extend from end to end of the brackets through the pole, or 



442 



ELECTRIC STREET RAILWAYS. 



can be cut at the pole, and eye-bolts be used, as in tbe side-bracket construc- 
tion shown by Fig. 11. 




Fig. 11. Single Suspension. 
For Wood Poles. 



Figures 15 and 16 illustrate simple forms of center-pole brackets. 




Fig. 12. Single Suspension. 
For Wood Poles. 

Center-pole construction is quite of ten used on boulevards in cities, where 
the brackets and poles can be made quite ornamental. 




Fig. 13. Single Suspension. 
For Iron Poles. 



TROLLEY WIRE SUSPENSION. 



443 




Fig. 14. Single Suspension. 
For Iron Poles. 




Fig. 15. Double Suspension. For Wood Poles. 




FiG. 16. Double Suspension. For Iron Poles. 



TROLLEY WIMJE 8VSPMSIOIT. 



Tbe support of the trolley wire along straight lines 
is a simple matter and needs no explanation ; at 
curves and ends there have been some simple forms 
developed in practice that are handy to have at 
hand. Following are some of the points : 

Terminal ancliorag-e. —Single track. See 
Fig. 17. 

Line anchorag*e. — See Figs. 18 and 19. To be 
placed at the foot of all grades, at the top of hills, 
and at tangents, three (3) per mile is good practice ; 
where curves are frequent they will afford all the 
anchorage necessary. 




Fig. 17. 



444 



ELECTRIC STREET RAILWAYS. 




Fig. 18. Single Track. Fig. 19. Double Track. 

Turnout and Siding* Suspension. — Following is a sketch of a 
very simple arrangement of suspension and guys for a single-track turn-out. 




Fig. 20. 

Curves, Suspension, and Ours. — The suspension of the trolley wire 
at curves is complicated or simple, according as the track may be single or 
double, or the curve may be at a crossing or a simple curve. Below are 
sketches of several types of suspension for different forms of curves, for 
single and double track, for cross suspension, and for center-pole construc- 
tion. 




Fig. 21. Simple Right-angle 
Curve, Single Track. 



Fig. 22. Single Track, Obtuse Angle 





Fig. 23. Double Track, Right-angle 
Turn, Cross Suspension. 



Fig. 24. Double Track, Right- 
angle Turn, Center Pole. 



Crossing's, Suspension, and Ccurs. — Simple crossings of tracks 
make no complication in the suspension of the trolley wires. When curves 
are added to connect one track with the other, complications begin, and 



GUARD WIRES. 



445 



where double tracks cross double tracks, and each is connected to the other 
by curves each way, the network of trolley wires becomes very complicated. 
Following are sketches of a couple of simple crossings which will clearly 
enough illustrate the methods of suspension commonly used. 





Fig. 25. Single-Track Cross- Fig. 26. Single-Track Crossing, 
ing, Cross Suspension. Cross Suspension. 

GUARD WIRES. 

Where trolley wires are used in cities or in any location where there are 
other overhead conductors liable to fall across the trolley wire, it is custom- 
ary to place guard wires parallel with but above the trolley wire, as shown 
in the following sketch. A piece of No. 6 B. & S. galvanized iron or steel 




CROSS SUSPENSION WITH GUARDS 
FOR TROLLEY WIRE 



Fig. 27. 



wire is drawn taut above the regular suspension wire ; porcelain insulators 
are secured to the same at a point about a foot or 18 inches either side of the 
trolley wire, and through these insulators is threaded and tied a No. 10 gal- 
vanized iron wire. This guard should be broken at least every half-mile 
where it is in any great length, as it is not advisable to have it a continuous 
conductor for any great distance, and it is advisable to avoid its use wher- 
ever possible. 

IHTEHMISilKH OF MOST ECONOMICAL DEN- 
SITT OF CURRENT IN STREET RAIIWAT 
CONDUCTORS. 
(See Chapter on " Conductors," also paper by Mr. H. M. Sayers.*) 
Wherever there is danger of interference with other properties from elec- 
trolysis it is desirable to have the drop in rails quite low, the B.T. regula- 
* See Trans I. E. E. for July, 1900. 



446 ELECTRIC STREET RAILWAYS. 



tions being 7 volts between points on rails. This of course means track 
return feeders, and in some cases "negative boosters," or boosters on the 
track feeders. 

The formula was developed by Professor Perry from Kelvin's law, and 
following is Mr. Sayers's application of it to tramway work : — 

Formula for Determining- the Most Economical Current 
Density and Drop in Conductors for Tramway lines. 

R =r percentage or rate to be charged on complete cost of cables laid ready 
for use, representing interest and depreciation and maintenance, say 
7 per cent. 

Hours run per year, at 15 hours per day, for 365 days — 5475. 

w = number of watts continuously wasted in distributing system, that 

would cost one dollar per annum at a rate of 1.5 cents per k.w. hour. 

100 cents «„-.,„ . * A n 

= = 12.18 watts for one dollar. 

5475 x looo- 

p = cost of copper per ton of 2000 lbs. @ 30 c. per lb. laid complete ready 

for use = $600. 
m = tons (2000 lbs.) copper per mile for 1 square inch cross-section = 10.2 

tons. 
r =z resistance per mile of copper of 1 square inch cross-section=.0455 ohms. 
t = most economical drop per mile in volts. 

th n — J R - w -P- m - r _ J 1 X 12 - 15 X 6Q0 X 10.2 X .0155 . 

— V ioo - V ioo 

t = V236.8 = 15.39 volts per mile. 

t 15 39 

= * r= 338 amperes per square inch. 

It is obvious that the distance that the current can be transmitted at the 
economical density is limited by the permissible drop in the distributing 
system. The total drop is usually divided somewhat as follows, and is 
varied to suit conditions. 

Drop in feeders 50 volts. 

Drop in trolley 5 " 

Drop in track return 5 " 

Drop in return feeders (boosted) .... booster. 
Thus the distance over which an unboosted feeder will carry current with- 
out exceeding the drop is determined as follows : 

50 volts drop in feeder - .„ ., . x , . 

— — — : 1x . , rr- = 3 <25 miles, in this case. 

t = 15.3i volts drop per mile 
Where feeders are " boosted " it is necessary to introduce in the formula, 
the factors of the cost of the booster and its losses, changing the value of 
" w " and therefore that of " t," let 
a = cost per annum per k.w. for interest and depreciation on cost of 

booster, say $7.50. 
b = cost per annum for supplies and maintenance of booster, say $2.50, 
say the efficiency of the booster is 75 per cent, 

sb£is = w = *- 0W827 POT k -- h ™- 

100 

and w = t— ; — — — — - = 8.37 watts for 1 dollar per annum. 

Using the same values as in the first equation, 



/ 7 X 8.37 X 600 X 10.2 X .0455 ._ 

t = 4 / — jQQ — — = Vi63 = 12.76 volts per mile. 

t 1^ 76 

and =: -^— = 281 amperes per square inch as the most economical cur- 

.0455 .0455 
rent density for boosted feeders. 

Determination of the most economical drop, or limiting distance on the 
track maybe made by the above formulae, but calculations maybe expe- 
dited by use of a constant, as follows. Let 



HORSE-POWER OF ACCELERATION. 



447 



c = constant for ampere miles. 

n = resistance of track per mile, say .03 ohms. 

d = limit of drop permitted in rails, say 5 volts. Then 

c — — =-«-„ =166 ampere miles. 

Thus, if each car requires an average of 20 amperes the limit in miles of 
track for a drop of 5 volts would be for the above values, 166 -=- (20 x no. of 
cars, say 5) == 1.66 miles, provided all the cars were bunched at the end, or 
that one or two cars were ascending a heavy grade, requiring the same 
amount of current. To determine the greatest length of track that can be 
economically used without feeders, where cars are scattered along a line, 
the distances intervening between the power-house, or other power or feed- 
ing center, and each car, are multiplied by the amperes required per car, 
and the sum of these products must not exceed the value of " C" as follows : 
1 car .5 miles from power-house, 20 amperes c = 10 
1 " 1.5 " " " " 20 " c= 30 

1 " 3. " " " " 20 '• c= 60 

1 " 5. " " " " 20 c = 100 

Total C r: 200 
In this case c = 200, or more than the limit of 166 ; therefore the feeder 
point must be between the third and fourth cars, and the distance will be 
governed much by the grade between these points, for it is obvious that 
each of the above cars will take a much larger current than stated when 
ascending grades, and the value of this extra current must be carefully 
determined before making the calculations. 

HORiE-POWER Or ACCEIERATIOIT. 

The following diagram shows the power required to accelerate one ton, 
when running at any speed, to the next higher speed in miles per hour. 

HORSE-POWER EXERTED FOR EACH TIME. 
15 20 25 30 




Fig 



Copyrighted, 1901, by Charles Henry Davis. All rights reserved. 



448 



ELECTRIC STREET RAILWAYS. 



Power Curves. — For convenience in quickly ascertaining the horse- 
power required to propel a car of known weight under known conditions of 
speed and grade, the curves shown below have been calculated. 

The quantities which the various lines represent are clearly marked in 
the cut, but for the benefit of those who may be unfamiliar with such dia- 
grams, the following explanation is inserted : The left-hand portion of the 
lower horizontal line represents the speed in miles per hour ; the right-hand 
portion of same line, the h. p. per car ; the oblique lines in left-hand side of 
cut, the per cent grade as marked on each line ; the oblique lines on right- 
hand side of cut, the weight of car as marked ; while the vertical line in 
centre of cut represents the h. p. per ton. 













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HORSE-POWER OF TRACTION. 



449 



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Wn 
H. P. =-^rz- (iT+2000 sin 0). WrrLoad in tons. « = Speed in miles per hour, 

' K 
= Wn X .0026f (K ± 2000 sin 0). K— Resistance in lbs. per ton. K'=— 

Rz= Constants of power required to move one ton on level at speeds in 

table with K— 10. 
R'= Constants of additional power required to raise one ton on 

grades and at speeds given. 
R~X WK'z=~K. P. required on levels alone for speeds given. 
H'x TF:=H. P. additional on grades alone for speeds and % given. 
W(K'R± Rf) = total H. P. required. 

Example : Given a motor car, total weight 9 tons, to ascend a 7 per 
cent grade at a speed of six miles per hour. "What is the estimated horse- 
power required, with K= 30 lbs.? 



450 



ELECTRIC STREET RAILWAYS. 



30 
If for 6 miles per hour is .16, which, multiplied by 9 x^.,== 4.32 h. p., in 

overcoming the track resistances alone. 

#'=2.240, which, multiplied by 9, = 20.16. The sum of the two will give 
the total theoretical, i.e., 24.48 h. p. required. Allowing 50 per cent as the 
combined efficiency of motors and gearing, to operate this car would require 
a draft of 48.96 h. p. upon the line. 





HORiE - POWEB 


OF TRACTION. 


(Davis.) 




6 
1 


Speed in Miles per Hour. 


O 




























"3 
o 


4 


6 


8 


10 


12 


15 


20 


25 


30 


35 


40 


50 


60 


Horse-Power Required to Propel One Ton at Various Speeds up 


Ph 


Various Grades. 





.32 


.48 


.64 


.80 


.96 


1.20 


1.60 


2.00 


2.40 


2.80 


3.20 


4.00 


4.80 


1 


.53 


.80 


1.07 


1.33 


1.60 


2.00 


2.66 


3.33 


4.00 


4.66 








2 


.74 


1.12 


1.49 


1.87 


2.24 


2.80 


3.63 


4.66 


5.60 










3 


.93 


1.44 


1.92 


2.40 


2.88 


3.60 


4.80 


6.00 












4 


1.17 


1.76 


2.34 


2.93 


3.52 


4.40 


5.47 














5 


1.39 


2.08 


2.77 


3.46 


4.16 


5.20 
















6 


1.60 


2.40 


3.20 


4.00 


4.80 


















7 


1.88 


2.72 


3.62 


4.53 




















8 


2.02 


3.04 


4.05 






















9 


2.24 


3.36 


4.48 






















10 


2.47 


3.68 


4.90 






















11 


2.67 


4.00 
























12 


2.88 


4.32 
























13 


3.09 


























14 


3.29 


























15 


3.52 



























Note No. 1. — The h. p. required to propel a car equals the total weight 
of car plus its load (in tons) multiplied by the h. p. in table corresponding 
to assumed grade and speed. 

iTREET RAILWAY. 
Tractive Force. 

F. E. Idell, M. E. 

On Good Track. -To start car 116 lbs. per ton. 

To keep in motion at 6 miles per hr. 15.6" " " 

On Bad Track. —To start car 135 " " " 

To keep in motion 32 " " " 

On Curves. — To start car from to 6 miles per hour . 284 " " " 
average, 264 feet per minute. 

APPROXIMATE INDICATED HORiE - POTTER. 
PER CAR. (Dawson.) 



Numbei 


Cars. 


1 


to 


5 


5 


" 


10 


10 


" 


15 


15 


" 


25 


25 


" 


50 



I. H. P. 



I. H. P. per car in large city systems varies from 18 to 23. 



TRACTION. 



451 



TRACTION. 

(Davis.) 







Load of Trailer Cars in Tons which a Motor 


Per cent 
Grade. 


Tractive Force 
in Pounds 
per Ton. 


Car of one Ton will Haul. 












Snowy Pail. 


Wet Rail. 


Dry Rail. 





30 


8.50 


12.33 


16.00 


1 


50 


4.70 


7.00 


9.00 


2 


70 


3.07 


4.21 


6.14 


3 


90 


2.17 


3.44 


4.55 


4 


110 


1.60 


2.63 


3.54 


5 


130 


1.19 


2.07 


2.84 


6 


150 


0.90 


1.66 


2.33 


7 


170 


0.70 


1.35 


2.00 


8 


190 


0.50 


1.10 


1.63 


9 


210 


0.35 


0.90 


1.38 


10 


230 


0.24 


0.74 


1.17 


11 


250 


0.14 


0.60 


1.00 


12 


270 


0.05 


0.48 


0.85 


13 


290 


Wheels slip. 


0.38 


0.77 


14 


310 




0.30 


0.61 


15 


330 










0.21 


0.51 


16 


350 










0.14 


0.43 


17 


370 










0.08 


0.35 


18 


390 










0.02 


0.28 


19 


410 










Wheels slip. 


0.'/2 


20 


430 












0.16 


21 


450 












0.11 


22 


470 












0.06 


23 


490 












Wheels slip. 



Note No. 1. — Multiply figures in table by weight of motor car (in tons) 
to get weight of trailer (in tons) that said motor car will haul up corre- 
sponding grades. 

REVOlVTIOKi PER MINUTE OF VARIOUS SIZED 
WHEELS TO MAKE VARIOUS SPEEDS. 





Miles per Hour. 




2 


4 


6 


8 


10 


15 


20 


25 


30 


40 


Diameter 






















of 

Wheel. 














































I 


^eet per Minute. 










176 


352 


528 


704 


880 


1320 


1760 


2200 


2640 


3520 


24 in. 


28 


56 


84 


112 


140 


210 


280 


350 


420 


560 


26 in. 


26 


52 


78 


103 


129 


194 


258 


323 


388 


517 


28 in. 


24 


48 


72 


96 


120 


180 


240 


300 


360 


480 


30 in. 


22 


45 


67 


90 


112 


168 


224 


280 


336 


448 


33 in. 


20 


41 


61 


82 


102 


153 


204 


255 


306 


408 


36 in. 


19 


37 


56 


75 


93 


140 


187 


234 


280 


374 


42 in. 


16 


32 


48 


64 


80 


120 


160 


200 


240 


320 



452 



ELECTRIC STREET RAILWAYS. 



TRACTIOHT. 

Theoretical Horse-Power per Ton of 3000 MAh*. and per 

Jflile per Hour with Various Grades and 

Coefficients of Traction. 

(Merrill.) 





Coefficient of Traction. 


o 


12 


13.5 


15 


18 


20 


25 


30 


35 


40 


50 


60 





.032 


.036 


.04 


.048 


.054 
.10* 


.06* 


.08 


.094 


.10* 


.134 


.16 


1 


.0854 


.0891 
.142* 


.09+ 


.1014 


.12 


.134 


.14* 


.16 


.18* 


.214 


2 


.138* 


.14* 


.154* 


.16 


.174 


•18* 


.20 


.214 


.24 


.264 


3 


.192 


.196 


.20 


.208 


.214 


.22* 


.24 


'.3& 


.26* 


.294 


.32 


4 


.2454 


.2494 
.302| 


•254 
.30| 


.2614 


.26* 


.28 


.294 


.32 


.34* 


.374 


5 


.298| 


.314^ 


.32 


.334 


.34* 


.36 


.374 


.40 


.42* 


6 


.352 


.356 


.36 


.368 


.374 


.38* 


.40 


AU 


.42* 


•454 


48 


7 


.4054 


.4094 


.414 


.4214 


•42* 


.44 


.454 


.46* 


.48 


.50* 


.534 


8 


.4584 


Am 


.46* 


•474* 


.48 


•494 


.50* 


.52 


.534 


.56 


.58* 


9 


.512 


.516 


.52 


.528 


.534 


•54* 


.56 


.574 


.58* 


•614 

.66* 


.64 


10 


.5654 


.5694 


•574 
.62* 


.5814 


.58* 


.60 


.614 


.624 


.64 


■694 
•74* 


11 


.618§ 


.6224 


.634* 


.64 


.654 


.66* 


.68 


.694 


.72 


12 


.672 


.676 


.68 


.688 


.694 


.70§ 


.72 


.734 
.78* 


.74* 


.774 


.80 


13 


.7251 


.729^ 


.734 


.7414 


.744 


.76 


•774 


.80 


•82* 


.854 


14 


.778| 


.782* 


.78* 


.794^ 


.80 


.814 


.82* 


.84 


.854 


.88 


.90* • 


15 


.832 


.836 


.84 


.848 


.854 


.86* 


.88 


.894 


.90* 


•934 


.96 



H.P. = .002* [K+ (20 x % grade)]. 

HORSE-POWER. §PEED, MD HORIZONTAL 
EEJFOJRT II POUNDS. 





Miles Per Hour. 


Mech. 


2 


4 


6 


8 


10 


15 


20 


25 


30 


40 


H. P. 








Feet 


Per Minute. 










176 


352 


528 


704 


880 


1320 


1760 


2200 


2640 


3520 




lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


2 


375.0 


187.0 


125.0 


93.7 


75.0 


50.0 


37.5 


30.0 


25.0 


18.7 


4 


750.0 


375.0 


250.0 


187.5 


150.0 


100.0 


75.0 


60.0 


50.0 


37.5 


6 


1125.0 


562.0 


375.0 


281.2 


225.0 


150.0 


112.5 


90.0 


75.0 


56.2 


8 


1500.0 


750.0 


500.0 


375.0 


300.0 


200.0 


150.0 


120.0 


100.0 


75.0 


10 


1875.0 


937.0 


625.0 


468.7 


375.0 


250.0 


187.5 


150.0 


125.0 


93.7 


15 


2812.0 


1406.0 


937.0 


703.1 


562.5 


375.0 


281.2 


225.0 


187.5 


140.6 


20 


3750.0 


1870.0 


1250.0 


937.2 


750.0 


500.0 


375.0 


300.0 


250.0 


187.5 


25 


4687.0 


2343.0 


1562.0 


1172.0 


937.5 


625.0 


468.7 


375.0 


312.5 


234.3 


30 


5625.0 


2812.0 


1875.0 


1406.0 


1125.0 


750.0 


562.5 


450.0 


375.0 


281.2 


40 


7500.0 


3750.0 


2500.0 


1875.0 


1500.0 


1000.0 


750.0 


600.0 


500.0 


375.0 


50 


9372.0 


4687.0 


3125.0 


2344.0 


1875.0 


1250.0 


937.5 


750.0 


625.0 


468.7 



POWER REQUIRED FOR TRUCK CARS. 



453 



POWER REQIIRED FOR DOUBLE AXn KIXttUE 

truck: CARS. 
Wattmeter placed on car. (McCulloch.) 





CO 

CD 
bD 

c3 

0> 
< 


CD 

ft 

CO 

u 
o , 

"el S 

> 


CD o 

CD CD 

u n 


% 

CD 
CD 

a . 
->> 

CO -J 

£'y 

c3 o3 

cdO 

&c 

S3 

CD 

> 


o 
H 

.So. 

1! 

CD g 

c3 

s 

< 


Average Watt-hours per 

Cai Mile per 1000 

Passengers. 


Double-truck car. Seats 
36 ; weight, 11.75, tons ; 
average for entire day 


12040 


1334 


9.03 


335 


1025 


5.9 


Same as above. Average 
for heaviest trip . . . 


13080 


1412 


9.25 


335 


1025 





Single-truck car, no 
' trailer. Seats 28; 
weight, 8 tons .... 


8471 


921 


9.20 


303 


1060 





Single-truck car. Trail- 
ers operated 26% of the 
time. Average for the 
entire day 


9400 


1110 


8.42 


254 


108S 


7.9 


Single-truck motor and 
open trailer. Seats, 
63; weight, 10.5 tons. 
Average for heaviest 
trip 


12680 


1440 


8.84 


201 


1208 






HORIZONTAL EFFORT EXERTED OUT CURVES. 
founds Per Ton. 









Radius 


of Curvature — 


Feet. 






Length of 


















Wheel 


















Base,Feet. 


25 


30 


40 


50 


60 


70 


80 


100 


3.5 


88.6 


73.9 


55.4 


44.3 


36.9 


31.7 


27.7 


22.2 


4 


94.0 


78.4 


58.8 


47.0 


39.2 


33.6 


29.4 


23.5 


4.5 


99.4 


82.9 


62.2 


49.7 


41.4 


35.5 


31.1 


24.9 


6 


115.6 


96.4 


72.3 


57.8 


48.2 


41.3 


36.1 


28.9 


6.5 


121.0 


100.9 


75.7 


60.5 


50.4 


43.2 


37.9 


30.3 


7 


126.4 


105.4 


79.0 


63.2 


52.7 


45.2 


39.5 


31.6 



Assumed — 3 miles per hour speed on curve, 4 ft. 8£ in. gauge. 



454 



ELECTRIC STREET RAILWAYS. 



Formula from Moiesworth : 

Let W = weight on wheels in lhs. 

A'= coefficient, in this case .27. 

G = gauge of track = 4/ — 8-J" = feet. 

B = rigid wheel hase in feet. 

Ii =z radius of curves in feet. 
Then 

Tractive force or resistance per ton =r — -^ — ^Z — I 



HOAIZOHIAI I IHMII OX GRADES. 
Pounds per Ton. 









Speed 


— Miles per 


Hour. 






Grade. 


















Per Ct. 
























2 


4 


6 


8 


10 


12 


14 


16 


18 


20 





15.03 


15.11 


15.24 


15.42 


15.66 


15.95 


16.29 


16.69 


17.14 


17.64 


1 


35.03 


35.11 


35.24 


35.42 


35.66 


35.95 


36.29 


36.69 


37.14 


37.64 


H 


45.03 


45.11 


45.24 


45.42 


45.66 


45.95 


46.29 


46.69 


47.14 


47.64 


2 


55 03 


55.11 


55.24 


55.42 


55.66 


55.95 


56.29 


56.69 


57.14 


57.64 


2i 


65.03 


65.11 


65.24 


65.42 


65.66 


65.95 


66.26 


66.69 


67.14 


67.64 


3 


75.03 


75.11 


75.24 


75.42 


75.66 


75.95 


76.29 


76.69 


77.14 


77.64 


3£ 


85.03 


85.11 


85.24 


85.42 


85.66 


85.95 


86.29 


86.69 


87.14 


87.64 


4 


95.03 


95.11 


95.24 


95.42 


95.66 


95.95 


96.29 


96.69 


97.14 


97.64 


5 


115.03 


115.11 


115.24 


115.42 


115.66 


115.95 


116.29 


116.69 


117.14 


117.64 


6 


135.03 


135.11 


135.24 


135.42 


135.66 


135.95 


136.29 


136.69 


137.14 


137.64 


7 


155.03 


155.11 


155.24 


155.42 


155.66 


155.95 


156.29 


156.69 


157.14 


157.64 


8 


175.02 


175.11 


175.24 


175.42 


175.66 


175.95 


176.29 


176.69 


177.14 


177.64 


9 


195.03 


195.11 


195.24 


195.42 


195.66 


195.95 


196.29 


196.69 


197.14 


197.64 


10 


215.03 


215.11 


215.24 


215.42 


215.66 


215.95 


216.29 


216.69 


217.14 


217.64 



APPROXIMATE CTURREXT COUfSUMPIIOHf PER 

CAR. 

Two 25-H.P., S. R. G. Motors. 



Diameter 
Wheels. 
Inches. 






Horizontal Effort - 


-Pounds. 


100 


200 


400 


600 


800 


1000 


1200 


1400 






30 
33 


25.8 
26.6 


32.8 
34.0 


44.6 
47.0 


54.6 
57.6 


63.8 
67.4 


72.6 
77.6 


82.6 
88.4 


92.0 
98.2 







Two 30-M.P., S. R. G. Motors. 



Diameter 
Wheels. 
Inches. 






Horizontal Effort — 


Pounds. 






100 


250 


500 


750 


1000 


1250 


1500 


2000 


2500 


3000 


30 
33 


28.6 
29.4 


38.8 
40.0 


51.4 63.0 
54.0 65.8 


73.2 
77.0 


84.2 
88.8 


93.4 
98.8 


111.8 
119.2 


130.0 
138.4 


147.6 
158.0 



AXLE SPEED. 



455 



4.AJLE SPEED PER CAR WITH DOUBLE MOTOB 
EftVIPME]¥T - RE V§. PER MAHXTTE. 

Average of Several Types 25-HC.P. notorx. 


Diameter 
Wheels. 
Inches. 


Horizontal Effort — Pounds. 


100 


200 


400 


600 


800 


1000 


1200 


1400 






30 
33 


308 
300 


253 

248 


195 

189 


170 
165 


153 
149 


141 
136 


131 
126 


122 
119 







Average of Several Types of 30 H. P. UEotors. 



hameter 






Horizontal Effort — 


Pounds. 






nches. 


100 


250 


500 


750 


1000 


1250 


1500 


2000 


2500 


3000 


30 
33 


282 

272 


260 
252 


202 
194 


173 

166 


153 
148 


139 
134 


130 
125 


117 
113 


107 
103 


100 

95 



Brniula for close appi'oximation of current required to propel a given car. 
]». tons in train x [( (% grade -j- 1) 20) + (curve resistance per ton)] = 
Ponds Horizontal Effort. 



W« ©E CARS ©]¥ TEW MAEES OE TRACK, VARI- 
OUS SPEEDS AID HEADWAYS. 



Miutes 
Aart 


Average Speed in Miles per Hour. 


n- 






















Hlway. 


6 


7 


8 


9 


10 


12 


15 


20 


25 


30 


1 


100 


86 


75 


67 


60 


50 


40 


30 


24 


20 


2 


50 


44 


38 


33 


30 


25 


20 


15 


12 


10 


3 


33 


29 


25 


22 


20 


17 


13 


10 


8 


7 


4 


25 


22 


19 


14 


15 


13 


10 


8 


6 


5 


5 


20 


17 


15 


13 


12 


10 


8 


6 


5 


4 


6 


17 


14 


13 


11 


10 


8 


7 


5 


4 


3 


7 


14 


12 


11 


10 


9 


7 


6 


4 


3 


3 


8 


13 


11 


9 


8 


8 


6 


5 


4 


3 


3 


10 


10 


9 


8 


•7 


6 


5 


4 


3 


2 


2 


15 


7 


6 


5 


4 


4 


3 


3 


2 


2 


1 


10 


5 


4 


4 


3 


3 


3 


2 


2 


1 


1 


50 


3 


3 


3 


2 


2 


2 


1 


1 


1 


1 



Ncte. — Fractions above one-half are considered whole numbers, and 
f radons below one-half are neglected. 



456 



ELECTRIC STREET RAILWAYS. 



To obtain the number of cars required to operate any length road, divie 
the number found in the table under the desired average speed and hea- 
way by ten, and multiply by the length of the road in question. Should t 



PRESSURE IN POUND PER SQUARE FOOT OF CROSS SECTION. 




Fig. 30. 



Effect of Shape of Moving Body on Air Resistance," Crsby's 
Experiments. 



be desired to run at different average speeds on various portions of the-oad, 
treat each portion as a separate road, and add the results together. 1> the 
number of cars thus obtained should be added 20 per cent for resere for 
roads under 20 cars. For roads over 20 cars, 10 per cent reserve wU be 
enough 



EATING STREET-RAILWAY MOTORS. 



457 



Formula : — 
Let n = number of cars required. 

to = miles of track. 

S = average speeds in miles per hour. 

/= interval or headway in minutes. 
Then, to X 60 



HEADWAY, NI>EEI>, AUTR TOTAL Xl'mtER ©E 
CARS. 



Total number of cars on a given length of street on which cars are run- 
ning both ways = (length of street X 120) -f- (headway in minutes x speed 
ir. miles per hour). 



MIEEjS PER HOUR I]¥ FEET PER HIIUTE 
AID PER SECOND. 



(Merrill.) 



Miles 


Feet 


Feet 


Miles 


Feet 


Feet 


per 


per 


per 


per 


per 


per 


Hour. 


Minute. 


Second. 


Hour. 


Minute. 


Second. 


1 


88 


1.46 


16 


1408 


23.47 


2 


176 


2.94 


17 


1496 


24.93 


3 


264 


4.4 


18 


1584 


26.4 


4 


352 


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44 



RATING IIREET-RAIIWAY MOTORS. 



(Condensed from W. B. Potter in Street Railway Journal.) 

Rise of temperature after one hour's run under rated full load not to ex- 
ceed 75° C. ; room being assumed at 25° C. Average load for a day's run 
should not exceed 30 per cent of its rated full load, which will give a rise of 
temperature of about 60° C. 

Tie above ratings are based on aline potential of 500 volts, but the aver- 
age performance can generally be increased in proportion to the increase in 
line voltage ; that is, a motor will do approximately 10 per cent heavier 
service for the same temperature rise when operated at 550 volts. 

With electric brakes, motors must have increased capacity, as heating 
increases 20 to 25 per cent. The 20 per cent increase is on roads having few 
graces and stops, while the 25 per cent is on hilly roads with frequent stops. 

Approximate rated horse-power of motors == 
(total weight of car in tons) x (max. speed in miles per hour on level). 



458 ELECTRIC STREET RAILWAYS. 



For equipments with electric brakes, divide by 4 instead of 5. "Whei 
maximum speed is not known, it may be assumed as twice the schedul* 
speed. 

Example 1: 

20 ton car (loaded) x 50 m. p. b. nn , „„ , 

i ' = = 200 b. p., or four 50 b. p. motors. Ii 

tbis case, if tbe line pressure were raised to 600 volts, electric brakes couli 
be used on tbe equipment by cbanging tbe gear ratio so as to bave tbe samj 
maximum speed. 

Example 2 : 

11 ton car (loaded) x 25 m. p. b. „ K ,_ M , 

— _— ^ — = 55 b. p., or two 30 b. p. motors, 

These rules indicate minimum capacity under ordinary conditions. 
Tractive Effort. 

Tractive effort is dependent on the rate of acceleration, grade, car fric- 
tion, and air resistance, which latter is ordinarily included in friction. 
Acceleration is expressed in miles an hour per sec. 1 mile per hour per s<c. 
= 1.466 feet per sec. Excluding car friction, a tractive effort of 92J lbs. per 
ton (2000) will produce an acceleration of 1 mile per hour per 6ec. on a le^el 
track, and the rate of acceleration will vary in direct proportion to tbe 
amount of tractive effort. On ordinary street cars, tractive effort during 
acceleration often rises to 200 or 300 lbs. per ton. 

On elevated or suburban roads the maximum tractive effort is generally 
100 to 150 lbs. per ton. For heavy freight work with slow speeds, the trac- 
tive effort seldom exceeds 30 to 40 lbs. per ton. 

Grades are commonly expressed in percentage of feet rise in 100 fee - of 
distance, and tractive effort for a grade is the same percentage of the 
weight to be drawn as the rise is of the length of 100 feet. For instance, 
the tractive effort for a weight of one ton (2000 lbs.) up a grade of 3 per 
cent would be 3 per cent of 2000 lbs., or 60 lbs. For the total tractive effort 
there must be added to this, tbe effort for overcoming the car, wind, and 
rolling friction on a level. 

Maximum tractive efforts from numerous tests are shown in the folbwing 
table : 

Tractive effort in 
lbs. per ton. 

15 ton car, up to 25 m. p. b 25 

" " " " " 50 " » " 50 

25 " " " " 25 " " " 20 

" " " " " 50 " '" " 25 

100 " train " " 25 " " " 15 

Heavy freight train up to 25 m. p. b. 6 to 10. 

The above figures have to be increased for snow and ice on tbe track 
Tractive Coefficient. 

This coefficient is usually expressed as the ratio between the weiglt on 
tbe driving-wheels and the tractive effort, and varies largely with the con- 
dition of the rails. 

In train work, tbe weight on drivers should be six times the tractive 
effort. 

Example:— Required the weight of a locomotive to draw a 100-ton 
train up a 2 per cent grade. 
For train. 

100 tons X 15 lbs. for friction = 1500 lbs. 
" " x 40 " " grade =4000 " 

5500 lbs. 



RATING STREET-RAILWAY MOTORS. 459 



Assume a 20-ton locomotive. 

20 tons x 15 lbs. for friction = 300 lbs. 
20 " X 40 " " grade = S00 " 

Total tractive effort, 6600 lbs. 

6600 lbs. equals 16.5 per cent of 20 tons, or a tractive coefficient of 16.5 per 
cent. Starting the train on a 2 per cent grade with acceleration of J m. p. h. 

92.3 
per sec. would mean additional tractive effort equivalent to — - =30.8 lbs. 

per ton. 

This would add to the requirements as follows : 

Train 100 tons, for friction and grade as above . . . 5500 lbs. 
" " " at 30.8 lbs. for acceleration 3080 ." 

Total for train 8580 lbs. 

Assume 35-ton locomotive with motors on all axles. 

35 tons at 15 lbs. for friction 525 lbs. 

" " " 40 " " grade 1400 " 

" " " 30.8 for acceleration 1078 " 



Total tractive effort . . . 11583 lbs. 

or a tractive coefficient of 16.5 per cent for the 35-ton locomotive. 
Tests show the following tractive coefficients : 

Sanded 
per cent. per cent. 

Dry rail 28 30 

Thoroughly wet rail 20 25 

Greasy moist rail . 15 25 

With ice and snow on the track, the coefficient is lower, and the rolling- 
friction higher. 

Arerag-e energy. — Approximate capacity of a power station may be 
assumed as about 100 watt-hours per ton mile of schedule speed for ordinary 
conditions of city and suburban service. 

Example : — 15-ton car, 12 miles per hour schedule, 
k.w. at stations 100 X 15 X 12 = 18 k.w. 

If stops are a mile or more apart, only 60 to 70 watt-hours may be neces- 
sary. 

Frequent stops and high schedule speeds take 120 or more watt-hours. 

The following table of efficiencies will be found convenient in estimating 
the power required for operation of motor cars, using three-phase trans- 
mission and direct current motors. The efficiencies would vary somewhat 
with the load factor, but can be taken as generally applicable. 

Considering the I.H.P. of the engine as a basis, for the 

Average efficiency of engine 90 per cent. 

" generator 94 " " 

" high potential lines .... 95 " " 

" substations 90 " " 

" direct current lines .... 92 u " 
" motors, including losses of 

control 72 " " 

Combined efficiency of the motors and series parallel 
control during period of cutting out tbe controller 

may be taken as 63 " " 

Efficiency of motors after cutting out the controller, 
depending on size of motors 80 to 85 per cent. 



460 



ELECTRIC STREET RAILWAYS. 



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WEIGHT OF TRUCKS. 465 

APPROXIMATE WEIGHT! OF TRUCKS. 



Kind. 


Weight. 




3500 lbs. 




2600 " 




3900 " 




1500 " 




3700 " 


Running gear 


1500 " 



TORdUE ASH HORSE-POWER. 



H. P. 


per Lb. Applied at Periphery at 100 Rev. per Min. 


Diameter 
Wheel. 


26" 


28" 


30" 


33" 


36" 


H. P. 


.02062 


.02221 


.0238 


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Pounds at Periphery per H. 


P. at 100 Rev. per Min 




Diameter 
Wheel. 


26" 


28" 


30" 


33" 


36" 


Lbs. 


48.481 


45.018 


42.017 


38.197 


35.014 



Lbs. 



126050.9 X H. P. 



Diam. x Rev. 

H. P. = .00000793 X diam. wheel x rev. x lbs. at periphery. 
H. P. per lb. at periphery at one mile per hour = .002867. 
Lbs. at periphery per H. P. at one mile per hour = 374.9. 

Hote on Emerg-ency Braking- of Cars. 

In case of emergency, motormen often reverse the motors, which brings 
the car up with a severe jerk, and is quite apt to strip gears. This is 
not necessary, and should never be done unless the canopy switch is first 
thrown off, then when the motors are reversed and the controller handle 
thrown around to parallel, the motors will act as generators and will bring 
the car to an easy stop with no harm to the apparatus. In case circuit 
breakers are used in place of the plain canopy switches, the reversal of the 
motors will draw so much current from the line that the circuit breakers, 
if properly adjusted, will open the circuit and the controller can then be 
used as suggested above. 

COPPER WIRE EUSES EOR RAILWAY CIRCUITS. 



B. &S. 

Gauges. 


17 


16 


15 


14 


13 


12 


11 


10 


9 


8 


7 


Fuse Point 

in 
Amperes. 


100 


120 


140 


166 


200 


235 


280 


335 


390 


450 


520 



466 



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ELEVATED RAILWAY TRAIN PERFORMANCE. 471 



DIMENSIONS Of iTAIVDARD - PECKHAM 
TRACKS. 



Style. 



8 Standard, for open cars 
8A " " " 

9 A Extra long, for open 

cars 

7 D Excelsior .... 

7B " 

7A " 

7 Excelsior trailer truck 

Extra strong storage bat- 
tery 

Extra long, with regular 
and emergency brake 

Extra long, with track 
brake 

Electric mining truck . 



Lengths 



Top 
Erame. 



14 ft. 
14 « 

16 " 

116." 
13 "' 
13 " 
Il3 " 



9 in 
9 " 



Spring 
base. 



13 ft. 2 in, 

13 " 2 " 

14 " 6 " 
16 " " 
13 " " 

13 " " 
12 " 6 " 

14 " 6 " 
14 " 6 " 

14 " 6 " 



Wheel 
Base. 



7 in. 

7 " 



7 ft. 



ft. 6 in. 



Height of 
Truck. 



30 in. 
Wheels. 



27£ " 



Weight 
Complete 
Pounds. 



5000 
4500 
4000 



5000 
5000 



5000 
4500 



Note on Motors. 

It had been the author's intention to include in this chapter cuts and di- 
mensions of the standard motors and generators ; but it was found that the 
standards changed so rapidly, and practice demanded so many and diversi- 
fied forms of motor and equipment, that it was impracticable to include 
such cuts without danger of misleading the engineer. 

ELEVATED RAILWAY TRAI9T PERFORMANCE. 

(S. H. Short.) 
Data Sheet of Train Ko. 1. 

Elevated Railway Service 

Number of cars in train 3 

Full speed of train on level track (miles per hour) . . 31 

Average speed, stops one-third mile apart (miles per 

hour) 16.5 

Motor Car. 

Weight of motor car body 10 Tons. 

Weight of both trucks 10 " 

Weight of two motors 7 " 

Weight of seventy-five passengers 5_ " 

Total weight of loaded motor car 32 " 

Number of motors on motor car 2 " 

♦Commercial rated power of each 200 H.P. 

Safe constant load for each 100 " 

Safe temporarv tractive effort of equipment 10,000 Lbs. 

Safe constant tractive effort of equipment 3,500 " 

Weight on drivers 19.5 Tons. 

Ratio of weight on drivers to total weight ^26% 

Adhesive power 9,750 Lbs. 

Ratio of safe temporary tractive effort to adhesion .... 100% 

Ratio of safe constant tractive effort to adhesion 36% 

* This motor will deliver the commercial rated output for one hour with- 
out heating more than 75° C. above the surrounding air. 



472 



ELECTRIC STREET RAILWAYS. 



Complete Train. 

Total weight of loaded motor car 

Weight of two coaches 

Weight of 150 passengers in coaches 

Total weight of loaded train 

Maximum horizontal effort in accelerating train 

Horizontal effort per ton during acceleration 

Maximum power in accelerating uniformly to full speed . . 
Maximum current at 500 volts accelerating train uniformly 

to full speed • ■ • • ■ • •- 

Time required in accelerating uniformly to full speed . . . 

Distance in which train will acquire full speed 

Horizontal effort, train running uniform speed 

Power consumed, train running uniform speed 

Tractive effort per ton ■ • ■ • ■ ■ • ■ ■ 

Maximum practical negative horizontal effort in braKing 

Time required to bring train to full stop 

Distance traversed by train during braking 

Train Performance. 



32 


Tons. 


32 


" ■ 


10 


" 


74 


" 


9,750 


Lbs. 


132 


" 


412 


H. P 


780 


Amp. 


34 


Sec. 


900 


Ft 


1,300 


Lbs. 


106 


H. P 


18.25 Lbs 


13,800 


" 


16 


Sec 


370 


Ft 



Track. 


Horse 
Power. 


Current at 
500 Volts. 


Speed Miles 
per Hour. 


Horizontal 
Effort. 


Level . . . 
1% grade . . 
2% grade . . 
3% grade . . 


106 
170 

235 

295 


190 amperes. 

290 

400 " 

505 


32 
22 
20.8 
19 


1300 lbs. 
2780 " 
4260 " 
5740 " 



Data Sheet of Train ]*©. 2. 
Character of Service ; Elevated Railway. 

Number of cars in train ■ • • • ■ 2 

Full speed of train on level track (miles per hour) . . 31 

Average speed, stops one-third mile apart 15.8 

Motor Car. 

Weight of motor car body 10 Tons. 

W T eight or both trucks 1U ^ 

Weight of two motors 5.5 ^ 

Weight of 75 passengers _2_ 

Total weight of loaded motor car 30.5 

Number of motors on motor car J p 

♦Commercial rated power of each 1^ ,f ' 

Safe constant load for each «0 

Safe temporary tractive effort of equipment 5,ww L,r>s. 

Safe constant tractive effort of equipment I,b00 

Weight on drivers • •. • q£<y 

Ratio of weight on drivers to total Aveight &>% 

Adhesive power • • '• • : 'wor 

Ratio safe temporary tractive effort to adhesion bi% 

Ratio safe constant tractive effort to adhesion it>A> 

Complete Train. 

Total weight of loaded motor car 30.5 Tons. 

Weight of one coach x * u 

Weight of 75 passengers in coach J?_ 

* This motor will deliver the commercial rated output for one hour with- 
out beating more than 75° C. above the surrounding air. 



ELEVATED RAILWAY TRAIN PERFORMANCE. 



473 



Maximum horizontal effort in accelerating train 5,640 Lbs. 

Horizontal effort per ton during acceleration 109 " 

Maximum power in accelerating uniformly to full speed . . 280 H. P. 
Maximum current at 500 volts accelerating uniformly to full 

speed 500 Amp. 

Time required in accelerating uniformly to full speed . . . 37.5 Sec. 

Distance in which train will acquire full speed 953 Ft. 

Horizontal effort, train running uniform speed 1,000 Lbs. 

Power consumed, train running uniform speed 115 H. P. 

Tractive effort per ton, train running uniform speed . . .. 19.7 Lbs. 

Maximum practical negative horizontal effort in braking . . 11,000 Lbs. 

Time required to bring train to full stop 16 Sec. 

Distance traversed by train during braking 390 Ft. 

Train Performance. 



Track. 


Horse 
Power. 


Current at 
500 Volts. 


Speed Miles 
per Hour. 


Horizontal 
Effort. 


Level . . . 
1% grade . . 
2% grade . . 
3% grade . . 


92 
135 
176 
220 


175 amperes 

250 

320 " 

390 


31 
24.8 
21.3 
19.9 


1,013 lbs. 
2043 " 
3073 " 
4103 " 



Data Sheet of Train ]fo. 3. 
Elevated Railway Service. 

Number of cars in train 1 

Full speed of train on level track (miles per hour) . . 26 
Average speed, stops one-third mile apart (miles per 

hour) 15 

Motor Car. 

Weight of motor car body 10 Tons. 

Weight of both trucks 10 " 

Weight of two motors 3.5 " 

Weight of 75 passengers 5 " 

Total weight of loaded motor car "2875 " 

Number of motors on motor car 2 

♦Commercial rated power of each 60 .H.P. 

Safe constant load for each 25 " 

Safe temporary tractive effort of equipment 3,300 Lbs. 

Safe constant tractive effort of equipment • . 700 " 

Weight on drivers 16 Tons. 

Ratio of weight on drivers to weight 56% 

Adhesive power 8,000 Lbs. 

Ratio safe temporary tractive effort to adhesion 41% 

Ratio safe constant tractive effort to adhesion 8% 

Complete Train. 

Total w eight of loaded train 28.5 Tons. 

Maximum horizontal effort in accelerating train 2,600 Lbs. 

Horizontal effort per ton during acceleration 91.5 " 

Maximum power in accelerating uniformly to full speed . . 122 H.P. 
Maximum current at 550 volts, accelerating uniformly to full 

speed 220 Amp. 

Time required in accelerating uniformly to full speed . . . 36.5 Sec. 

Distance in which train will acquire full speed ...... 810 Ft. 

Horizontal effort, train running uniform speed 712 Lbs. 

Power consumed, train running uniform speed 51 H.P. 

* This motor will deliver the commercial rated output for one hour with- 
out heating more than 75° C. above the surrounding air. 



474 



ELECTRIC STREET RAILWAYS. 



Tractive effort per ton, train running uniform speed 
Maximum practical negative horizontal effort in braking 

Time required to bring train to full stop 

Distance traversed by train during braking 



25 


Lbs 


5,300 


" 


14.5 


Sec 


305 


Ft 



Train Performance. 



Track. 


Horse 
Power. 


Current at 
500 Volts. 


Speed Miles 
per Hour. 


Horizontal 
Effort. 


Level . . . 

1% grade . . 
2% grade . . 
3% grade . . 


51 
68 
85 
101 


90 amperes. 
124 " 
154 " 

182 


26 
19.9 
17.2 
15.5 


712 lbs. 
1282 •' 
1832 " 
2422 " 



J.XSTAL..LATIOX OF fcTJtfSET CAR MOTORS. 

(General Electric Company.) 

In General. 

In locating the various parts of the equipment and in wiring the car, par- 
ticular attention should be taken to secure the following results : 

1. Maintenance of high insulation. 

2. Exclusion of all foreign material, particularly grease, dirt, and water, 
from the electrical equipment. 

3. The avoiding of fire from arcs, naturally occurring at fuse-box, light- 
ning arrester, etc. 

4. The prevention of mechanical injury to the parts. 

5. The placing of the parts so as to be accessible for operation and inspec- 
tion, and yet out of the way of passengers. 



Preparation of the Car Body. 

The floor should be provided with a trap-door of such size as to allow as 
free access as possible to the motors. Particular attention is called to the 
advisability of having the bar across the car between the trap-doors remov- 
able, in order that the top of either motor can be thrown back. 

The roof should be provided with a trolley board which strengthens it, 
and protects in case the trolley is thrown off ; it also deadens the noise. 
A firm support should be provided for the light clusters. Grooves should 
be cut for the leading wires in the roof moulding, and also in two of the 
corner posts, one for the trolley wire, the other for the ground wire of the 
lighting circuit. 

On a closed car four 2 in. holes should be bored through the car floor under 
the seats, one as near each corner of the car as possible. 

On one side of the car, four § in. holes should be bored in a line, and 4 in. 
apart, to receive the taps from the cable to the leads of motor No. 1. The 
exact location of these holes depends on the type of motor used. The dis- 
tance from the center of the axle to the center of this group of holes should 
be about two and one-half feet for GE motors. On the same side of the car, 
and in the same line, four other f in. holes should be bored 4 in. apart, to 
receive the taps from the cable to the resistance boxes. On the other side 
of the car three f in. holes in a line and 4 inches apart, should be bored 
to receive the taps from the cable to the leads of m otor No. 2, and on 
same side of car and in the same line five other | in. holes 4 inches apart 
should be bored to receive the taps for the trolley, resistance, and shunt for 
Motor No. 2. , ^ ' . t . . , . „ 

Reference should be made to diagram m order that each set of holes shall 
be on the proper side of the car, and at such a distance from side-sills as to 
be- Out of the way of wheel throw. 



INSTALLATION OF STREET CAR MOTORS. 475 



Measuring about 38 inches from the brake-staff and a suitable distance 
inside of the dash rail, an oval hole 5 in. x 2| in. should be cut in each plat- 
form to receive the cables. 

On an open car no holes need be bored for the floor wiring except those 
through the platform. 

Installing- Controllers. 

In the standard car equipment one controller is placed on each platform 
on the side opposite the brake handle, in such a position that the controller 
spindle and the brake-staff shall not be less than 36 inches, nor more than 
40,jnches apart. The exact position depends somewhat on the location of 
the sills sustaining the platform. The feet of the controller are designed to 
allow a slight rocking with the spring of the dasher. Two one-half inch 
bolts secure the feet to the platform. An adjustable angle iron is furnished 
to be used in securing the controller to the dash-rail. A wire guard is also 
furnished, to be secured to tbe platform in such a position that the cables 
pass through it into the controller. A rubber gasket is furnished with each 
controller, to be placed between the wire guard and the platform, to exclude 
water. For dimensions of controller, see Figs. 40 and 41. 

Wiring-. 

This work can be conveniently divided into two parts ; namely, roof 
wiring- and floor wiring. 

Roof wiring includes the running of the main circuit wire from the 
trolley through both main motor switches down the corner posts of the car 
to a suitable location for connecting to the lightning arrester and fuse box ; 
also wiring the lamp circuit complete, leaving an end to be attached to the 
ground. Whenever wires lie on the top of the roof, they need not be 
covered with canvas or moulding, except to exclude water where they 
pass through the roof. In such cases a strip of canvas the width of the 
moulding, painted with white lead, should be laid under the wire, and over 
this and the wire should be placed a piece of moulding extending far enough 
in either direction to exclude water. The moulding should be firmly 
screwed down and well painted. 

The above wiring should be done if possible while the cars are being 
built. 

JFloor wiring may be done after the car is completed without injuring 
the finish. 

Ulade up cables give far better protection to the wiring, and are 
easier to install than separate wires, and should be used in the floor wiring 
if possible. The simplest way of installing them on box cars seems to be as 
follows : 

After the car bodies are prepared according to the above instructions, the 
cables (one on each side of the car) should be run through holes in the plat- 
form, and the connections made to the motors and controllers. 

After making connection to the controllers, all slack should be pulled up 
inside of the car under the seats, and held in place, preferably against the 
side of the car, by canvas or leather straps. Motor taps should project 
through the sills for attachment to the flexible motor leads just far enough 
to permit easy connection, leaving as little chance as possible for vibration. 
No rubber tubing will be required on taps, as they all have a weather-proof, 
triple-braided cotton covering outside of the rubber insulation to prevent 
abrasion. All joints should be thoroughly soldered and well taped. The 
portions of the cables passing under the platforms should be supported by 
leather straps screwed to the floors or sills. Cables should never be bent 
at a sharp angle. The ground wire should run under the car floor rather 
than under the seats. 

On open cars all wires and cables must be run under the car, and should 
be well secured to the floor with cleats or straps. 

A good joint can be made by separating the strands of the tap-wire, and 



476 ELECTRIC STREET RAILWAYS. 



wrapping the two parts in opposite directions around the main wire. Both 
Okonite and rubber tape are furnished. It is desirable that Okonite should 
be used first and rubber tape put over it, as the latter will not loosen and 
unwrap as Okonite will. All openings in the hose sbould be sewed up as 
tightly as possible around the wires. 

Separate wires can be installed if necessary, observing the following 
directions : 

The floor wires on box cars should be placed under the seats as much as 
possible. In the few places where it is necessary for wires to cross, wood 
should intervene in preference to a piece of rubber tubing or loop in the 
air. This rubber tubing is not necessary where wire is cleated under the 
floor (as on open cars), if it does not pass over iron work, or is not ex- 
posed to mud and water. Where so exposed, it should be covered wi*h 
moulding, but where moulding is used it should be carefully painted inside 
and out with good insulating compound to exclude water. The wire passing 
to the fuse box should be looped downward to prevent water running along 
the wire and into the box. Care should be taken to avoid metal work about 
the car in running the wires, and that nails or screws are not driven into 
the insulation. 

In general it is not desirable to use metallic staples and cleats for car- 
wiring, except about the roof, or inside the car. Where wires are subject 
to vibration, as between the car bodies and motors, flexible cable must al- 
ways be used. A certain amount of slack should be left in the leads from 
the motor to the car body, depending on their length. On cars with swivel- 
ing trucks a greater amount of slack is necessary. As sjack gives greater 
opportunity for abrasion, care should be taken to leave only what is abso- 
lutely necessary. 

Operation and Care of Controller. 

When starting, regulate the movement of the handle from point to point 
so as to secure a smooth acceleration of the car. 

I>o not rnn between points. 

The resistance points 1st, 2d, 3d, 6th, and 7th, are intended only for the 
purpose of giving a smooth acceleration, and should not be used contin 
uously. 

For continuous running, use the 4th, 5th, 8th, and 9th points, which are 
shown by the longest bars on the dial. 

When using the motor cut-out switches be sure that they are thrown up 
as far up as they will go. 

In case the trolley is off and the hand-brakes do not hold the car, an 
emergency stop may be accomplished by reversing the motors, and turning 
the power-handle to the full speed, or next to full speed point. 

To examine the controller, which should be done regularly, open the 
cover, remove the bolt with wrench attached, and swing back the pole-piece 
of the magnet. 

The contact surfaces and fingers should be kept smooth, and occasionally 
treated with a small amount of vaseline to prevent cutting. 

All bearings should be regularly oiled. 

A repellent compound, paraffme, rosin, and vaseline, equal parts by 
weight, placed in the water-caps of the power and reversing shaft, is an 
efficient protection against water. 

Dirt must not be allowed to collect inside of the controller. 



Diag-rants of Car Wiring-. 

In general car wiring is carried out in about the same manner for all 
styles and sizes of car, more particular description being given above. Wir- 
ing differs mainly in details, governed by the number, style and horsepower 
of motors used. 



INSTALLATION OF STREET CAR MOTORS. 



477 



Diagrams of standard wiring for two motors per car and for four motors 
per car follow, in Figs. 31, 32, 33, 34. They are all from the G. E. Co. lists, as 
controllers made by that Company are almost universally used, although 
many of older design by other companies are still in the held. 







478 



ELECTRIC STREET RAILWAYS. 




INSTALLATION OF STREET CAR MOTORS. 



479 




o s 

2^ 



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org 



480 



ELECTRIC STREET RAILWAYS. 




Equipment lasts. 



The following is a list of material required for the electrical equipment 
of one car fitted with two motors : 



CONTROLLERS. 481 



QUANTITY. 

1 Trolley pole. 

1 Trolley base. 

2 Motor circuit switches. 
1 Lightning arrester. 

1 150 ampere magnetic cut-out (fuse-box). 

1 Resistance box. 

1 Resistance box. 

1 Core for kicking coil. 

2 Controllers (includes wire guard and gasket, supporting bracket, 

cap screws, and washers for fastening to dasher). 

1 Controlling handle. 

1 Reversing handle. 

One of each of these handles is always shipped with each pair of 
controllers unless specified to the contrary. 

75 ft No. 6 B. & S. strand wire (7-.061 in.) for roof-wiring. 

20 100 or 150 ampere fuses. 

10 Two-way connectors, \ in. hole, No. 6. 

30 Brass corner cleats, T 7 B in. slot. 

25 Brass flat cleats, /g in. slot. 

110 i in. No. 4 R. H. brass wood screws for brass cleats. 

25 Wood cleats, | in. slot. 

25 Wood cleats, f in. slot. 

100 1J in. No. 8 R. H. blued wood screws for wood cleats. 

1 lb. Solder. 

1 lb. | in. Okonite tape. 

1 lb. 1 in. adhesive tape. 

Material for set of cables as follows : 

480 ft. No. 6 B. & S strand wire (7-.064 in.), single braid. 

100 ft. No. 6 B. & S. strand wire (7-.064 in.), triple braid for taps. 

41 Brass marking-tags. 

64 ft. 1£ in. cotton hose. 

1| lbs. Rubber tape. 

4 lbs. Paragon tape. 

1£ lbs. Solder. 

This material can be procured made into a (i set of cables " with- 
out extra cost. 

1 Car-lighting equipment. 



COIIROIIERS. 

Under this heading are included all that type of appliance used for start- 
ing and stopping the motors and controlling the speed of the same. As 
almost all the old forms of rheostat with different steps have been aban- 
doned for the so-called series-parallel controller, it is not necessary to de- 
scribe any other here, nor will any detailed description of those now in use 
be attempted. 

Two distinct forms are now mostly in use ; one, the magnetic blow-out type, 
made by the General Electric Company and used by the Westinghouse Elec- 
tric and Manufacturing Company ; the other the so-called solenoid blow-out 
type, made by the Walker Company, of Cleveland, Ohio. 

The principle of the magnetic blow-out type was first developed by Prof. 
Elihu Thomson, i. e., that an electric arc in a strong magnetic field is 
blown out of line and extinguished or cut in two. This fact is taken ad- 
vantage of in the controller of the General Electric Company by using a 
strong electro-magnet to extinguish the arcs formed at the contact-points, 
when the circuits are broken. The construction is shown m the cut of 
Series-parallel controller, form K2, following. ..,,*». 

The theory of the solenoid blow-out of the Walker Company is said to be 
that the arc is lifted out of place, and eases down the current, thus cutting 
it off easily, and without bad inductive effects. The following cut shows 



482 



ELECTRIC STREET RAILWAYS. 



the connection aud supposed action, and further along will be found cuts 
showing the assembled controller, the same developed, and a diagram 
showing general dimensions. 




Fig. 35. Enlarged diagram showing theory of 
Solenoid Blow-out Controller of Walker 
Company. 

Controllers are now made in so many forms and varieties that it is im- 
possible to give more than a few of the combinations which are practi- 
cally the same everywhere in the United States. 




Fig. 36. Series-Parallel Controller, Form K2. 
General Electrie Company. 
Used also by the Westinghouse Electric and Manufacturing Company, and 
others. 



CONTROLLERS. 



483 



The General Electric Company manufactures controllers for all condi- 
tions of electric railway service. They are divided for convenience in desig- 
nation into four general classes, each designated by an arbitrary letter. 

Type K. Controllers are of the series parallel type, and include the 
feature of shunting or short circuiting one of the motors when changing 
from series to parallel connection. 

Type I* Controllers are also of the series-parallel type, but com- 
pletely open the power circuit when changing from series to parallel. 

Type B Controllers may be either the series-parallel or rheostatic 
type, but always include the necessary contacts and connections for operat- 
ing electric brakes. 

Type K Controllers are of the rheostatic type and are designed to 
control one or more motors by means of resistance only. 




Fig. 37. " R " Type of Rheostatic Controller. 



Rheostatic Controllers. 



» 11 Controller. 



Designed for one 50 h.p. motor. 

Can be wired for use with motors using either shunted or full field. 

Total number of notches, six. 

(The Rll controller has been known as the KR controller.) 

II 13 Controller. 

Designed for two 50 h.p. motors. 

Same as Rll controllers with exception that magnet-coils and contact- 
fingers are of greater capacity, and reversing-switch is arranged 
for two motors. 



484 



ELECTRIC STREET RAILWAYS. 



Series Parallel Controllers. 



Title. 


Capacity. 


Controlling 
Points. 


Remarks. 


K 


Two 35 h.p. 

Motors. 


4 Series. 
3 Parallel. 


For motors using loop or shunted, field. 


K-2 


Two 35 h.p. 
Motors. 


5 Series. 
4 Parallel. 


For motors using loop or shunted field. 


K-4 


Four 30 h.p. 

Motors. 


5 Series. 
4 Parallel. 


For motors using loop or shunted field. 


K-6 


Two 80 h.p. 

Motors or 

Four 40 h.p. 

Motors. 


6 Series. 
5 Parallel. 


Connection board so arranged that con- 
troller may be used for two or four motors 
on grounded or metallic circuit. 


K-7 


Four 30 h.p. 

Motors. 


5 Series. 
4 Parallel. 


Similar to K-12, but arranged for metallic 
circuit system. 


K-8 


Two 50 h.p. 
Motors. 


5 Series. 
4 Parallel. 


Similar to K-ll, but arranged for metallic 
circuit system. 


K-9 


Two 35 h.p. 
Motors. 


5 Series. 
4 Parallel. 


Similar to K-8, but has connecting wires 
and blow-out coil of smaller capacity. 


K-10 


Two 35 h.p. 

Motors. 


5 Series. 
4 Parallel. 




K-ll 


Two 50 h.p. 

Motors. 


5 Series. 
4 Parallel. 


Similar to K-10, but has connecting wires 
and blow-out coil of larger capacity. 


K-12 


Four 30 h.p. 

Motors. 


5 Series. 
4 Parallel. 


The K-12 is a K-ll with reversing switch 
arranged for four motors. 


K-13 


Two 125 
h.p. Motors 


7 Series. 
6 Parallel. 




K-14 


Four 60 h.p. 
Motors. 


7 Series. 
6 Parallel. 




L-2 


Two 175h.p. 

Motors. 


7 Series. 
7 Parallel. 




L-3 


Four 175 
h.p. Motors 


9 Series. 
7 Parallel. 


' 


L-4 


Four 100 
h.p. Motors 


7 Series. 
7 Parallel. 


Similar to the L-2, but with additional re- 
versing switch parts for four motors. 


L-6 


Four 200 
h.p. Motors 


9 Series. 
6 Parallel. 


Special for Central London Locomotives. 
Handle moves in counter-clockwise direc- 
tion for turning on power. 


L-7 


Four 200 
h.p. Motors 


9 Series. 
6 Parallel. 


Differs from the L-6 in the direction of ro- 
tation of the operating handle. 



Electric Brake Controllers. 



Title. 


Capacity. 


Controlling 
Points. 


Remarks. 


BA 


Two 35 h.p. 
Motors. 


5 Series. 

4 Parallel. 

6 Brake. 


Power connections same as K-2. For mo- 
tors using shunted field for running 
points. 


B-3 


Two 35 h.p. 

Motors. 


4 Series. 
4 Parallel. 
6 Brake. 


Has no points for shunting motor fields. 
Superseded for general use by the B-13. 


B-5 


Two 50 h.p. 

Motors. 


4 Series. 
4 Parallel. 
6 Brake. 


Similar to B-3, but has heavier connecting 
wires and blow-out coil. Superseded for 
general use by the B-23. 


B-6 


Four 
30 h.p. 

Motors. 


4 Series. 
4 Parallel. 
6 Brake. 


Similar to B-3, but has reversing switch and 
brake contacts arranged for four motors. 
Superseded for general use by the B-19. 



CONTROLLERS. 



485 



Electric Brake Controllers. — Continued. 



Title. 


Capacity. 


Controlling 
Points. 


Remarks. 


B-7 


Two 100 
h.p. 

Motors. 


6 Series. 

5 Parallel. 

6 Brake. 


Has separate brake handle. 


B-8 


Four 
50 li.p. 

Motors. 


6 Series. 

5 Parallel. 

7 Brake. 


Has separate brake handle. 


B-13 


Two 
40 h.p. 
Motors. 


5 Series. 
4 Parallel. 
7 Brake. 


Supersedes the B-3, from which it differs in 
having contacts for connecting motor 
armature in series with their respective 
brake shoes. 


B-16 


Two 
50 h.p. 

Motors. 


5 Series. 
4 Parallel. 
7 Brake. 


Similar to B-23, but has special connections 
for the surface contact system. 


B-18 


Two 
35 h.p. 
Motors. 


4 Series. 
4 Parallel. 
6 Brake. 


Differs from the B-3 in that it has an extra 
cut-out switch blade, and connection board 
arranged for motors using metallic or 
grounded circuit. 


B-19 


Four 
40 h.p. 

Motors. 


6 Series. 

5 Parallel. 

7 Brake. 


Similar to B-8, having separate handles for 
power and brake. Supersedes B-6. 


B-23 


Two 
50 h.p. 

Motors. 


5 Series. 
4 Parallel. 
7 Brake. 


Supersedes the B-5. Similar to the B-13, 
but has connecting wire and blow-out coil 
of larger capacity. 


B-24 


Two 
40 h.p. 
Motors. 


5 Series. 
4 Parallel. 
7 Brake. 


Similar to B-13, but has cut-out switches 
arranged for metallic circuit systems. 


B-25 


Two 
50 h.p. 
Motors. 


5 Series. 
4 Parallel. 
7 Brake. 


Similar to B-24, but has connecting wire 
and blow-out coil of larger capacity. 


B-29 


Two 
50 h.p. 
Motors. 


5 Series. 
4 Parallel. 
7 Brake. 


Similar to B-23, but has separate brake 
handle. 



Rheostatic Controllers. 



Title. 


Capacity. 


Controlling 
Points. 


Remarks. 


R-ll 


One 50 h.p. 
Motor. 


6 


For motors using either full or shunted 
fields for running points. 


R-12 


Two 50 h.p. 
Motors. 


6 


Motors are connected permanently in par- 
allel. 


R-14 


Two 35 h.p. 

Motors. 


5 


Very short and specially adapted to mining 
locomotives. Motors are connected per- 
manently in parallel. 


R-15 


Two 75 h.p. 
Motors. 


6 


Motors are connected permanently in par- 
allel. 


R-16 


Four 35 h.p. 
Motors. 


6 


Similar to R-15, but has reversing switch 
arranged for four motors. 


R-17 


One 50 h.p. 
Motor. 


6 


Similar to R-ll, but has resistance on the 
trolley side of the motor instead of on the 
ground side. 


R-19 


Two 50 h.p. 

Motors. 


6 


Similar to R-17. Motors are connected 
permanently in parallel. 


R-22 


Two 50 h.p. 
Motors. 


5 


Shape like R-14, others same as R-12. Mo- 
tors are connected permanently in parallel. 



486 



ELECTRIC STREET RAILWAYS. 



MOTOR COMBINATIONS 



CONTROLLER 



RES. MOTOR 1 MOTOR 2 




-HUr ^-o — 'MV J r o — \w-L- 

J= Lp- TOT^| - K> ir W V- 



RES. MOTOR 1 MOTOR 2 




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Fig. 38. 



RES. MOTOR 1 MOTOR 2 

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SERIES L2 CONTROLLER MULTIPLE 



RES. MOTOR 1 MOTOR 2 




CIRCUIT OPEN 
CHANGES TO MULTIPLE 
SEE NEXT COLUMN 

Fig. 39. 




CONTROLLERS. 



487 




nsi^& ° 






Figs. 40 and 41. Diagrams for 
^Dimensions of" 



Dimensions of Controllers. 
Controllers. 



Type K. 




Type 


L. 




M 




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488 



ELECTRIC STREET RAILWAYS. 

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THE SPRAGUE MULTIPLE UNIT SYSTEM. 



489 




f 


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i 


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Rb 


1 




Figs. 42 and 43. Diagrams for Dimensions of Controllers. 



THE §PRA«rE ITMJITI^M UKTIX SYSTEM. 

BY FRANK J. SPRAGUE IN STREET RAILWAY JOURNAL, MAY, 1901. 

This system, briefly defined, is a system of control of railway motor con- 
trollers, whatever their number and wherever situated in a train, through a 
secondary electric circuit common to all the cars from or through which it 
is desired to exercise control. The number and position of equipped or 
unequipped units, and to a certain extent the character of these nnits, i^ 
immaterial, and variation in end relation is likewise a matter of indifference. 

The system covers the entire range of service from a single car operated 
as an independent unit to a train of any length equipped with as ruuch or 
little power as required. 

In General. 

Each motor car is equipped with complete power operated apparatus for 
its motors, and has in addition an independent train line by means of which 
it can be operated from other cars, as well as operate other cars. This train 
line terminates in shrouded couplers under the platform at each end of the 
car. The train lines on different cars, whether equipped with motors or 
not. are joined by detachable reversible jumpers. 

The train line is especially designed to secure reliability. To insure this 
it carries only small currents, and has but four or five controlling wires 
There is no ground wire carried through the train line. Provision is made 
for a relay line to be carried in the common cable for the operation of the 
air compressors. The wires are each thoroughly insulated and the cable is 
protected from mechanical injury. The train line is completely isolated 
from the local circuits on each car. The operating relays, energized from 
the train line on each car, are each separately protected so that their fail- 
ure cannot interfere with the operation of unaffected cars The operation 
is in no way affected by changes in the sequence of cars 

The train line can be readily cut off from the local circuits on any car. 

The local pilot motor circuit and main motor circuits are independent of 
the train line, so that no derangement of main circuits or apparatus can be 
communicated to it. 

Each pair of motors is controlled by the joint operation of a speed con- 
troller and reverser. The main circuit is opened independently by each. 
Any derangement of either renders that car inoperative. This is secured by 
interconnection of operating circuits, so that current cannot be continued 
through motors. 

Each car automatically governs the current input in the car, and insures 
the most efficient acceleration and operation independent of the motorman. 
Means are also provided to restrain the current input at will by manipula- 
tion of the master switch. 

Protection is automatically provided against any improper operation at 
the master switch, or misplacement or failure of any part of the system. 
In any case, the indicated result will follow a movement of the master 
switch, or the main circuit will be opened and the apparatus rendered 
inoperative. 



490 



ELECTRIC STREET RAILWAYS. 



Circuits. 

The system is illustrated by an elemental diagram, Fig. 44, two typical 
circuit diagrams, Figs. 45 and 47, with and without the coast relay, showing 

also the development of the appara- 
tus, and two corresponding schematic 
diagrams, Figs. 46 and 48, showing con- 
trolling circuits only for single cars. 
Reference to the diagrams shows that 
on a fully equipped car there are four 
distinct circuits, which are shown by 
distinguishing lines. These are : 

Cai'*niotor Circuit. — This in- 
cludes the main motors, the contacts 
with the supply circuit, and the re- 
verser, rheostat and motor grouping 
contacts which are in the circuit of 
the main motors. 

JLocal Operative or Control- 
ling- Circuit. — This includes the 
relay or magnet coils, pilot motors, or 
whatever directly moves or controls 
the main motor controllers, or actu- 
ates main controlling contacts when 
the system is, as here shown, entirely 
electric, or controls the pilot mechan- 
ism if some other power than electri- 
city is used to move the main con- 
trollers. 

Platform-switch Line. — This 
on a single car becomes a part of the 
local operative circuit, and on a train 
energizes all the local operative or 
controlling circuits through the inter- 
mediary of the particular platform- 
switch in use, and the electrical train 
or governing lines on it and the other 
cars. 

Train or Governing- line. — 
This is the continuing cable running 
from one car to another, which at one 
or more points is connected, on the 
one hand to the platform-switch line, 
and on the other to the local operative 
circuits. It is made up of the per- 
manently placed train line on the sev- 
eral cars and the couplers or jumpers 
connecting them together. It may evi- 
dently be common to cars which are 
equipped with and to cars which are 
not equipped with motors. It is the 
independent means of transmitting an 
initial and governing impulse from any 
one of a number of points. 

Operation. 

The specific operation of the appa- 
ratus controlled by these circuits is as 
follows : 

On each of the fully equipped cars 
there are two main motors. Each mo- 
tor has a single unchangeable set of 
field coils and an armature. The mo- 
tor connections and the current flow- 
ing therein are determined by three 
principal switches. There is a r'everser 
for changing the armature connections 




THE SPRAGUE MULTIPLE UJSTIT SYSTEM. 



491 




492 



ELECTRIC STREET RAILWAYS. 



of the two motors, a rheostat for varying the resistance in the circuit 
with them, and a motor switch for effecting series or parallel relation. 
These three pieces of apparatus can be physically separate, or any two or 
all three can be combined in one structure/ As here shown, the two switches 
which determine speed form one structure, termed- the main controller, and 
the reverser the other. 

These main switches are primarily controlled from a master switch on 
each platform of any equipped car, through a train line and suitable relays 
and a pilot motor. This master switch is a multiple circuit maker, a means 
for closing the line supply to one or more independent train wires, each of 
which operates a relay. This switch has neither mechanical nor electrical 
connection of any kind with the motor circuits, nor, although it has certain 
corresponding position, is its movement necessarily coincident with, nor 
proportional to, the movement of any of the main switches. 

In ordinary operation, the two motors are first put in series with each 
other with suitable resistance, which is cut out until the full half potential 




]Fuse 

I XShoe 

I Fuse n „ e 

U Cut-off^ Train Line 

S {ohms si. 







_]i j ! ! Coupler 



FlG. 46. Schematic Diagram of Control Circuits Only, Sprague System. 



is supplied to each motor, which is the half-speed combination. In going 
thence to full speed, the main circuits are first opened instantly at the main 
controller, or, if desired, progressively through resistances and independent 
main contacts, or they can be opened at the reverser. 

The motors are then thrown into multiple relation with a resistance in 
circuit of about one-quarter that used in the first series position, which is 
progressively cut out until the motors have full potential, and run at their 
full capacity and speed. The quartering of the resistances on the first 
position is effected by using independent resistances in each motor, throw- 
ing them in series and parallel relation the same as the motors, and using 
the same progressive steps. 

In any position of the controller the current can be cut off either instantly 
by the reversers, which have independent main-line contacts, or progres- 
sively at the main controller. 

The reverser contacts for the armatures of the two motors, as well as two 
extra " line" contacts, are for convenience mounted on a common spindle. 
The cylinder of the reverser is normally retracted to a middle or open 



THE SPRAGUE MULTIPLE UNIT SYSTEM. 



493 



circuit position, and there are two solenoids, one for pulling the cylinder 
one way for ahead movement of the train, and the other for pulling it the 
opposite way for backward movement. 

Provision is made for dead-beat movement, and also for inter-connection 
of controlling circuits by contacts on the same cylinder as the main 
contacts. 

The circuit for the reverser passes through the automatic stop coil, and 
is completed througb a by-pass on the controller in the first contact posi- 
tion, or through a contact made by the automatic, so that once opened it 
cannot be operated unless the controller is in a safe position for the 
motors. 

The cylinder of the main controller is driven with an intermittent motion 
by a pilot motor through a powerful locked spring, so that the armature of 
the pilot motor and the spindle of the cylinder do not move either in 
synchronism or to an exactly like extent. This is necessary to insure free- 
dom from hot contacts and dragging of arcs. 



Main Control >e 



JC Switch 

3=) ( o jAnnatrira 




f?lT fSwitebl ° fl !! 

! mg— t- •, i — f !• 



aiaateii ! Switch 
flG Fuses 



"1f 

i s j '.'< 

Throttle c=i ' — ' • L« 

Clioa'ott Reverser 



CJOIIS j 

ifiSSXiSJ 




Fro. 47. Schematic Diagram, Control Circuits Only, Without Coast Relay. 



The pilot motor is governed by either four or five relays called, respec- 
tively, the "coast," "series," and "multiple" relays, the "automatic 
stop" and the "throttle." Since the "automatic stop" also has coast 
relay contacts, the separate coast relay may be discarded. 

There are three allowable running positions for a pair of motors, — the 
coast or open circuit position, the series position, when the two motors are 
in series without any resistance in circuit, and the multiple position, when 
the two motors are independently across the line without any resistance. 
In addition, the motors can be run temporarily with more or less of the 
resistance in circuit for the purpose of switching. On heavy railroad work, 
such as on elevated and suburban roads, minor variation of running speed 
in either the series or the multiple relation of tbe motors by the use of 
resistances is rarely practiced, and is never necessary save in starting. The 



494 



ELECTRIC STREET RAILWAYS. 




apparatus is especially constructed to discourage any such variation of 
running speed. 

The circuit which operates the pilot motor on each car is a purely local 
circuit, coming from the car shoes and returning to the track, just as the 
main circuit of the motor does. It is not connected to the train line or the 
master switches in any way. Its path is through the field magnets, break 



THE SPRAGUE MULTIPLE UNIT SYSTEM. 



495 







of current, it can become an automatic 
of acceleration. It does not prevent 



and armature of tlie pilot 
motor, through the contacts 
of the coast, series, or 
multiple relays, and also 
through the contacts of the 
throttle and automatic stop. 
If either the throttle or the 
automatic stop are in an 
open circuit position it is 
impossible for the pilot mo- 
tor to move in one direction, 
and it is hence impossible 
for the controller to be ad- 
vanced, althotigh if in an 
advanced position it can be 
moved backward. Tbe cir- 
cuits through the relay con- 
tacts and the pilot motor 
also pass through limit 
switches on the controller 
cylinder. If this control 
cylinder is in " off " posi- 
tion, and the throttle and 
automatic stop are in proper 
positions, closure of the 
coasting relay would not 
cause any movement what- 
ever, but closure of the 
+5 series relay will allow the 
pilot, if otherwise uninter- 
rupted, to move the con- 
troller to the series position, 
Ss where it will automatically 
a stop. In the same way clos- 
£ ure of the multiple relay 
Ph will move the controller 
*2 either from the coast posi- 
O tion or from the series posi- 
tion to the full multiple 
2> position, where it will be au- 
. tomatically stopped. Open- 
g ing the throttle, however, 
fe will either arrest or retard 
the rotation of the pilot 
motor and the progression 
of the controller, and drop- 
ping of the automatic stop 
or opening of the reverser, 
which is also provided with 
a coasting contact, will at 
once return the controller 
to an open circuit or any 
other determined position, 
regardless of the motorman. 
The throttle is operated 
automatically by the cur- 
rent in one of the motors, 
and serves a double pur- 
pose. 

It retards or stops the 
forward movement of the 
main controller at any de- 
sired current increment, 
and, since it responds to 
a determinate rise and fall 
switch for providing a definite rate 
any desired slower rate of accel- 



496 ELECTRIC STREET RAILWAYS. 



eration, or in any way remove from the motorman the positive operation 
of the main controller at will within the limits of safe and desirable current 
inputs. Further reference to its action will be made. 

It will be seen, therefore, that the physical operation of the controller is 
intermittent in character, and certain automatic controlling devices are 
provided which modify its operation. 

A single car will first be considered. The coast, series and multiple relays 
are energized by platform-switch circuits, which terminate in a master 
switch or controller at the platform, at which a connection to the supply 
circuit is also made. To this same master switch are brought also the 
terminal wires of the solenoids operating the reverser. This master switch 
is the apparatus manipulated by the motorman, and except as he is limited 
by the automatic features, or hindered by circumstances which he cannot, 
and is not intended to, control, all operation either of the particular car or 
the train is initiated at this point. 

The master switch consists of a cylinder with suitable contacts operated 
by a handle interlocked with the top of the switch. Against the cylinder 
rest a set of fingers, and between each pair of the fingers is an insulating 
shield or separator, the separators being mounted on a common spindle. 
The speed and direction of car movement are initiated at this master switch 
by the movement of a single handle. The switch has (1) the off or normal 
position, to which the handle is spring retracted in case the operator lets 
go of it, (2) for ahead movement, three running positions, coast, series and 
multiple or full speed, with no contacts between, and (3) for the back move- 
ment, two running positions, coast and series or half-speed position. The 
car can be stopped and reversed by a single throw of the handle of the 
operator's or master switch from one side of the open position to the other. 

It will be noted that there is no physical, nor even any electrical, con- 
nection whatever between the master switch and the main controller. There 
is simply an electrical connection with the three relays spoken of, and with 
the solenoids of the reverser which form a part of the main control system. 
Movement, therefore, of this handle only indirectly affects operation of the 
main parts of the apparatus under certain conditions and when certain 
circuits permit such operation. 

The ordinary operation is that when a motorman wishes to go ahead at 
half-speed he moves the master controller to the series position. The 
reverser is instantly set for movement ahead, the series relay is closed, the 
pilot motor starts up, the driving spring is put under tension, and the con- 
troller spindle moves forward intermittently until the pilot limits stop it at 
the half-speed position. If during this operation the throttle should lift, 
this advance of the controller cylinder will be retarded or stopped. If the 
automatic stop should drop, the advance not only will be stopped, but the 
controller will at once run backward to an open circuit or other determined 
position without regard to the set of the series relay, or what is the wish of 
the man at the master switch. 

Being at the series position, if the motorman wishes to go at full speed, 
the handle of the master switch is moved to that position, when similar 
operations take place at the relays and pilot motor. 

Or the operator may move his switch handle at once from the open circuit 
to the multiple position without any regard to the series position, and the 
main controller, controlled by the throttle, will advance to full-speed 
position. Of course the advance of the main controller may be made at 
will, step by step, by touch-and-go contact at the master switch, and its 
advance can be arrested instantly. If desirable, when a coast relay is used 
its connection can be changed so as to, at will, throw the throttle out of 
action, althoiigh this is not desirable. 

By minor changes in the controlled circuits they can be arranged so that 
the operator can operate entirely with the motors in series or entirely in 
multiple, or either at will. This is because the controller has two circuit 
positions, one at the beginning of the series combination and one at the 
beginning of the multiple combination. It is what is known as an open- 
circuit controller, and provision is made for not only opening circuit in two 
placed on its cylinder, but also independently on the reverser. 

Comparison of the movements of the master switch and the main con- 
troller illustrate very clearly the inter-connection of controlling circuits 
and their utility, and how they are intended to provide for every emergency. 
The master switch has two running advance positions and one running 



THE SPRAGUE MULTIPLE UNIT SYSTEM. 497 



back position, and movement of its handle between those two points in no 
way affects the main controller ; the latter has several positions where it 
can rest with identically the same position of the master switch handle pro- 
vided its motion is arrested before it has reached one of its limits ; under 
certain conditions the controller will not make any motion whatever in 
response to a master switch ; under certain other conditions, it will make 
a partial response, then automatically stop, and without any change of 
movement of the master switch go ahead again and automatically stop ; 
the controller, under other circumstances, will respond to the master 
switch, then stop, and immediately, or after an interval, go back to an open 
circuit or any other predetermined position ; under changed circumstances 
it will advance intermittently to, or toward, some determined position 
indicated by the master switch, then stop, go backward to some other 
position, and then go forward again ; or in passing from a coast or open 
circuit to a multiple position, the controller may or may not respond to 
closure of the series contact. If the motorman wishes to reverse the car 
while going ahead, with the motors in either the series or the multiple 
position, the master switch can be instantly thrown to the reverse series 
position, and the controller while immediately responding, will not in like 
degree, for as the master switch passes the off position the reversers will 
open, the main circuit of the motors will be instantly interrupted, the 
automatic stop on each car will run the controller back to some other 
determined position, the reversers will then close, and the series refciy, 
which, although set by the master switch, has, up to that moment, been 
entirely inoperative, will now allow the pilot motor, controlled by the 
throttle, to intermittently move the controller to the reverse half-speed 
position. 

If the by-pass on the controller is of proper length the reverser will close 
circuit as soon as the controller has returned to, say, the first resistance 
position, and it will remain there until the current has dropped below the 
safe amount. 

In short, to all apparent intents and purposes, the controller seems pos- 
sessed of an independent intelligence, because the relay system and the 
inter-connection of circuits is such that all local emergencies are provided 
for, as they must be, without regard to the wishes, intents or carelessness 
of an operator. 

To connect two or more cars together, and to provide for the initiation of 
the operation of the controllers on such other cars as may be fully equipped 
from one or more of the master switches, an independent train line is 
provided, which is the extension of the platform-switch circuit from car to 
car, through fixed train cables on each car terminating in couplers at the 
ends of the cars, and flexible and reversible train cables, or jumpers, ter- 
minating in couplers with complementary contacts joining the several train 
cables together at the ends of the cars. These train lines and jumpers are 
so connected to the coupling heads that the controlling circuits are auto- 
matically paired to insure proper operation of the various main controllers 
from any master switch without regard to what are the abutting ends of 
the cars, or what is their number or sequence, or how the jumpers are 
reversed, or whether, as in practice, they are coupled indifferently on one 
side or other on the cars. 

All roads, of course, do not change their sequence in the make-up of 
trains, but on many the cars are reversed, as in the operation of open-end 
relays, cross-overs and loops and yards. It follows that not only must 
there be a pairing of the sets of 'speed and direction circuits, but the 
individual speed circuits must always be paired alike, while the individual 
direction circuits must at times be changed in connection. These conditions 
have developed an invariable law of connections for the master and train 
line and jumper connections to get proper co-operation of the motor and 
like relative directional and hand movements under all circumstances. 

The platform-switch circuits, the local operating or relay circuits, and the 
train-line circuits are joined together by switches which permit such inde- 
pendent connection on each car that controllers on any car can be operated 
from the master switch on its car, no matter how a train is made up, with- 
out the controllers on other cars being affected, or the controllers on as 
many cars as are desired can be operated from the master switch on another 
car without the controller on that car being operated, as well as the normal 
operation of all controllers from any master switch. 



498 ELECTRIC STREET RAILWAYS. 



Normally, movement then of any master switch (the others for the time 
being inoperative and held at open circuit) closes like relays on each car, 
and starts the sequence of operations which I have indicated above for a 
single car. 

Here again, however, the automatic variation of movement already 
described in regard to a particular controller, takes place independently on 
each car, and different kinds and degrees of movements of the controllers 
on different cars could take place simultaneously if necessary. 

Not only that, but to provide for difference of wheel diameters, difference 
of tractive co-efficients on different wheels, and to provide also against any 
irregular condition on any car, similar movements may be differently timed, 
and different controllers may take different relative positions when meas- 
ured by time, each accommodating itself to the limiting current input 
determined for itself. 

It therefore becomes possible, by this combination of positive and semi- 
automatic control, to combine cars having controllers of different sizes, 
motors of different capacities, resistances of different gradations, gears of 
different ratios, and wheels of different diameters, and to successfully 
operate them all from one or more controlling points. The total weight of 
equipment per car other than the motors, platform switches, and train 
cables, is 1,972 pounds. At the time of going to press, both the Westinghouse 
Electric & Manufacturing Company and the General Electric Company had 
de\»eloped modified forms of multiple control, but few cars equipped with 
them had been put in actual commercial use. 

APPROXIMATE MAXES OX BEPRECIATIOar OI¥ 

EIECIRIC STREEX RAIIWAY§. 
(Dawson.) 

Buildings 1 to 2 % Feeder cables , . . . 3 to 5 % 

Turbines 7 " 9 " Lighting and current 

Boilers 8 " 10 " meters 8 " 10" 

Dynamos and Engines, Cars 4 " 6" 

belted plants . . . 5 " 10 " Repair shop and test- 
Belts 25 " 30 " room fittings . . . 12 " 15" 

Large, slow-speed steam Motors 5 " 8" 

engines 4 " 6 " Rotary transformers . . 8 "10" 

Large, slow-speed direct- Boilers and engines . . 6 "10" 

driven plants . . . 4 " 8 " Spare parts l£ " 2" 

Stationary transformers, 5 " 6 " Track work 7 " 13" 

Storage batteries in cen- Bonding 6 " 10" 

tral stations . ... 9 " 11 " On remaining capital ex- 
Trolley line 4 " 8 " penditure 4 " 6" 

If interest rate is 5 per cent, and plant has to be renewed at the end of 20 
years, 3 per cent of original outlay must be reserved annually to provide for 
renewal. 

DEPRECIATION OE STREET RAILWAY MA- 
CHINERY AIR EaUIPMENT. 

Rates Stated l»y Chicag-o City Railway in "• Street Railway 
Journal," Dec, l»OS. 

Power-Station. Engines, 8 per cent ; Boilers, 8 per cent ; Gene- 

rators, 3 per cent ; Buildings, 5 per cent. 

Cal>le I?Iachinery. Cable machinery, 10 per cent ; Cables, 175 per cent. 

Koa<ll»ed. Rails, 5.5 per cent ; Ties, 7 per cent. 

Paving-. Granite, 5 per cent ; Cedar blocks, 16 per cent ; 

Brick, 7 per cent ; Asphalt, 7 per cent ; Macadam, 
6 per cent. 

Cars. Car bodies. 7 per cent ; Trucks, 8 per cent. 

Rolling- Stock. Armatures, 33 per cent; Fields, 12 per cent; Gear 

cases, 20 per cent ; Controllers, 4 per cent ; Com- 
mutators, 33 per cent. 
Wiring and other electrical equipment, 8 percent. 

ILine Equipment. Iron poles, 4 per cent ; Wood poles, 8 per cent ; In- 
sulation, 12 per cent ; Trolley-wire, 5 per cent ; 
Trolley insulation, 7 per cent ; Bonding, 8 per 
cent. 
All based upon renewals and per cent of wear. 



TRACK RETURN CIRCUIT. 



499 



CAR HEATOCf BY ELECTRICITY. 

Test on Atlantic Avenue Railway, Brooklyn. 



Cars. 


Temperature F. 


Watts 


Doors. 


Windows. 


Contents, 
Cu. ft. 


Outside. 


Average 
in car. 


Consumed. 


2 
2 
2 
2 
4 
4 


12 
12 
12 
12 
16 
16 


850J 
850* 
808i 
913* 
1012 
1012 


28 
7 

28 

35 
7 

28 


55 
39 
49 
52 
46 
54 


2295 
2325 
2180 
2745 
3038 
3160 



TRACE RETURN CIRCUIT. 

It goes without saying that the return circuit, however made, whether 
through track alone or in connection with return feeders, should be the best 
possible under the circumstances. Few of the older roads still retain the 
bonds and returns formerly considered ample and good enough. 

Electrolysis and loss of power have compelled many companies to replace 
bonds and return circuits by much better types. The British Board of Trade 
paid especial attention to the return circuit in the rules gotten out by them 
(see page 504), and many American railroads would have been much 
in pocket to-day if sucb rules had been promulgated in the United States at 
the beginning of the trolley development. 

With few exceptions the practice of engineers has been to connect the 
rail joints by bonds, both rails of a track together at intervals, and both 
tracks of a double-track road together. To this has sometimes been added 
track return wires laid between the rails, and in other cases return feeders 
from sections of track have been run to the power-house on pole lines. 

The writer favors the full connection return with frequent insulated 
overhead return feeders where there may be danger from electrolysis of 
water and gas pipes ; in fact, ample return circuit has been proved time and 
again to be the only preventive of that trouble. 

Careful and continuous attention should be given to bonds from the 
moment cars are started on a line. 

Dr. Bell gives the following ratios of track return circuit to overhead sys- 
tem as being average conditions. 



Let 
Then 





R, =z res 




R = res 


R,= 


.1 to .'2R. 


R,= 


.2 to .3R. 


R,= 


.4 to .6R. 


R f = 


.2 to .3/?. 


R,= 


.3 to .7R. 



esistance of track return circuit, and 
esistance of overhead system ; 

Exceedingly good track and very light load. 
Good track and moderate load. 
Fair track, moderate load. 
Exceptional track and large system. 
Good track, large system. 
Rj = .7 to 1.0R. Poor track, large system. 

In exceptional cases track resistance may exceed that of overhead system. 
It is sometimes assumed that R y = .25R, but this is rather better than 
usual. 
Under ordinary conditions R, = .±R is nearer correct. 

11 J Dist 
If formula for copper circuit = cm. = = then for R, = 4/?, the 

±L 

constant 11 should be increased to between 14 and 15 in order that copper 
drop may bear correct proportion to that of the ground return. 

Some forms of rail bond are shown on the following pages ; most of these 
are applied to the rail by pressure or hammer riveting, but some of our bet- 
ter road managements are now soldering all bonds by strong heat. 



500 



ELECTRIC STREET RAILWAYS. 






A few roads still use wire secured hi the web of the rail by steel channel 
pins, which is about the easiest and cheapest, as well as the least efficient 
form of bonding. 

As copper bonds have a high value as junk, many of the long type are now 
stolen from suburban railways, and the tendency is strongly in favor of tbe 
concealed or protected bond which is so designed as to go in the space back 
of the fish plate against the web. For a time these protected bonds were 
made very short, and no very great attention paid to their flexibility, but 
experience has proved that no bond of less than eight or nine inches will 
last well, no matter how flexible. Solid conductor bonds are only available 
for the outside of fish plates, and not less than two feet in length. In apply- 
ing the copper bonds to the rails, it is necessary to apply them immediately 
after drilling the web, unless holes are made at the rail mill and carefully 
oiled, in which case the oil should be very carefully removed before apply- 
ing the bond. 

Bonds are best applied by a medium using heavy pressure, either by 
screw or hydraulic pressure, rather than by hammer riveting. 

On many of the systems, in large cities, rails are made practically contin- 
uous now by use of electrically welded joints or cast weld joints. 

In the electrically welded system a piece of iron about nine inches long, 
two inches wide, and an inch thick is welded across the joint on each side of 
the rail web by means of a heavy current of electricity applied by special 
machinery, taking its power from the trolley system. After the straps are 
welded in position, the tops of the rail ends are carefully ground to an e\en 
surface. Contrary to the ordinary ideas of the results of expansion and 
contraction, but little trouble is experienced by broken joints or bent rails, 
and in most places, where the method is in use, it has been quite successful. 
The system is controlled by the Johnson Steel Co. of Cleveland, Ohio. 

The cast weld joint is simply a bunch of cast iron cast about the joint 
after it has been cleaned and prepared by placing a mold under it. Tbe 
Falk Company of Milwaukee makes a specialty of bonding street railway 
systems in this manner, and the results seem to have been good. 

Several forms of plastic bond have been devised and used to some exent. 
They all consist of some form of plastic metal held in position between the 
fish plate and the rail web, the surfaces of both being treated chemically 
or otherwise, so as to remove scale and oxide so that the plastic material 
may be applied directly against the web. 

Solid Bonds. —This type is simply a heavy copper bar, say No. 0000 
B. & S. gauge, with the ends compressed to form a collar, and bent to fit 
the holes in the rails, and their hammer riveted to place. 

A good example is that made by Messrs. Benedict and Burnham, and 
shown in Figs. 50, 51, 52, and 57. 

Benedict and Burnham Solid One-Piece Rail-Bond. 




Fig 50. Short thick Bond applied to " Tram " of Girder 
Rail, allowing constant inspection. 



\ " 


fej 


L= 


o o o o o o 








T- yf 




1 








k — 8>' 3 — ^J 


1 

— 1 



Ftg. 51. Short thick Bond applied to Base of either 
Girder or T Rail. 



TRACK RETURN CIRCUIT. 



501 



j jJ o o o o o o I 



o 



Fig. 52. Solid long Bond clearing the Fish-plate in either 
Girder or T Rail. 



.Protected Bonds. — Good examples of these are exhibited in Figs. 
53, 54, 55, 56, which show the type of protected bond sold by the Mayer 
& Ehglund Co. of Philadelphia. They are applied by a special hydraulic 
press, and many variations of form are made to fit special cases. 




Fig. 53. Showing 7-inch Girder Rail, bonded with one Bond. 




Fig. 54. Showing 7-inch Girder Rail, double bonded with two 
Bonds, one on each side of rail. Electrical connection 
of 425,000 cm. 




Fig. 55. Showing 9-inch Grooved Girder Rail double bonded 
with two Bonds, one in each chamber and both on same 
side of rail. Electrical connection of 425,000 cm. 



502 



ELECTRIC STREET RAILWAYS. 




Fig. 56. Showing 9-inch Girder Rail quadruple bonded with 
four Bonds, two in each chamber, on both sides of rail. 
Electrical connection of 850,000 cm. 

Another form of this type of bond is that shown in Fig. 59, as made by the 
Forest City Electric Co. of Cleveland. 



CT\ 



CT\ 






1 

Fig. 57. 

Still another form of concealed bond is shown in Fig. 58, and made by 
I. M. Atkinson & Co., Chicago. 

Rail Bond of X. HO.. Atkinson & Company, Cliicag-o. 





Fig. 58. Applied either single or double under fish-plate. 



TRACK RETURN CIRCUIT. 



503 



In some types of bond the plug lias a hole through it, and after placing 
it in the hole in the web of the rail a steel mandrel is driven through to 
expand the copper outwardly to fill the hole. 

Forest City Electric Company Short Bond. 

This bond is applied underneath the fish-plate, and secured by a special 
tool. 




Fig. 59. 



504 



ELECTRIC STREET RAILWAYS. 



In numerous tests of rail bonds, Mr. W. C. Burton, of the J. G. White Co., 
says it was found that where the copper plug was -well pressed home the 
resistance of the joint between rail and bond did not exceed that of three- 
eighths inch of the bond itself, even after a year or more of use ; and that 
short bonds, especially those that could be covered by the fish-plate 
made rail-joint resistance a very small percentage of the total track resist- 
ance, lie had never found tinned copper any better than the bare metal, 
and when pressed tight had not noticed any effect whatever from local action . 

Table Showing* Sectional Areas of Various Rails, the 
Equivalents in Circular Mils, and tlie Equivalent Cir- 
cular Mils of Copper Giving* Same Conductivity. 

(Figures on rails are for one side of a single track.) 



Weight 
Per Yard. 


Area of 

Single Rail. 

Sq. in. 


45 


4.4095 


50 


4.8904 


56 


5.4874 


60 


5.8794 


65 


6.3693 


70 


6.8592 


80 


7.S392 



Circular Mils of 
Single Rail. 



5,614,400 
6,238,200 
6,986,700 
7,485,800 
8,109,600 
8.733,400 
9,981,100 



Equivalent Circular 

Mils of Copper for 

Same Conductivity. 

Conductivity.* 



997,200 
1,108,000 
1,241,000 
1,329,500 
1,440,400 
1,551,200 
1,772,800 



* For commercial steel rail use .6 these values. 

. ~. , TM 1,000,000 x wgt. per yard 

Area in Cir. Mils = — * ni CL n ?„„. 

10.2052 X .7854 

Area in cir. mils 



Equivalent Cir. Mils of Copper = 



5.63 



Mr. W. C. Burton, of J. G. White Co., found a very considerable difference 
in rail resistivity, and numerous tests of modern steel rails showed the spe- 
cific resistance to be from six to twelve times that of copper, where six has 
been the factor frequently used. In his own practice Mr. Burton uses a 
factor dependent upon the chemical properties and the physical treatment 
of the rail in the rolling-mill. 



BOARD OF TRADE REGILATIOIiri. 



for Great Rritain. 

Regulations prescribed by the Board of Trade under the provisions of 
Section of the Tramways Act, 189—, for regulating the employ- 
ment of insulated returns, or of uninsulated metallic returns" of low resist- 
ance ; for preventing fusion or injurious electrolytic action of or on <»as or 
water pipes, or other metallic pipes, structures, or substances ; and for min- 
imizing, as far as is reasonably practicable, injurious interference with the 
electric wires, lines, and apparatus of parties other than the company, and 
the currents therein, whether such lines do or do not use the earth as a 
return. 

Definitions. 

In the following regulations : — 

The expression " energy " means electrical energy. 

The expression "generator" means the dynamo or dynamos or other 
electrical apparatus used for the generation of energy. 



BOARD OF TRADE REGULATIONS. 505 

The expression "motor" means any electric motor carried on a car and 
used for the conversion of energy. 

The expression "pipe" means any gas or water pipe, or other metallic 
pipe, structure, or substance. 

The expression "wire" means any wire apparatus used for telegraphic, 
telephonic, electrical signaling, or other similar purposes. 

The expression "current" means an electric current exceeding one- 
thousandth part of one ampere. 

The expression " the company " has the same meaning or meanings as in 
the Tramways Act. 189—. 

Regulations. 

1. Any dynamo used as a generator shall be of such pattern and con- 
struction as" to be capable of producing a continuous current without appre- 
ciable pulsation. 

2. One of the two conductors used for transmitting energy from the gen- 
erator to the motors shall be in every case insulated from earth, and is 
hereinafter referred to as the " line"; the other may be insulated through- 
out, or may be insulated in such parts and to such extent as is provided in 
the' following regulations, and is hereinafter referred to as the " return." 

3. Where any rails on which cars run, or any conductors laid between or 
within three feet of such rails, form any part of a return, such part may be 
uninsulated. All other returns or parts of a return shall be insulated, 
unless of such sectional area as will reduce the difference of potential be- 
tween the ends of the uninsulated portion of the return below the limit 
laid down in Regulation 7. , . , x. * 

4. When any uninsulated conductor laid between or within three feet of 
the rails forms any part of a return, it shall be electrically connected to 
the rails at distances apart not exceeding 100 feet, by means of copper 
strips having a sectional area of at least one-sixteenth of a square inch, or 
by other means of equal conductivity. 

5. When any part of a return is uninsulated it shall be connected with 
the negative terminal of the generator, and in such case the negative termi- 
nal of the generator shall also be directly connected, through the current- 
indicator hereinafter mentioned, to two separate earth connections, which 
shall be placed not less than twenty yards apart. 

Provided that in place of such two earth connections the company may 
make one connection to a main for water supply of not less than three 
inches internal diameter, with the consent of the owner thereof, and of the 
person supplying the water ; and provided that where, from the nature of 
the soil or for other reasons, the company can show to the satisfaction of an 
inspecting officer of the Board of Trade that the earth connections herein 
specified cannot be constructed and maintained without undue expense, the 
provisions of this regulation shall not apply. 

The earth connections referred to in this regulation shall be constructed, 
laid, and maintained so as to secure electrical contact with the general 
mass of earth, and so that an electromotive force not exceeding four volts 
shall suffice to produce a current of at least two amperes from one earth 
connection to the other through the earth, and a test shall be made at least 
once in every month to ascertain whether this requirement is complied 
with. 

No portion of either earth connection shall be placed within six feet of 
any pipe, except a main for water supply of not less than three inches in- 
ternal diameter, which is metallically connected to the earth connections 
with the consents hereinbefore specified. 

6. When the return is partly or entirely uninsulated, the company shall, 
in the construction and maintenance of the tramway (a), so separate the 
uninsulated return from the general mass of earth, and from any pipe in 
the vicinity ; (b) so connect together the several lengths of the rails ; (c) 
adopt such rneans for reducing the difference produced by the current be- 
tween the potential of the uninsulated return at any one point and the po- 
tential of the uninsulated return at any other point ; and (77) so maintain 
the efficiency of the earth connections specified in the preceding regulations 
as to fulfill the following conditions, viz.: 



506 ELECTRIC STREET RAILWAYS. 

(1.) That the current passing from the earth connections through the in- 
dicator to the generator shall not at any time exceed either two amperes 
per mile of single tramway line, or 5 per cent of the total current output of 
the station. ' 

(2) That if at any time and at any place a test he made hy connecting a 
galvanometer or other current indicator to the uninsulated return, and to 
any pipe in the vicinity, it shall always he possible to reverse the direction 
of any current indicated by interposing a battery of three Leclanche cells 
connected in series, if the direction of the current is from the return to the 
pipe, or by interposing one Leclanche cell, if the direction of the current is 
from the pipe to the return. 

In order to provide a continuous indication that the condition (1) is com- 
plied with, the company shall place in a conspicuous position a suitable, 
properly connected, and correctly marked current indicator, and shall keep 
it connected during the whole time that the line is charged. 

The owner of any such pipe may require the company to permit him at 
reasonable times and intervals to ascertain by test that the conditions 
specified in (2) are complied with as regards his pipe. 

7. When the return is partly or entirely uninsulated, a continuous record 
shall be kept by the company of the difference of potential during the work- 
ing of the tramway between the points of the uninsulated return furthest 
from and nearest to the generating station. If at any time such difference 
of potential exceeds the limit of seven volts, the company shall take imme- 
diate steps to reduce it below that limit. 

8. Every electrical connection with any pipe shall be so arranged as to 
admit of easy examination, and shall be tested by the company at least once 
in every three months. 

9. Every line and every insulated return or part of a return, except any 
feeder, shall be constructed in sections not exceeding one half of a mile in 
length, and means shall be provided for insulating each such section for 
purposes of testing. 

10. The insulation of the line and of the return when insulated, and of all 
feeders and other conductors, shall be so maintained that the leakage cur- 
rent shall not exceed one-hundredth of an ampere per mile of tramway. 
The leakage current shall be ascertained daily, before or after the hours of 
running, when the line is fully charged. If at any time it should be found 
that the leakage current exceeds one-half of an ampere per mile of tram- 
way, the leak shall be localized and removed as soon as practicable, and the 
running of the cars shall be stopped unless the leak is localized and removed 
within twenty-four hours. Provided, that where both line and return are 
placed within a conduit this regulation shall not apply. 

11. The insulation resistance of all continuously insulated cables used for 
lines, for insulated returns, for feeders, or for other purposes, and laid be- 
low the surface of the ground, shall not be permitted to fall below the 
equivalent of 10 megohms for a length of one mile. A test of the insulation 
resistance of all such cables shall be made at least once in each month. 

12. Where in any case in any part of the tramway the line is erected over- 
head and the return is laid on or under the ground, and where any wires 
have been erected or laid before the construction of the tramway, in the 
same or nearly the same direction as such part of the tramway, the com- 
pany shall, if required to do so by the owners of such wires or any of them, 
permit such owners to insert and maintain in the company's line one or 
more induction coils, or other apparatus approved by the company for the 
purpose of preventing disturbance by electric induction. In any case m 
which the company Avithhold their approval of any such apparatus, the 
owners may appeal to the Board of Trade, who may, if they think fit, dis- 
dispense with such approval. 

13. Any insulated return shall be placed parallel to, and at a distance not 
exceeding three feet from, the line, when the line and return are both 
erected overhead, or 18 inches when they are both laid underground. 

14. In the disposition, connections, and working of feeders, the company 
shall take all reasonable precautions to avoid injurious interference with 
any existing wires. 

15. The company shall so construct and maintain their systems as to 
secure good contact between the motors, and the line and return respec- 
tively. 



BOARD OF TRADE REGULATIONS. 507 



16. The company shall adopt the best means available to prevent the oc- 
currence of undue sparking at the rubbing or rolling contacts in any place, 
and in the construction and use of their generator and motors. 

17. In working the cars the current shall be varied as required by means 
of a rheostat containing at least twenty sections, or by some other equally 
efficient method of gradually varying resistance. 

18. Where the line or return or both are laid in a conduit, the following 
conditions shall be complied with in the construction and maintenance of 
such conduit : 

(a) The conduit shall be so constructed as to admit of easy examination of, 

and access to, the conductors contained therein, and their insulators 
and supports. 

(b) It shall be so constructed as to be readily cleared of accumulation of 

dust or other debris, and no such accumulation shall be permitted to 
remain. 

(c) It shall be laid to such falls, and so connected to sumps or other means 

of drainage as to automatically clear itself of water without danger 
of the water reaching the level of the conductors. 

(d) If the conduit is formed of metal, all separate lengths shall be so jointed 

as to secure efficient metallic continuity for the passage of electric 
currents. Where the rails are used to form any part of the return, 
they shall be electrically connected to the conduit by means of cop- 
per strips having a sectional area of at least one-sixteenth of a square 
inch, or other means of equal conductivity, at distances apart not ex- 
ceeding 100 feet. Where the return is wholly insulated and contained 
within the conduit, the latter shall be connected to earth at the gen- 
erating station through a high resistance galvanometer, suitable for 
the indication of any or partial contact of either the line or the return 
with the conduit. 

(e) If the conduit is formed of any non-metallic material not being of high 

insulating quality and impervious - to moisture throughout, and is 
placed within six feet of any pipe, a non-conducting screen shall be 
interposed between the conduit and the pipe, of such material and 
dimensions as shall provide that no current can pass between them 
without traversing at least six feet of earth; or the conduit itself shall 
in such case be lined with bitumen or other non-conducting damp- 
resisting material in all cases where it is placed within six feet of any 
pipe. 
(/) The leakage current shall be ascertained daily before or after the hours 
of running, when the line is fully charged, and if at any time it shall 
be found to exceed half an ampere per mile of tramway, the leak shall 
be localized and removed as soon as practicable, and the running of 
the cars shall be stopped unless the leak is localized and removed 
within 24 hours. 

19. The company shall, so far as may be applicable to their system of 
working, keep records as specified below.' These records shall, if and when 
required, be forwarded for the information of the Board of Trade. 

Daily Records. 

Number of cars running. 

Maximum working current. 

Maximum working pressure. 

Maximum current from earth connections (vide Regulation 6 (1) ). 

Leakage current (vide Regulation 10 and 18/.). 

Fall of potential in return (vide Regulation 7). 

Monthly Records. 

Condition of earth connections (vide Regulation 5). 
Insulation resistance of insulated cables (vide Regulation 11). 

Quarterly Records. 

Conductance of joints to pipes (vide Regulation 8). 



508 ELECTRIC STREET RAILWAYS. 

Occasional Records. 

Any tests made under provisions of Regulation 6 (2) ). 
Localization and removal of leakage, stating time occupied. 
Particulars of any abnormal occurrence affecting the electric working 
of the tramway. 

Signed by order of the Board of Trade this day of 189 



Assistant Secretary, Board of Trade. 



OVERHEAD SYSTEM EOR ELECTRIC STREET 
RAILWAYS. 

1. Ladder system, shown in the following cut, formerly somewhat used on 
small roads, where both feeder and trolley wire of the same size would carry 
the load. Feeder in this case is simply an enlargement of the trolley wire, 
and as used might have better been one large trolley wire. 



TROLLEY WIRE 



TRACK RETURN 
~ CIRCUIT 



Fig. 60. 



2. A modification of the above system is the following. In this second 
system the trolley wire is cut into sections, and while losing the extra con- 
ductivity of the continuous trolley, by placing fuse and switch at the junc- 
tion of each sub-feeder with the main feeder, each such section may be cut 
out in case of trouble without depriving the remainder of the system of 
current. 



TROLLEY IN SECTIONS 



33. 



TRACK RETURN 
CIRCUIT 



Fig. 61. 



Both above systems are now somewhat out of date, although occasion- 
ally used on the smaller roads. 

3. The system shown in the following cut is more of a real feeding system 
than either of the previous two. 

The trolley wire is connected directly to the dynamo, but is also fed at 
various points, as at a, b, c, by larger wires tapped into it. 

A load at d would thus receive current from both feeders b and c, and the 
pressure can be more evenly maintained than by either of the previous 
methods. By making the trolley wire of larger cross-section than is usual 
in the previous systems, it is possible to have fewer sections and yet main- 
tain a fairly even voltage. 



OVERHEAD SYSTEM. 



509 




Fig. 62. 



4. An obvious modification of the above is shown in the following cut. 
In this system the trolley wire is again divided into sections, but each sec- 
tion is supplied from its own separate feeder, the size of which may be so 
calculated as to keep a very even pressure at all points on the line, especially 
so if the trolley wire be not too small and the sections not too long. It is 
of course, subject to the objection that the sections receive no help from the 
remainder of the circuit, but has the advantage that each section may be 
controlled by switch and circuit-breaker at the station, and if at any part of 




•TRACK RETURN 
CIRCUIT 



Fig. 63. 



the system, as at d, there is a heavy grade or a heavy massing of cars, cross 
connection can be made to the feeder c, either by switch or by permanent 
tie. Another method of tying that has been used in some localities is that 
of connecting the ends of trolley sections together with a small copper wire, 
say No. 12 B. & S., and thus getting part current both ways ; and in case of 
heavy overload oi short circuit on a section the tie- wires will burn off, leaving 
all other sections free as before. This method is said to be of consider- 
able advantage. 

5. The following cut shows a combination of the previous methods, such 
as results from experience in operating larger systems of roads. The 
principal feeder C is tapped at intervals to feed the short and long sections, 
and in order to maintain even voltage at its distant end, is reinforced at 
d and e by the feeders E and F, while the still farther distant trolley-line 
sections are fed by the long feeders G and H, which can be joined as at/, if 
the circumstances call for it. 

As mentioned above, this method is the result of actual experience on a 
line after it has been run, and the loads have developed the points where 
current is most needed. While systems of overhead lines are always laid out 
with more or less care, traffic often takes the most erratic changes in direc- 
tion, and changes its call for current to such an extent that feeders often 
have to be run to new points, sections have to be joined or new divisions 
made, or feeders bave to be tied ; and this cut shows the general result of 
such actual experience. As a general thing it is not good practice to cut 
the trolley into any more sections than necessary for safety ; and even then 
a separable line, that is. one that can be cut into sections by switches, is 
better than separate sections. 



510 



ELECTRIC STREET RAILWAYS. 




Fig. 64. 

6. For long roads the system shown in the following cut may be used 
with advantage, as, with heavy trolley wire such as should always be used 
on long lines, the trolley wire can be reinforced by the feeders as shown, so 




TROLLEY WIRE 



TRACK RETURN 
CIRCUIT 



Fig. 65. 

as to maintain a fairly constant pressure, and advantage be taken of all the 
conductivity of the system. On double-track roads all the trolley system 
should be united and at frequent intervals, so that advantage may be taken 
of the full conductivity installed. 

7. A system sometimes vised on small single-track lines, where feeders are 
not entirely necessary, but a single trolley wire may be too small, is to run 
two trolley wires side by side, and at all sidings the wire nearest the siding 
is run around it, and the cars can pass and the trolleys follow each its own 
wire without troublesome switches. 



CAXCTJIiATIHT*} THE COIfBUCTOC} IYITEM. 



Dr. Louis Bell gives the following steps as the best to be followed in 
entering upon the calculation of the conducting system of a trolley road : 

1. Extent of lines. 

2. Average load on each line. 

3. Center of distribution. 

4. Maximum loads. 

5. Trolley wire and track return. 

6. General feeding system. 

7. Reinforcement at special points. 

It must be said at once that experience, skill, and good judgment are far 
better than any amount of theory in laying out the conducting system of 
any road. 

Much depends upon the character of the load factor, i. e., the ratio of 
average to maximum out-put ; and this, varying from .3 to .6, can only be 
guessed at by a study of the particular locality, the nature of its industries 
and working people, the shape of the territory, and the nature of the sur- 
rounding country. 



CALCULATING CONDUCTING SYSTEM. 511 

1. Map out the track to scale, noting all distances carefully, and dot in 
any contemplated extensions, so that adequate provision may be made in 
the conducting system for them. Note all grades, giving their length, gra- 
dient, and direction. Divide the road into sections such as may best sug- 
gest themselves by reason of the local requirements, but such as will make 
the service under ordinary conditions fairly constant. 

2 The average load on each section will depend, of course, upon the 
number of cars, and tbe number of cars upon the traffic. This can only be 
arrived at by a comparison with similar localities already equipped with 
street railway and even then considerable experience and keen judgment 
of the general nature of the towns are necessary in arriving at anything like 
a correct result. . 

3 If the road has been correctly laid out as to sections, the load on each 
will be uniform and may be considered as concentrated at a point midway 
in each section. Now, if a street railway were to be laid down on a perfectly 
level plain, where the cost of real estate was the same at all points, and 
wires could be run directly to the points best suited ; then it would only be 
necessary to locate the center of gravity of the entire system, and build the 
power station at that point, sending out feeders to the center of each sec- 
tion. Unfortunately for theory, such is never the case ; and cost of real 
estate, availability of the same, convenience of fuel, water, and supplies 
will govern very largely the selection of a location for the power-house. 
Even when all the above points necessitate the placing of the power-house 
far from the center of gravity of a system, it may be possible to use such 
center as the distributing point for feeder systems, and even where this is 
not possible, it is well to keep in mind the center, and arrange the distribut- 
ing system as nearly as possible to fit it. 

All this relates, however, to preliminary determinations for the system as 
determined at the time, and in large systems will invariably be supplemented 
by feeders, run to such points as the nature of the traffic demands. A base- 
ball field newly located at some point on the line not known to the engineer 
previous to the installation, will require reinforcement of that particular 
section ; and often after a road has been running for some time, the entire 
location of traffic changes, due to change in facilities, and feeder systems 
then have to be changed to meet the new conditions, so that after all, loca- 
tion of the center of distribution depends largely on judgment. 

4. The predetermination of the maximum or average load is another mat- 
ter for experienced guessing, as it will depend altogether upon the nature 
of the traffic, how many people patronize the line, and how often the cars 
are run. 

If the weight of the car and its load be known it is an easy matter to de- 
termine the power necessary to propel it ; and tables will be found in this 
section showing the tractive effort necessary, and all other data for such 
determination. 

Bell gives the following formula for the horse-power necessary at the 
wheel of a car. 

Let P = total horse-power. 

W= weight of car and load in tons. 

.43 =: h.p. per ton required at wheel at 20 lbs. per ton for a 

speed of 8 miles per hour. 
G = per cent grade. 



Then 



P — W(A3 + A3G). 



This applies to straight tracks only, and at a speed of 8 miles per hour, 
which is often exceeded. 

The same authority also states that allowing an efficiency between trolley 
and car-wheel of 66f per cent, and voltage at the car of 500, 1\ amperes per 
ton plus li amperes per ton for each per cent of grade will be approximately 
correct. This means an average of about 15 amperes per car, throughout 
the day, for the ordinary car and road. Long double-truck cars will take 
nearer 25 amperes, and in the writer's judgment this last is a good average 
to use for all traffic on ordinary street railways. 

The maximum current will rise to four or five times the average where 
tut one or two cars are in use ; will easily be three times the average on 



512 ELECTRIC STREET RAILWAYS. 

roads of medium size, while on very large systems it may not be more than 
double the average. If speeds are maintained on heavy grades the maxi- 
mum is still further liable to increase. 

Another point to be considered in connection with maximum load, is the 
location, not only of heavy grades, but of parks, ball-grounds, athletic 
helds, cemeteries, and other such places for large gatherings of people that 
are liable to call for heavy massing of cars, many of which must be started 
practically at the same time, and lor which extra feeder, and in some cases 
extra trolley capacity, must be provided. 

Having determined the average current pen section of track, the maximum 
for the same, and the extraordinary maximum for ends, park locations etc 
as well as the distances, all data are obtained necessary for the determina- 
tion of sizes of feeders. 

5. The selection of the proper size of trolley is somewhat empirical, but 
the size may be governed by the amount of current that is to be carried It 
is obvious that Avith given conditions the larger the trolley wire the fewer 
feeders will be necessary, and yet with few feeders the voltage is liable to 
vary considerably, li^ ordinary practice of to-day No. JB. & S. and No. 00 
B. & S. gauge, hard-drawn copper are the sizes mostly in use, the latter on 
those roads having heavier traffic or liable to massing of cars at certain 
localities. On suburban roads using two trolley wires in place of feeders, 
0000 B. & S. gauge will probably be best. 

Track return circuit has been treated fully in a previous chapter; and all 
that is needed to say here is, that some skill in judgment is necessary in 
settling on the value of the particular track return that may be under con- 
sideration, in order to determine the value of the constant to be used in the 
formula for computing the size of wire or overhead circuit. In ordinary 
good practice this value may be taken as 13, 14, or 15, according as the bond- 
ing and rail dimensions are of good type and large. 

6. Feeder-points should, in a general way, be so located as to allow no 
drop in a section of trolley wire exceeding 5 per cent or 25 volts under nor- 
mal load. This drop is easily determined by the regular formula : 

Let D = distance from feeding point to end of the trolley section, 
cm. = circular mils of the trolley, 
E = drop in volts, 
13 := constant for circuit in connection with a Avell bonded heavy 

track, 
Iz= current required per car, usually taken as 15 amperes under 
running conditions, but more safely taken as 25 amperes. 
Then 

^~ 13/ ' 

and if the trolley wire selected be No. 00 B. & S. cm. ■=. 133,600, and as the 

133 000 X 25 
maximum drop permissible in the trolley wire is 25 volts D = — ' — 

JLo X 40 

= longest section of trolley wire for one car, or 10,231 feet. If two cars are 
bunched at the end of the section the drop will be twice as great, or the 
length of section can be but 5,115 ft.; for 3 cars the length will be 3,410 ft.; 
for 4 cars the length will be 2,558 ft.; and for five cars the length will be 
2,046 feet. 

The above calculation will be correct for level roads and where the load is 
well distributed ; but the trolley-wire sections must necessarily be shortened 
up for grades or at such points in the line as heavy massing of cars is liable 
to take place, as at ball-parks, etc., where people all want to get home at 
once, and all available cars are started from that point. 

In such cases it will probably be safe to allow 50 amperes per car for the 
section of trolley wire on which the park is located, and the result is then 

1 VI 000 v 2^ 
D — ' A = 5,115 ft. for one car, and for n cars the greatest length 
13 X 50 

of section would be 5,115 -j- n. 



CALCULATING CONDUCTING SYSTEM. 



513 



Having calculated all the points on the trolley line at which it should be 
fed, it remains to calculate the size of feeder for the purpose. 

As to the allowable drop in feeders, it is not well to have over 100 volts 
total drop at the car and 75 volts total drop is better under maximum load, 
as low voltage at the motors tends to over-heat them to a dangerous degree. 
Much of the regular drop can be overcome by over-compounding the gene- 
rators for a rise of potential of about 50 volts. 

It is decidedly better practice to make feeder determinations based on the 
maximum load, as the average load will easily care for itself, but during 
times of extraordinary crowds, or snow-storms, if the line has not been cal- 
culated for such heavy loads, all the motors will heat, and much trouble 
is liable all along the line. 

The writer considers 75 volts drop in feeders under maximum load condi- 
tions a safe basis, together with 35 amperes per car for all those liable to 
be on the section at once. Over-compounding will make up for 50 volts of 
the drop at the motors at times of heaviest distributed load, so there will 
be no danger. Feeder calculation will then be 

. . , 13 x D X 35 n cars 

cm. of feeder = — • 

75 
It is quite obvious that the current-carrying capacity of the feeder must 
be taken into consideration, in spite of any determination of drop ; and this 
can be found in the chapter on Conductors. Sizes of conductors are also 
governed to some extent by convenience in handling, and it is found that 
1,000,000 c. m. is about the largest that can be safely handled for under- 
ground work, while anything larger than 500,000 c. m. for overhead circuits 
is found to be difficult to handle. 

7. In cases where it is necessary to feed the trolley wire in short sections, 
in order to reinforce the trolley wire for heavy grades, sub-feeders are often 
used, the main feeder being tapped into its center, or at such point in its 
length as will give the best distribution, as shown in the following cut. 



SUB-FEEDER 



HEAVY GRADES &C 



d 



TRACK RETURN 
CIRCUIT 



Fig. 66. 
For lines having parks at the end, or in fact for any such section, it is 
perhaps best to run a feeder nearly to the end of the section, then take the 
trolley line to the feeder at various points comparatively short distances 
apart, as shown in the following cut; and if the loads are at times especially 
heavy, the next feeder can be made to assist by cross-connecting, as at d. 



O > . 



BALL PARK AT END OF LINE 



TRACK RETURN 
CIRCUIT 



Fig. 67. 

In this connection it must be remembered that heavy loads from parks, 

as well as on grades, do not often come at the same time as heavy loads on 

other sections, and therefore that the over-compounding may not be but a 



514 



ELECTRIC STREET RAILWAYS. 



part of the full-load rise, and it is best under the circumstances to calculate 
the sizes of such feeders for a smaller drop, say 50 volts maximum instead 
of 75. 

In general it may be said that it is now tbe usual practice to use a few 
standard sizes of feeder wire, such as 100,000 cm., 200,000, 250,000, 500,000, 
and so connect them as to produce the required results, rather than to 
carry a large number of various sizes of wire in stock. In fact, this same 
practice is now carried out in large lighting installations as well, and in 
those constant pressure is much more necessary than in railway circuits. 

Special methods of Distribution. 

For cases requiring excessively large currents carried a considerable dis- 
tance, or for ordinary currents carried excessive distances, it is usually 
economy to adopt some special method ; and among those most commonly 
mentioned are : the three-wire system, the booster system, the substation 
system. 

Three-Wire System. This system, patented some time ago by the 
General Electric Company, has been seldom used, and where used has met 
with little success, owing to the difficulty met in keeping the system bal- 
anced. 

The diagram below will assist in making the method plain. Two 500-volt 
generators are used, as in the lighting system of the same type. The rail 
return is used as the neutral conductor; and if both trolley wires could be 
made to carry the same loads, and to remain balanced, then the rail return 





1 ! 




c 
c 


> 
1 


1 J 


; 








~~l i 





THREE WIRE SYSTEM 

Fig. 68. Three-Wire System. 



would carry no current, and no trouble would occur from electrolysis. The 
overhead conductors could also be very much smaller, as currents would 
be halved, and the full voltage would be practically 1000. 

The Booster System. — Where current must be conveyed a long 
distance, say five to ten miles, and be delivered at 500 volts, it is hardly 
good economy to install copper enough to prevent the drop; and if the volt- 
age of the generator be raised sufficiently to deliver the required voltage, 
the variations due to change of load will be prohibitive. 

In such cases a "booster" can be connected in series with the feeder, 
and automatically keep the pressure at the required point, as long as the 
generator delivers the normal pressure. 

The "booster" is nothing more than a series-wound dynamo, connected 
so that all the current of the feeder to which it is attached flows through 
both field and armature coils, and the voltage produced at the armature 
terminals is added to that of the line, and as the voltage so produced is in 
proportion to the current flowing, it will be seen that the pressure will rise 



CALCULATING CONDUCTING SYSTEM. 



515 



and fall with the current. This is now used in many instances, both in 
lighting and for railway feeders, and especially in feeding storage batteries, 
and has met with entire success. The following cut is a diagram of the 
connections. 



6 TO TO MILES 



MOTOR 
TO DRIVE 
GENERATORXBOOSTEF 




DROP AT FULL LOAD 25 VOLTS 



RISE AT FULL LOAD 95 VOLTS 



Q 



500 VOLTS 
1 



OVERHEAD RETURN 

BOOSTER SYSTEM 
FIG. 69. 



Return Feeder Booster. —Major Cardew, Electrical Engineer for 
the Board of Trade, some time ago devised a method of overcoming exces- 
sive drop in track return circuits by the use of insulated return feeders, in 
series with which he placed a booster. 

The booster draws current back toward the station, adding its E.M.E. to 
that in the feeder. Cardew used a motor generator, the series field of 
which was separately excited by the outgoing feeder for the same section of 
road. Thus the volts "boosted" were indirect proportion to the current 
flowing. H. F. Parshall, in adopting the return feeder booster for some of 
his work in England, used a generator in place of the motor-generator of 
Major Cardew, exciting the field by the current flowing out on the trolley 
feeder, thus producing volts in the armature in proportion to the current 
flowing. The following diagram shows Parshall' s arrangement. 




TROLLEY WIRE 



^- (SEPARATELY EXCITED) 

4- 'generator i 



BUS BARS AT STATION 



FlG. 70. Modification of Major Cardew's System of Track Return 
Booster for Preventing Excessive Drop in Bail Return Circuits. 



516 



ELECTRIC STREET RAILWAYS. 



Su1»-Station System. — Where traffic is especially heavy, and a rail- 
way system widespread, it is now the practice to use 'one large and very 
economical power station with high-pressure generators, now invariably 
polyphase alternators, and to distribute this high-pressure alternating 
current to small sub-stations centrally located for feeding their districts, 
and there changing the current by means of static and rotary transformers 
into continuous current of the requisite pressure, in the case of railways 
500 or 550 volts. Such systems have already been mapped out for the Man- 
hattan Elevated Railway, and for the Metropolitan Traction Company of 
New York, and are now in operation, as well as on the Central Underground 
Railway of London. 

The following diagrams will assist in making the system plain. 



SUBSTATION 
NO. 1 



STATIC 
TRANS- 
FORMERS 







DISTRIBUTION FROM 
SUB-STATIONS 



Fig. 71. 

TESTS OF STREET RAILWAY CIRCUITS. 

The following tests are condensed from an article by A. B. Herrick in the 
Street Railway Journal, April, 1899. 
The following instruments will be required : 

A barrel water rheostat to take say 100 amperes. 
A voltmeter reading to GOD volts. 
A voltmeter reading to 125 volts. 
An ammeter reading to say 150 amperes. 

A pole long enough to reach the trolley wire, with a wire running along it 
having a hook to make contact. 

Use one generator at the station, and have the attendant keep pressure 
constant. 



Test for Drop and Resistance in Overhead lines and 
Returns. 

The car containing the above equipment of instruments is run to the end 
of the section of conductor which it is desired to test, where a line circuit- 
breaker divides the sections. 

The instruments are then connected as shown in Fig. 73. 

It is clear now that if the switch G be closed, current will flow throngh 
the rheostat and be measured by the ammeter. We now have the trolley 
and feeder B for a pressure wire back to the station, and the reading of 
voltmeter C therefore gives the drop between the station and the point A 



TESTS OF STREET RAILWAY CIRCUITS. 

I I 



sir 




518 



ELECTRIC STREET RAILWAYS. 



in the feeder and trolley carrying the load. Voltmeter D shows the drop 
across the rheostat ; and if the sum of readings C and.D be deducted from the 
station pressure, the difference will be the drop in the ground return. 



AMMETER 



'^A/WH 




,WHEEL,OR TRACK 
CONTACT 



Fig. 73. 

The station pressure can be taken by changing the lead of voltmeter C 
down to F as shown by the dotted line. 

The drop on A and its resistance having been found, the trolley-pole can 
be swung around and the same data be determined for the circuit B. 



To Read the Ground Return Drop Directly. 

« 

Open the station switch on that feeder that is being used as pressure wire, 
and ground the feeder to the ground bus through a fuse for safety. 

Connect the instruments as shown in the following cut ; then when the 
switch G is closed and current flows, the drop from A to F read on voltmeter 
C will be the drop in the ground return from F to X. 




Fig. 74. 



TESTS OF STREET RAILWAY CIRCUITS. 



19 



To Determine Drop at End of line. 

For use on double-track lines only, unless a pressure wire can be run to 
the end of line from the last line circuit-breaker. 

Break all cross connections from feeder to trolley-wire for one track, as 
at n ; connect this idle trolley to the next one back toward the station, as 
at C, then make the tests as in the two methods described above, connections 
being shown in the following cut. 




Fig. 75. 



To Determine the Condition of Track Bonding*, and the 

Division of Return Current through Rails, Water 

or Gas Pipes, and Ground. 

The cut below shows the connections for this test as applied to a single 
track, or to one track of a double-track road. 

Ground the feeder A at the station, or rather connect it to the ground bus 
through a fuse. Then connect the track at C to A by the pole E through 
the ammeter M. The drop between points F and D will be the drop through 
the rail circuit between C and D, due to the current flowing. 

If connection be made to a hydrant, or other water connection, and to a 
gas-pipe, as at X, still retaining the rail connection at C, more current will 



6 



AM METER ffl 




Fig 76 



ao 



ELECTRIC STREET RAILWAYS. 



flow through ammeter M, due to providing the metallic return through A 
for the water-pipe, and the first reading of the ammeter M is to the second 
reading as the resistance of the water-pipe is to that of the rail return, and 
the current returning to the station will distribute itself between the two 
paths in proportion to the readings mentioned. If ammeter G be read at the 
same time, the difference between its reading and the sum of the other 
two readings will be the amount of current returning by other paths than 
the rail and water-pipe. If C is near the station it may be necessary to 
break the ground connection between rails and bus, so that all current may 
return over the metallic circuit A. 

To determine condition of bonds, move the contact C back towards D, and 
the decrease in drop as shown by the vm. will be very nearly proportional 
to the length of track, except where a bad or broken bond may be located, 
Avhen the change will be sudden. 






TEiTIDTO RAIL BOID§. 

It is not commercially practicable to measure the exact resistance of rail 
joints, as such resistance is small under ordinary circumstances, and all the 
conditions vary so much as to prevent accurate measurement being made. 
The resistance of rail joints is therefore measured in terms of length of the 
rail itself, and there are numerous instruments devised for the purpose, 
nearly all being based upon the principle of the wheatstone bridge, the 
resistance of the rail joint being balanced against a section of the rail, as in 
the following diagram. 



K>^_ 




L< 



MILLI-VOLTMETER 
CENTER-ZERO 



Y 2 OHM 



Fig. 77. Diagram of Method of Testing Rail Joints. 



A Weston or other reliable milli-voltmeter, with the zero point in the mid- 
dle of the scale, is the handiest instrument for making these tests. The 
points b and c are fixed usually at a distance of 12 inches apart, the point a 
is then moved along the rail until there is no deflection of the needle when 
both switches are closed. The resistance of the joint or the portion between 
the points b and c is to that of the length, x, inversely as the length of the 
former is to that of the latter, all being in terms of the length of rail, or, 
Let 

x = distance in inches between points a and c, 
y = distance between the points c and b, 
v = resistance of joint in terms of length of rail, 
then, 



TESTING RAIL JOINTS. 



521 



and if x = 36 inches and y 
then 



12 inches, 



12 



3 times its length in rail. 



Another scheme for testing rail joints is pointed out by W. N. Walmsley 
in the " Electrical Engineer," December 23, 1897. 

In the following cut, the instrument is a specially designed, double milli- 
voltmeter, both pointers having the same axis, and indicating on the same 
scale. 



DOUBLE 
MILIVOLTMETER 




WALMS LEY'S RAIL TESTER 



FIG. 78. 



The points ab are at a fixed distance d, the point c being movable along 
the rail. Points a and b are set on the rail astride the joint, as shown ; the 
point c is then moved along the rail until the pointers on the instrument 
coincide, indicating the same drop. Then the resistance of x is the same 
as d, in terms of the size of rail used. 

Harold P. Brown has devised an instrument for testing rail joints with 
little preparation. It consists of two specially shielded milli-voltmeters of 
the Weston Company's make, put up in a substantial wooden case, the top 
of which is made up in part of two folding legs which, when unfolded, cover 
six feet of rail. These legs form one length, which is divided by slots into 
two lengths, one of one foot, the other five feet long. The instrument is 
placed alongside the track in such position that the leg rests on the rail, and 
the joint to be tested is between the ends of the shorter branch or leg, while 
five feet of clear rail are included between the ends of the longer leg. 

The instrument terminals are connected to small horseshoe magnets, that 
fit into the slots in each leg, and when rested on the rail always make the 
same pressure of contact, the poles being amalgamated and coated with a 
special soft amalgam, called Edison Flexible Solder. 

With the five feet of rail as a shunt, the instrument will read to 1500 am- 
peres. 

There are several separate resistance coils and binding-posts supplied for 
different sizes of rail in common use, so that the dial of the milli-voltmeter 
needs but one scale. 

The second milli-voltmeter measures the drop around the one foot of 
joint, and has coils so arranged to permit of reading .15, 1.5, 15. volts. 

A reading of the current value is taken from the five feet of rail, and a 
simvdtaneous reading of the drop across the joint and one foot of rail is also 
made. The resistance of the latter is then found by ohm's law, 



E = 



522 



ELECTRIC STREET RAILWAYS. 




A B C 

Fig. 79. Brown's Rail-bond Testing Instrument. 



Street Railway Iflotor Testing*. 

Barn test for efficiency : — 

Put a double-flange pulley on the car axle for the application of a prony 
brake, pour water inside the pulley to keep it cool. Use common platform 
scale, as shown in cut. 




Fig. 



Then let Z> =r distance from center of axle to point on scales in feet, 
measured horizontally. 
77 == 3.1416, 

R = revolutions per minute, 
E = voltage at motor, 
1= amperes at motor, 
T— force applied to balance scales, in pounds. 



Then B. H. P. = 



2tt PR T 
33,000 
500 > 



B. H. P. at 500 volts = 
EI 



,. M xf) a 



746 
500 I 
746 

Efficiency of motor = 



33,000 
= E.H.P. supplied to motor. 

= E.H.P. supplied to motor at 500 volts. 



B.H.P. 



B.H.P. at 500 volts 



E.H.P. ~ E.H.P. at 500 volts 



Draw-bar JPull and Efficiency Test Without Removing- 
Motor from Car. 



Rig up lever as shown in cut, being sure the fulcrum A is strong enough 
to stand the pull. Posts, as shown, make good fulcrum ; have turn buckle 
F for taking up any weakness. 



FAULTS AND REMEDIES. 



523 




Fig. 81. 

Let D = diameter of car wheel in feet. 

77 = 3.1416, 

T=z force on scale in pounds, 
L = length of long arm of lever, 
L y = length of short arm of lever, 
It = revolutions per minute. 
Place a jack-screw under each side of the car, and lift the body until there 
is only friction enough between wheels and rail to keep the speed of revolu- 
tions down to the normal rate. 
Then 



and 



Draw-bar pull = T - — ■ 



B.H.P. 



A' 



and the efficiency is the same as before, 

B.H.P. _ . 

i.e. EH P. = efficiency. 



Mr. A. B. Herrick has devised a testing-board for street-railway repair 
shops that will greatly assist in making all inspection tests, and which is 
described in the "Street Railway Journal" for January, 1898, pages 11 
and 12. 

rA€IT§ A1¥I» REMEDIEi. 

Car Will not Ktart : 

a. Turn on lamps ; if they burn, trolley and ground wires are all right 
and current is on line. 

b. If lights die down when controller is thrown on, trouble may be poor 
contact between rails and Avheels, or car may be on " dead " track. 

c. If car works all right with one controller, fault may be open circuit, or 
poor contact in the other. Throw current off at canopy, or pull down the 
trolley and examine the controller. 

d. See that both motor cut-outs are in place. 

e. Fuse may be blown ; throw canopy switch and replace. 

/. See that motor brushes are in place and intact, and make good contact. 

g. Car maybe standing on "dead" or dirty rail ; in either case connect 
wheels to next rail by wire. It is better to open canopy switch while con- 
necting wire to wheels, or a shock may be felt. 

h. Ice on trolley wheel or wire will prevent starting. 



Sparking; at Commutator Brushes: 

a. Brushes may be too loose ; tighten pressure spring. 

b. Brushes may be badly burned or broken, and therefore make poor con- 
tact on the commutator. Replace brushes with new set, and sandpaper 
commutator surface smooth. 



524 ELECTRIC STREET RAILWAYS. 



c. Brushes may be welded to holder, and thus not work freely on commu- 
tator surface. 

d. Commutator may be badly worn and need renewing. 

e. Commutator may have a flat bar, or one projecting above the general 
surface ; commutator must then be turned true in lathe. 

f. Dirt or oil on commutator may produce sparking ; clean well. 

flame at the commutator may be produced by : — 

a. Broken lead wire or coil, producing a greenish flame, and burning two 
bars usually diametrically opposite each other. If left too long the two 
bars will be' badly burned, as will also the insulation between. 

Temporary relief can be had by putting a juniper of solder or of small 
wire across the burned bar, connecting the two adjacent bars to each other ; 
one jumper is enough. 

b. A short-circuited field coil, or a field coil improperly connected, will 
produce flare at commutator. Short-circuited coil can be found by volt- 
meter test across terminals showing drop in coil. Wrong connection can be 
detected by pocket compass. 

Incandescent Lamps sometimes burn out or break. Replace with 
new ones. If they do not burn when switch is on, 

a. Examine each for broken filament. 

b. Examine for poor contact in socket. 

c. Examine switch for poor contact or broken blades. 

d. Examine each part of circuit, switches, line, and sockets with magneto, 
which will locate opening. The wire may be broken at ground or trolley 
connections. 

Brakes fail to Operate: 

In great emergency only, throw controller handle to off, reverse reversing- 
switch, and turn controller handle to first or second notch. 
In sliding down grades, or when there is time, proceed as follows : 

a. Throw controller handle to off point. 

b. Throw canopy switch off. 

c. Reverse reversing-switch. 

d. Throw controller handle around to last notch. Both methods are 
more or less strain on the motors, but the second is somewhat less so than 
the first. 

4* round* : Either on field or armature coils will nearly always blow 
fuse ; it can then be tested out. 

Sucking': When running along smoothly, a car will sometimes com- 
mence jerky, bucking motions, and should be thoroughly examined at once. 
It may be due to a ground of field or armature that may short-circuit one or 
the other, either fully or intermittently. Injured motor may usually be 
located by smell of burning shellac, and can be cut out at the controller, 
and the car run in with the good motor. 

Mud and water splashing on commutator will sometimes produce bucking, 
and often a piece of wire caught up from the track may do the same. 

ELECTROL¥§I§ Of WATER AUTR OTHER 
PIPES. 

(From Report of the Electrical Bureau of the National Board of Fire Under- 
writers, on Electrolytic Deterioration of Water Pipes.) 

Recent reports show that the destructive effects of electrical currents on 
subterranean metal pipes are becoming sufficiently marked in many parts 
of the country to seriously interfere with the service the pipes are intended 
to perform. 

Underground water mains have broken down, because of faults unques- 
tionably due to electrolytic action ; and smaller service pipes have been 
weakened to such an extent as to break at critical moments, when excess 
pressure is put upon them at intervals during a fire. Measurements show 
that conditions imquestionably exist in nearly eveiy district in the United 
States covered by a trolley road, which are favorable for destructive action 



REPORT OF THE ELECTRICAL BUREAU. 525 



on the subterranean metal work in the vicinity, and pipes taken up in many 
of these districts show unmistakable signs of harmful effects. The general 
nature of this action, and the causes which bring it about, are too often 
seen to need elaborate description. Briefly it may be compared to the 
action which takes place in an electro-plating bath. 

The current which enters the bath through the nickel or silver metal sus- 
pended therein, flowing through the bath and out through the object to be 
plated, ultimately brings about the destruction of the suspended piece of 
metal. Similarly the current from a grounded trolley system flowing 
through the earth in its course from the cars back to the generating station 
selects the path of least resistance, which is generally for the whole or a 
part of the way the underground water mains, and at points where it leaves 
the pipes to reach the station the iron of the pipe wastes away until at 
points the walls become too thin to withstand the pressure of the water, 
and a breakdown ensues. The difference of potential necessary to bring 
about this action is very small, — a fraction of a volt, — and consequently 
in all districts where potential differences are found between water-pipes 
and the surrounding earth, such actions can be assumed to be taking place; 
for dampness, and the salts necessary to produce electrolysis, are present in 
all common soils. 

Whenever, then, a reading is shown by an ordinary portable voltmeter 
registering tenths of a volt with the positive binding-post in electrical con- 
nection with a water-pipe or hydrant, and the negative binding-post in elec- 
trical connection with an adjacent lamp post, car track, or metal rod driven 
in the earth, electrolytic action will be found upon examination to be tak- 
ing place at that point which will ultimately result in the destruction of the 
water-pipe. 

The only certain remedies for this evil are obviously to keep the current 
from using the pipes as a conductor, or to keep it from flowing from the 
pipes through the surrounding soil. The first remedy necessitates a com- 
plete metallic circuit for the railway, and the second a joining of pipes by 
wires wherever potential differences are found. Trolley roads having abso- 
lutely no ground connections will not be installed as long as the present 
trend of practice prevails, and consequently an absolutely complete metal- 
lic circuit for such roads cannot be secured. Bonding all underground 
pipes together with wires of sufficient carrying capacity to prevent current 
flow through the earth would also be obviously impossible. By a judicious 
employment of part of each remedy, however, it has been demonstrated 
that the evil can be so largely reduced as to be practically negligible ; and it 
is to securing these improvements in the numerous trolley districts of the 
country that the energies of everyone interested should be devoted. 

Referring to the diagram shoAvn in Fig. 82, it is seen that the current will 
pass from the generator out over the trolley line, through the motor to rail. 
Through rails and pipe the current flows back to the power-house. There 



r> _JL> 




I V |P4 



Fig. 82. 

are obviously two paths open for the current. One a return through the 
rail, the other a return through the earth and any existing gas-pipes, water- 
mains, or other metallic structures that may be in its path in the earth. The 
current flowing through these two paths in parallel is plainly inversely propor- 
tional to the resistance of these two paths. Therefore, in a general way the 
current will leave the rails at A, flowing into the water-pipe at B, and will 
again leave the water-p'pe at C and enter the rails. Here, then, is an elec- 
tric current flowing between metallic structures that may be called elec- 
trodes at places in the return path from the motor to station. All that 
remains, then, to promote electrolytic action is the presence of some solu- 
tion which will act as an electrolyte. 



526 



ELECTRIC STREET RAILWAYS. 



Observation lias shown that the earth, especially in the larger cities, con- 
tains a large percentage of metallic salts in solution, which will readily act 
as electrolytes upon the passage of electric current. It can be seen, then, 
referring to this diagram, that if there exists in the ground sufficient moist- 
ure of some metallic salt, electrolytic action will take place between the 
electrodes A and B, and between the electrodes C and the rails. The metals 
of this electrolyte will be deposited at B and on the rails, while the active 
part of the electrolyte will be found at A and C. Consequently, corrosion 
of the metallic structure may be expected at A and C, and at all points 
where current is found leaving the metallic structure. Such conditions as 
are shown in Fig. 82 exist in practically all of the railroads in this country. 
The rail and feeder returns offer one path for the flow of current ; and as the 
earth with its water-pipes and gas-pipes offers a parallel path, the amount 
of current flowing through the earth will then depend upon the resistance 
of the return path in the track and feeders. If, at a point in the track re- 
turn there exists a joint of somewhat high resistance, this high resistance 
Avill tend to prevent the current flowing back through the rails. The other 
return path of the current offered is through the earth and water-pipe. 
Consequently, electrolytic action in any metallic structure which may occur 
in the earth path of the return current is practically almost directly propor- 
tional to the faultiness of the construction in the rail return. In the earlier 
electric roads the positive terminals of the generators were connected to 
ground. This arrangement of the polarity of the street railway has a 
tendency to distribute the points of danger on water-pipes, gas-pipes, cable- 
sheathing, or any other underground metallic structure throughout a large 
and extended territory. By reversing the polarity of the railway generator, 
bringing the positive terminal to line and negative to ground, the points 
where the current leaves these metallic structures will be brought much 
nearer the power station, and will be localized in a much smaller area. At 
the same time that these danger points or points of positive potential are 
brought closely to the power station, it can be seen that the volume of cur- 
rent flowing from these danger points has been proportionally increased, and 
with it the amount of electrolytic action or corrosion. 




Fig. 83. 

On the Avhole, the placing of the current positive to line appears to be a 
material advantage. Corrosive action is very much enhanced in a limited 
area, but being in a limited area and definitely located, it may be easily 
watched and remedies applied. With the current negative to line, the ac- 
tion at a given danger point may be considerably less than under the other 
condition ; but as the danger district is widespread, and as the conditions are 
continually changing, it would be very difficult to locate precisely the dan- 
ger points. Consequently the results of electrolytic action are likely to ap- 
pear at unexpected points. 




Fig. 84. 



REPORT OF THE ELECTRICAL BUREAU. 



527 



From the electric railway standpoint, the prohibitive expense of the 
requisite addition of copper to make a complete circuit is advanced, to- 
gether with the impracticability of a double-trolley system that is appar- 
ently a necessary concomitant of the metallic return ; and these arguments 
have a certain weight. There is no question but that the complete metallic 
return is in the beginning a more expensive installation, but per contra few 
railway companies have any idea of the energy now expended in returning 
the energy delivered by the power station through the poor conductivity of 
the average railway track with its surrounding earth. 

It has been suggested that corrosion from the underground current could 
be avoided by operating the railway as a three-wire system in which the 
trolley wires would form the two sides, and the ground play the part of a 
neutral wire. The feasibility of a three-wire system depends upon the abil- 
ity to obtain a double track through the entire railway territory, and the 
adoption of such a car schedule as to render the loading of the two sides of 
the system essentially equal. Such a railway could rarely be successfully 
operated excepting in cities that are essentially level, and in which the 
traffic was exceedingly uniform. The probability is that in practice elec- 
trolytic action would not be wholly avoided ; and due to inequality in car 
loading and car scheduling it would be impossible to locate the danger 
points in the system, and therefore impracticable to employ methods of 
correction. 

Harold P. Brown has proposed an arrangement which is diagrammati- 
cally outlined in Fig. 85. At the station at least two or more generators are 
required, the division of units being such that there is at least one special 
generator of about one-quarter the total capacity of the station, which is to 
be connected, as indicated in the diagram, directly to the pipe structures in 



5l0|b 



□□□□ 



n 



TJ 



J 




Fig. 85. 



the street. The remainder of the station generators are, as usual, connected 
to the rails or to the return feeds. If, now, the special machine be operated 
at a few volts higher potential than the rest of the station, it is quite evi- 
dent that its action will be to render the pipe structures to which the nega- 
tive pole of the special generator is connected electro-negative to the rest 
of the system, thus obviating electrolytic action. Such an arrangement of 
station machinery is undoubtedly a palliative. It is by no means a cure, 
for in case in any part of the pipe system there happens to be a high resist- 
ance joint, such a joint would become a point of inflection in the current, 
being electro-positive on one side and electro-negative on the other side. 
It is, perhaps, possible to locate such joints by means of a careful voltmeter 
survey, but only at the expense of considerable time and trouble ; and when 
dangerous spots of this kind are determined, the resistance of the joint must 
be obviated either by some form of bond or other device. It will be readily- 
perceived that in many instances pipe structures will not return near 
enough to the station to render such an action as is outlined in the diagram 
possible, and frequently the pipe lines may be parallel to the railway track 
for a considerable distance, and then lead away from the station in such a 
way as to render the application of this method impractical. Under these 
circumstances it will be necessary to determine by means of a voltmeter 



528 ELECTRIC STREET RAILWAYS. 

survey the condition of the underground structures, and run to the danger 
points a special conductor. 

Very recently Mr. Farnham has proposed an additional solution of the 
electrolytic problem, which appears to be one of considerable merit. The 
usual conditions, together with the remedy proposed, are outlined in Figs. 
82 and 86. Under ordinary circumstances, the railway system is operated 
as shown in Fig. 82. 

The positive pole of the generator is connected to the trolley wire, and 
current passes from the station over the trolley wire, and then to the rails. 
From this point it returns to the station by the route of least resistance, 
whether through the ground, the rails, or a neighboring pipe line, as the 
case may be. At all points where the current leaves the pipe line or other 
underground structure, the line becomes electro-positive to its surround- 
ings and affords points of danger, as is indicated in the diagram. 

Suppose the circuit to be arranged as shown in Fig. 86. Here, as in the 



JOJ- 



JL 



pnnn 




- -t ~ss+ s^ : jz~sJt - sz zzz~+z zzzrz zzz. sz~:2zk:i* 

■t =-l B=£: 3 a (1=0 

Fig. 86. 

previous case, the positive pole of the generator is connected to the trolley 
wire, but the negative pole is not connected to ground in any way. On the 
contrary, the generating station is carefully insulated from earth, the nega- 
tive pole being connected to a set of return feeds that may be strung along 
the route of the railway on the same poles that carry the positive feeds. At 
frequent intervals, say at every pole, or every other pole, the return feed, 
which is otherwise carefully insulated, is connected to the rails only through 
sets of variable resistances, as indicated on the diagram. These resistances 
are proportioned in such a manner as to render all paths from and to the 
station of precisely the same resistance — that is to say, from the station 
the resistance of the circuit to the farthest car and back to the station will 
be the same as the resistance from the station to the nearest car and back 
to the station. 

A consideration of the diagram Avill render it quite evident that as the 
generators at the station are entirely insulated, and as the return feeds are 
connected at frequent intervals to the rails in such a manner as to render 
all the paths of equal resistance, no current will flow from the rails, except- 
ing such as passes from any car to the two nearest points of return to the 
return feeds ; and under these circumstances there is little or no tendency 
for the current to leave the rails and pass to any adjacent underground 
structures. It is, of course, conceivable that a pipe line may be so near 
the rails — within a few inches of them, perhaps — that a slight amount 
of electricity may escape to the pipe line for a few feet. Such cases would 
have to be particularly guarded, but would form an exceedingly infrequent 
exception to the general rule. 

The objection to be urged against this expedient will inevitably be the 
additional expense required in the erection and maintenance of the return 
feeds, for this expedient amounts to giving the railway a complete metallic 
circuit ; only using the rails to carry current between the adjacent poles. 

I. II. Fiiinnin in a paper before the A.I.E.E. gives the follow- 
ing conclusion, viz., 

First — All single-trolley railways employing the rails as a portion of the 
circuit cause electrolytic action, and consequent corrosion of pipes in their 
immediate vicinity, unless special provision is made to prevent it. 

Second— A fraction of a volt difference of potential between pipes and 
the damp earth surrounding them is sufficient to induce the action. 

Third — Bonding of rails or providing a metallic return conductor equal 
in sectional area and conductivity to the outgoing wires is insufficient to 
wholly prevent damage to pipes. 



THIRD-RAIL SYSTEM. 



529 



Fourth — Insulating pipes sufficiently to prevent the trouble is imprac- 
ticable. 

Fifth — Breaking the metallic continuity of pipes at sufficiently frequent 
intervals is impracticable. 

Sixth — It is advisable to connect the positive pole of the dynamo to the 
trolley lines. 

Seventh — A large conductor extending from the grounded side of the 
dynamo entirely through the danger territory, and connected at every few 
hundred feet to such pipes as are in danger, will usually insure their pro- 
tection. 

Eighth — It is better to use a separate conductor for each set of pipes to 
be protected. 

Ninth — Connection only at the power station to water or gas pipes will 
not insure their safety. 

Tenth — Connection between the pipes and rail, or rail return wires out- 
side of the danger district, should be carefully avoided. 

Eleventh — Frequent voltage measurements between pipes and earth 
should be obtained, and such changes in return conductors made as the 
measurements indicate. 



VHI1ID.B1U SYSTEMS. 





FiG. 87. Trolley, Metropolitan West Side 
Elevated Railway, Chicago, 1895. 



The use of an insulated rail 
alongside of or between the rails 
of the regular track, for carrying 
the current for the motors, was 
one of the earliest forms used for 
electric railroads ; but until its 
use on the Intramural Railway 
at the World's Fair, Chicago, in 
1898, demonstrated its success 
and reliability when well laid 
down, there had been so many 
defects in the construction, and 
faults from its use, that the over- 
head trolley wire was substan- 
tially the only method given any 
attention. The complete success 
of the system as laid down at 
the Fair resulted in the installa- 
tion of the third or conducting 
rail on three of the Chicago 
elevated railways during the 
years 1895-1896 ; and being con- 
structed in a rational and me- 
chanical manner, the success 
has been complete and continu- 
ous. 

The Metropolitan West Side 
Elevated Railway started the 
use of the third rail in 1895. 
This rail is of steel T, supported 
upon wooden blocks placed at 
one side of the tracks, and the 
current is collected from this 



rail by four iron brushes suspended from each car. 

The Lake Street Elevated Railway laid down a third-rail system in 1S96. 
This rail is supported upon pillar insulators six feet apart, and is protected 
by wooden guard rails. 

The Northwestern Elevated Railway started its use of a third-rail system 
in 1896. 

All the above-named roads make use of the track and structure for return 
circuit, and the electrical pressure used is abotit 500 volts. 



530 



ELECTRIC STREET RAILWAYS. 



I 




Elec. World Engineer. 
Fig. 88. Diagrams of Truck, Showing Shoe-Lifting Mechanism. 



, 



CONDUIT SYSTEMS OF ELECTRIC RAILWAYS. 531 



In Fig. 88 is shown a very good form of attachment for third-rail contact- 
shoe, as used on the Albany and Hudson Railway and Power Company line. 
This shoe can be turned up out of the way when entering city streets, and 
the regular overhead trolley that is hooked down on the top of the car 
while on the private right-of-way, can be used. 

In the East, perhaps the best-known example of tbe use of the third rail 
is that of the Nantasket branch of the New York, New Haven, and Hart- 
ford Railroad, which was equipped in 1896. The voltage used is 500. 




FIG. 89. Section of Third Rail at Joint, Nantasket 
Branch N. Y., N. H., & H. R. R., 1896. 



The rail section used is inverted V in form, weighs 93 pounds per yard, 
and is supported without fastening on wooden blocks tenoned into the 
ties. There is a contact shoe weighing 25 lbs. hanging loosely from the 
motor trucks at either end of the cars, and making contact by its weight. 
As there is a break in the conducting rail at all crossings and turnouts, the 
shoe at the front end always makes contact before the rear shoe leaves the 
last rail. 

As the conducting rail is but five-eighths inch above the ties and earth 
lightning jumps to ground freely ; and experience shows that the distance of 
this rail above the ground is scarcely wide enough, as the power current 
also frequently jumps over. 

Where the third rail breaks at crossings, etc., the ends are connected by 
well-insulated cable laid in wooden duct underground. Sloped wooden ap- 
proaches are placed at the ends of the third rail at these breaks in order 
that the contact shoe may ride up onto the rail easily. 

The third-rail system as used on the above-named railroad is said to be 
inexpensive of construction and quickly laid. There is little wear and tear 
on the rail or contact shoe, and large amounts of current can be collected 
without danger. 

Other examples of the use of the third rail are the New Britain and Hart- 
ford, Conn., branch of the N. Y. & N. H. Railroad, the New York and 
Brooklyn Bridge, and the Brooklyn Elevated Railways. 



coafDriT systems or electbic raiiway§. 



Previous to 1893 hundreds of patents were granted on conduit and other 
sub-surface systems of carrying the conductors for electric railways, and 
hundreds of experiments were carried on ; but it has been only since that 
year that capitalists have had the necessary courage to expend enough 
money to make a really successfully operating road. The work was put 
into the hands of competent mechanical engineers, who perfected and im- 
proved the mechanical details, and the electrical part of the problem was 
by that means rendered very simple. 



532 ELECTRIC STREET RAILWAYS. 



The Metropolitan Street Railway Company of New York, and the Metro- 
politan Railroad Company of Washington, decided, in 1894, that, hy build- 
ing a conduit more nearly approaching cable construction, the underground 
electric system could be made a success. The former contracted for its 
Lenox Avenue line, and the latter for its Ninth Street line. The New York 
road was in operation by June, 1895; the Washington road by August of 
the same year ; and they continue to run successfully. While modifications 
have been made in some details since these roads were started, yet the 
present construction is substantially the same. These roads were the first 
to avoid the almost universal mistake of spending too little and building 
unsubstantially where new enterprises are undertaken. The history, in 
these particulars, of the development of overhead trolley and conduit roads 
is to-day repeating itself in the third-rail equipment of branch and local 
steam roads. 

The Metropolitan Railroad, in Washington, used yokes of cast iron placed 
on concrete foundations, and carrying the track and slot rails. The slot 
rails had deep inner flanges, with water lips to prevent dripping on con- 
ductors. The conductor rails were T bars 4 inches deep, 13 feet 6 inches 
long, 6 inches apart, and were suspended from double porcelain corrugated 
insulators filled with lead and mounted on cast-iron handholes. A sliding 
plow of soft cast iron collected the current. During the first few months of 
its operation there were but few delays, mostly due to causes other than 
electrical defects. Some trouble came from short-circuiting of plows, which 
was remedied by fuses on plow leads, and a water rheostat at the power- 
house. The flooding of conduits did not stop the road, although the 
leakage was 300 to 550 amperes. Under such circumstances the voltage was 
reduced from 500 to about 300. The average leakage on minus side, when 
tested with plus side grounded, was one ampere over 6,500 insulators. The 
positive side always showed higher insulation than the negative, possibly 
due to electrolytic action causing deposits on the negative pole. 

The Lenox Avenue line of th j Metropolitan Street Railway was the first 
permanently successful underground conduit line in the United States. 
The cast-iron yokes were similar to those used on their cable lines, placed 
5 feet apart. Manholes were 30 feet apart, with soapstone and sulphur ped- 
estal insulators located under each, carrying channel beam conductors, 
making a metallic circuit. At first the voltage'was 350, hut it was gradually 
raised to 500. The pedestal support was afterwards abandoned, and sus- 
pended insulators used every 15 feet, at handholes. At one time iron-tube 
contact conductors were tried, hut they proved unsatisfactory. 

The details of track construction for underground or sub-surface trolley 
railroads are essentially of a special nature, and are determined in every 
case by the local conditions and requirements. They belong to the civil en- 
gineering class entirely, and will not he treated here in any way other than 
to show cuts of the yokes and general construction. 

The requirements of the conduit for sub-surface trolley conductors are 
first, that it shall be perfectly drained, and second, that it be so designed 
that the metallic conductors are out of reach from the surface, of any- 
thing but the plow and its contacts. Another requisite is that the conduct- 
ing rails and their insulated supports shall be strong and easily reached for 
repairs or improvement of insulation. 

The conducting rails must be secured to their insulating supports in such 
a manner as to provide for expansion and contraction. This can be done by 
fastening the center of each section of bar solid to an insulated support at 
that point, and then slotting the ends of the bar where they are supported 
on insulators. The ends of the bars will be bonded in a manner somewhat 
similar to the ordinary rail bonding. 

The trolley circuit of the sub-surface railway differs from the ordinary 
overhead trolley system in that while the latter has a single insulated con- 
ductor, and return is made by the regular running rails, the former has a 
complete metallic circuit, local, and disconnected in every way from track 
return. 

The contact rails must be treated like a double-trolley wire, and calculations 
for feeders and feeding in points can be made after the methods explained 
for overhead circuits and feeders earlier in this chapter. Feeders and mains 
are usually laid in underground conduits for this work, and the contact rails 
may be kept continuous or may be divided into as many sections as the ser- 
vice may demand, taps from the mains or feeders being'made to the contact 



COXDUIT SYSTEMS OF ELECTRIC RAILWAYS. 



533 





534 



ELECTRIC STREET RAILWAYS. 




Fig. 92. Drainage at Manhole of Conduit, Metropolitan Railroad, 
Washington, 1895. 



Mr* 



XU 



.Mm, j- 






! . 1 ^ 6 : : 






7 " " 


— i — f — (- 


I ; I !: ' i ji 









— 54i ,j 

D ELEVATION OF CLIP 



k--2Vr--1 




PLAN OF CLIP 

Fig. 93. Clip and Ear for Conduit, Metropolitan Railroad, Washington, 

1895. 



rails at such points as may he determined as necessary. All the insulated 
conductors should be of the highest class ; may be insulated with rubber or 
paper, but should in any case be covered with lead. Especial care should 
be taken in making joints between the conducting rail and copper conductor 
so that jarring will not disturb the contact. 

Other than the above few general facts it is difficult to say much regard- 
ing this type of electric railway, for it is so expensive to install that it can 
be used in but a few of the largest cities, and in every case will be special, 
and require special study to determine and meet the local conditions. The 
reader is referred to the files of the street railway journals for complete 
descriptions of the few installations of this type of electric railway. 



CONDUIT SYSTEMS OF ELECTRIC RAILWAYS. 



535 



Follcrwing are a number of cuts showing the standard construction of 
electric conduits as designed and built by the Metropolitan Street Railway 
Company, of New York. The system of railway may be said to use all the 
latest methods, including wire-carrying conduits along side or under the 
tracks, as will be seen by the next cut. 

The porcelain insulator here shown for supporting the contact rails is 
very substantial in design and construction, and by its location at a hand- 
hole is easily reached for cleaning, repairs, and replacement. The plow has 
also received careful attention, and those now used as standard by the Met- 
ropolitan Company leave little to be desired. 



p — 1—6 + 1-6— A 




Fig. 94. Section of Conduit, Metropolitan Street Railway, New York. 
Standard Work, 1897-98. 




Fig. 95. 



Section, Side and End Elevation of Plow, Metropolitan Street 
Railway, New York. — Standard Work, 1897-99. 



536 



ELECTRIC STREET RAILWAYS. 




TOP OF TRAM. RAIL 



Fig. 96. Plan and Elevation of Plow Suspension 
from Truck, Metropolitan Street Railway, New 
York. — Standard Work, 1897-98. 




Fig. 97. Section and Elevation of Insulator, Metropolitan Street Railway, 
New York. — Standard Work, 1897-98. 

SURFACE COKfTACT OH ELECTBO-MACrlVETIC 

The development of surface contact systems began even earlier than j&ss 
use of the overhead-trolley wire, and many patents have been issued on the? 



WESTINGHOUSE SYSTEM. 537 

same. Most of these failed through ignorance of the requirements, and 
timidity of capital in taking up a new device answers for others. 

The Westinghouse Electric and Manufacturing Company and the General 
Electric Company finally took the matter up, and being equipped with vast 
experience of the requirements, and the necessary engineering talent and 
apparatus, have each developed a system that is simple to a degree, and is 
said to cost but half as much to install as the conduit system, and to offer 
advantages not known to that or other systems. 

I quote as follows from a bulletin issued by the Westinghouse Electric 
and Manufacturing Company. 

Some Advantages of the System. 

No poles, overhead wires, or troublesome switches are employed. The 
streets, yards, and buildings are left free of all obstructions. 

The facility with which freight cars can be drilled in yards and through 
buildings, without turning the trolley whenever the direction of a motor 
car or locomotive is reversed, and the absence of the necessity of guiding 
the trolley through the multiplicity of switches usually found in factory 
yards and buildings, is of great advantage, permitting, in fact, the use of 
electric locomotives where otherwise electricity could not be used. 

The only visible parts of the system, when installed for street railway 
work, are a row of switch boxes between the tracks, flush with the pave- 
ment, and a double row of small contact buttons which project slightly 
above the pavement, and do not impede traffic in any way. 

This system can be used in cities where the use of the overhead trolley is 
not permitted, and if desired the continuation of the road in the suburbs 
can be operated by the cheaper overhead system. It would only be neces- 
sary to have a trolley base and pole mounted on the car, the pole being 
kept down when not in use. 

There are no deep excavations to make. The system can be installed on 
any road already in operation without tearing up the ties. 

The cost is only about one-half that of a cable or open conduit road. 

The insulation of all parts of the line, the switches, and the contact but- 
tons is such that the possibility of grounds and short circuits is reduced to a 
minimum. 

The system is easy to install, simple in operation, and reliable under all 
conditions of track and climate. 

Finally, the system is absolutely safe. It is impossible for anyone on the 
street to receive a shock, as all the contact buttons are " dead " except- 
ing those directly underneath the car. 

Requirements. 

In devising this system the following requirements of successful working 
were carefully considered. 

The insulation must be sufficient to prevent any abnormal leakage of 
current. 

The means for supplying the current to the car must be infallible. 

The apparatus must be simple, so that inexperienced men may operate it 
without difficulty. 

The system must operate under various climatic conditions. 

Finally, absolute safety must be assured. 

WESTUVGHOUSE iTSHM. 

This system includes the following elements. 

First. Electro-magnetic switches, inclosed in moisture-proof iron cases. 
Each switch is permanently connected to the positive main or feeder which 
is laid parallel to the track. 

Second. Cast-iron contact plates or buttons, two in each group, placed 
between the rails and electrically connected to the switches. A separate 
switch is provided for each group of buttons. 

Third. The conductor forming the positive main or feeder. This is com- 
pletely inclosed in wrought-iron pipe, and is connected to the various 
switches. 



538 



ELECTRIC STREET RAILWAYS. 



Fourth. Metal contact shoes or bars, suspended from the car trucks ; 
two bars on each car. 

Fifth. A small storage battery carried upon the car. 

The operation of the system is described as follows, and is illustrated by 
cuts making plain the text. 




Fig. 



Diagram of Switch Connections. 



CONTROLLER 

HVWW 




Dj^. STORAGE BATTERY* 
R PICK UP BAR 



Qi 

CONTACT-BARS- Q 



COLLECTOR BAR 



Fig. 99. Diagram of Car Connections. 



Electro-magnetic switches, X 1? X 2 , X 3 ., inclosed in water-tight casings, 
are installed at intervals of about 15 feet along the track to be operated. 
Each switch is provided with two windings, I and H, which are connected 
by the wires N and M to two cast-iron contact buttons, 1 and 2, which are 
mounted, on suitable insulators and placed between the rails. 

Each car to be operated on this system is provided with two spring- 
mounted T steel contact bars, Qj and Q 2 , and a few cells of storage battery 
in addition to the usual controllers and motors. The contact bars are 
mounted at the same distance apart as the contact pins, 1 and 2, so that as 
the cars advance along the track the bars will always be in contact with at 
least one pair, as the length of the bar exceeds the distance between any 
two pairs by several feet. 

Suppose a car is standing on the track over the switch X 2 , the contact 
bars, Qx and Q 2 , being then in connection with the buttons I and 2 respec- 
tively. The first step is to "pickup" the current, i.e., render the buttons 
1 and 2 alive. 

Switch A is first closed ; this completes the circuit from the storage bat- 
tery, D, through the wiring, R, contact shoe, Q,, button No. 1, and shunt 
coil, H, to the ground. The current passing through H magnetizes the 
core, S, which in turn attracts the armature, P, closing the switch and es- 
tablishing connection between the 500-V main feeder K, and button No. 2, 
through the contacts, J J, coil I, and wiring N. Switch C is now closed and 
switch A opened ; the switch X 2 is kept closed, however, by the current 
flowing from button No. 2 through bar Q,, connection T, resistance L, con- 
nection R, bar Q,, button No. 1, connection M, coil H to ground. 

The car now proceeds on its way, current from the main passing through 
connection T, to the controller and motors. When the car has advanced a 
short distance the contact bars make connection with the pair of buttons 
connected to switch X 8 . Current then passes from bar Q, through the 
shunt coil of this switch. The operation described above is then repeated. 
As soon as the bars leave the buttons 1 and 2, current ceases to pass through 
the coils I and H of switch X 2 , and this switch immediately opens by grav- 



WESTINGHOUSE SYSTEM. 



539 



ity, leaving the buttons connected to it dead and harmless. As connection 
with the main has already been established through switch X 3 , there will 
be a continuous flow of current from the feeder, and no flash will occur 
either at the button or the switch. 

It will be observed that all the current passing to the car from the main 
through switch contacts J J passes through the series coil, I, holding the 
switch firmly closed and precluding all possibility of its opening while cur- 
rent is passing through the contacts, even should the circuit through coil H 
be interrupted. Although the act of "picking up the current" requires 
some time to describe, it takes in practice only a few seconds. 

Two separate switches, A and C, are shown in the diagram; but in practice 
one special switch of circular form is provided, and the necessary combina- 
tions required for " picking up the current " are made by one revolution of 
the switch handle. 

The battery need only be employed to lift the first switch; for after that 
has been closed, the contact shoes bridge the main voltage over from one set 
of pins to another, as described, thus closing the successive switches, with- 
out further attention from the motorman. 

The battery is charged by leaving switches A and C closed at the same 
time. 

Tlie Switch. 

Fig. 100 shows the general arrangement of switch, bell, and pan. The 
switch and magnet are mounted upon a marble slab, which is secured in 
the bell by means of screws to the bosses, B B. 

The switch magnet, M, is of the iron-clad type. It is secured to the upper 




Fig 100. Section of Switch, Bell, and Pan. 

side of the marble base, and is provided with a fine (shunt) winding for the 
" pick up " current, and a coarse (series) winding through which the work- 
ing current passes. 

When magnetized the poles attract an armature attached to a bridge piece, 
J, each end of which carries a carbon disk, N. R, R, are guides for the bridge 
piece, J. Directly above each of the carbon disks, N, is a stationary disk, 
O, mounted upon a marble base. One of the disks, O, is permanently con- 
nected by means of one of the contact cups, G x , as explained later, to the 
positive main cable, and the other, through the series coil and cup, G 2 , to 
the positive contact button. 



540 



ELECTRIC STREET RAILWAYS. 



The pan, C, is provided with four bosses, S, to support the vertical split 
pins, F, which are insulated from the pan. These pins slide into recepta- 
cles, G, on the switch base. The pins, F, are provided with connectors, I, 
for the purpose of making connection with the several cables, H, which pass 
through the holes in the under side of the pan. The pan is completely filled 
with paraffine after the connections are made, thus effectually keeping out 
all moisture. 

The object of the bell, A, and the pan, C, with the split pins, F, and the 
cups, G, is to provide a ready means of examination of the switch without 
disconnecting the wires. The bell can be lifted entirely free of the pan. 
In replacing it, it is only necessary to see that a lug, T, on the side of the 
cover, fits into a slide, U, on the frame. When in this position the split 
pins make connections with their corresponding cups, G. 

The bell, A, is provided with lugs, L, to facilitate handling ; and also a 
double lip, W. The inner portion of this lip fits into and over the annular 
groove, D, of pan C. This groove is filled with a heavy non-vaporizing oil. 
The outer portion of lip, W, prevents water from entering the groove. The 
object of the groove, D, and the lip, W, is to make a waterproof joint to pro- 
tect the switch and cable terminals without the necessity of screw joints or 
gaskets. The bells are all tested with 25 pounds air pressure ; they may be 
entirely submerged in several feet of water without affecting the operation 
of the system. 

The Contact Buttons are made of cast iron. They are about 4^ inches 
in diameter, and, when installed on paved streets, project about five-eighths 
of an inch above the pavement and offer no obstruction to traffic. This is 
sufficiently high to enable the collector-bars to make contact, and at the 
same time to entirely clear the pavement. For open-track installations they 
are substantially mounted in a combination unit as described below. 




Fig. 101. Section of Combination Unit. 



The Combination Units. 

The bell and pan are entirely inclosed in a cast-iron switch-box. This box 
and the contact buttons are made into a complete unit as shown in Fig. 101. 
Each unit consists of three separate castings. The cylindrical cast-iron 
box, which incloses the switch, bell, and pan, is bolted into a recess provided 
for that purpose in the bottom of the spider-like structure, A\diich is a sep- 
arate casting, consisting of box rim, receptacles for the button insulators, 
and supporting arms. The removable lid is the third casting. 

The insulators, A, Fig. 101, are made of a special composition, and are ce- 
mented into the tapered cups, B, and supported by the iron plates, C. The 
contact buttons, E, are mounted on top of these insulators and stand, when 
installed, about one inch above the rail. 

The four arms, G, are secured to the ties by means of the bosses, H, thus 
reducing to a minimum the labor of leveling the boxes and avoiding the 
necessity of special ties. 



WESTINGHOtJSE SYSTEM. 



541 



Mains and Wiring-. 

The positive main or feeder is incased in a lj-inch iron pipe, and passes 
directly through each switch-box, and a tap is made to each switch, the 
switch-boxes being all connected by the iron pipe, as per cut below. 




Track Equipped for Track Return Circuit. 



No additional wires are used to interconnect the coils or contacts of ad- 
jacent switches. 

The Contact Bars are of steel, of ordinary T section. They are sup- 
ported from the car trucks by two flat steel springs and adjustable links. 
These bars are inclined at the ends so that they may readily slide over the 
buttons and over any ordinary obstacle. 

Insulated Return I<ine. 

In case it is considered best not to use the rails as the return line, insu- 
lated mains for this purpose may be included in the system. It is only 
nacessary to install another row of contact buttons, another collecting bar, 




FlG. 103. Track Equipped for Insulated Return Circuit. 

and to use double-pole switches. Fig. 103 illustrates an installation of this 
kind. For all ordinary work, however, the ground return is satisfactory. 



Modifications of the System. 

The description given on the preceding pages applies to the system as in- 
stalled for yard and similar work. Modifications can be made and detail 
matters arranged according to the requirements of each case. 

Street Railway Work. 

The foregoing description applies to installations where the track is open 
(unpaved),and where it is unnecessary to make provision for traffic crossing 
the tracks except at certain points. For street railway work, the switch- 
boxes are preferable installed outside the track, while the buttons are 
placed between the rails and mounted on a light metal tie, as shown in Fig. 
104. 



542 



ELECTRIC STREET RAILWAYS^ 



The operation of the system is exactly the same as in open-track work. 
Connecting wires pass from the buttons under the tie to the switch-boxes. 
For double-track work the switches are installed between the two tracks, 
and the boxes may he built to hold two switches, one for each track. 



UN£_orj?AviN<S 




CHANNEL IRON 



Fig. 104. Section of Track Equipped for Street Railway Service. 

"When, as is sometimes necessary, the buttons are placed in a single row,, 
it is necessary that the "pick-up" current should be of the same voltage 
as that of the main circuit, and consequently the car-wiring indicated in 
Fig. 105 is used, instead of that shown in Fig. 99. 



G MOTOR GENERATOR 



CONTROLLER 




,*1 



CONTACT BAR 



= STORAGE BATTERY 

D 

T 



Fig. 105. Diagram of Car- Wiring. 

Referring to Fig. 105, the method of "picking up" the current is as fol- 
lows : Switch A is first closed ; this completes the circuit from a storage 
battery D, through a small 500-volt motor-generator F, which immediately 
starts. As soon as it is up to speed, which only requires a few seconds, 
switch B is closed ; current then passes from F through the wiring R, to 
contact shoe Q, and then through the switch magnet, as explained on page 
538. Switches A and B are then opened, thus stopping the motor-generator, 
which need only be used to operate the first switch. The successive 
switches are closed, as described on page 538. 

This arrangement of a high-voltage " pick-up " may also be used advan- 
tageously with two rows of buttons where the track is liable to be obstructed 
by mud or snow. 

Sectional Rail Construction. 



For suburban railway or similar service two light rails may be substituted 
for the two rows of contact buttons, as shown in Fig. 106. The cars are 
then equipped with contact shoes instead of bars. These rails are insulated 
from the ground, and may also be insulated from each other wherever 
desirable, thus breaking them up into sections, which are each controlled by 
a single switch. The sections may be made of any desired length to suit the 
conditions. For example, between stations they may be 500 or more feet 
long, while near stations or crossings, where anyone is liable to come in 
contact with the rail, the length of a section may be reduced to 50 feet or 
less. The electrical operation of two-rail installations is the same as when 
two rows of buttons are used. The sectional switches along the tracks are 
entirely under the control of the motorman. and the rails may be rendered 
" dead" at any moment should occasion arise. 



GENERAL ELECTRIC COMPANY. 



543 



The Westinghouse Company uses a system of surface contact all over its 
large -works at East Pittsburg, and another plant has been in operation for 
.some time at Indian Head, Md. 




Fig. 106. Sectional Rail Installation. 



GENERAL ELECTRIC ST§TEM OE SURFACE 
COUTACT RAILWAY. 

Following is a description of the surface contact system, as developed by 
"the General Elective Company, and practical application of it has been 
made at Monte Carlo, and at the company's works at Schenectady. The 
description is from a report made by "W. B. Potter, Cf . Eng. of the Railway 
Department, and written by Mr. S. B. Stewart, Jr. 

In the operation of electric cars, by tbe closed conduit surface plate con- 
tact system of the General Electric Company, the current is collected for 
the motor service by means of tw r o light steel shoes carried under the car, 
making contact with a series of metal plates, introduced along the track 
between the rails, automatically and alternately energized or de-energized 
by means of switches grouped at convenient places along the line ; the 
method of the switch control being such that in the passage of the car, in 
either direction, it is impossible for any plate to become alive except when 
directly under the car body. 

In ordinary street car practice, the contact plates are spaced approxi- 
mately ten feet apart, positive and negative plates being staggered, as 
shown in Fig. 107, which admits of but three plates ever being covered at any 
one time by the shoes, which are so designed as not to span more than two 
plates of the same polarity. 

In grouping the switches it is customary to locate them either in vaults 
constructed between or near the tracks, or in accessible places along the 
side of the street, the location and spacing of groups and number of 
switches in each group being based upon a comparative cost between the 
style of vault or other receptacle, and the amount of wire with ducts be- 
tween the contact plates and their corresponding switches. 

The main generator feeder is carried to each vault or group, and auxiliary 
f ee>iers from it are distributed to each switch, the track rail being utilized 
for the return circuit. 



544 



ELECTRIC STREET RAILWAYS. 



The operation or performance of this system can be readily traced out by 
reference to -big. 10V. It will be seen that the current in its passage to the 
motor from the positive generator conductor passes to contact A of switch 
No. 2 through the carbons on its magnet armature (which has been lifted 
by the energized coil G) to contact plates B and C, through the contact shoe 
D to the controller and motor, coming out at contact shoe E to the contact 
plate F, when it passes through the coil of the automatic switch G, ener- 
gizing it and returning by the track-rail H ; thus maintaining contact at 
switch No. 2 armature carbons as long as the shoes remain on the contact 
plates C and F. It should now be noted that contact plate B is energized 



MOTOR <£ /^^k 





Fig. 



107. Diagram of Connections for Surface Contact Railway Plate 
System, General Electric Co. 



as stated above. As the car proceeds, the shoe D spans the plates B and Cr 
thereby keeping the coil of switch No. 2 energized after shoe has left plate 
C, and until shoe E comes in contact with plate J, which immediately ener- 
gizes coil No. 1, thus making the preceding contact plate energized, prepara- 
tory to the further advance of the car. It will be noted in the above 
description of the performance of the system, that we have assumed switch 
No. 2 on Fig. 107 as closed; it should therefore be understood that an aux- 
iliary battery circuit is necessary in starting or raising a first switch, pre- 
paratory to its armature being held in contact position by the generator 
current, which current energizes the preceding contact plates consecutively 
as described above. 

The battery current is brought into the automatic switch circuit momen- 
tarily during the period of first movement of handle of the controller in 
starting a car, the transition of the controller cylinder also bringing the 
generator current in connection with the battery for a short period of time, 
thus replenishing the elements sufficiently to operate the switches. The 
battery is also used to supply current for lighting the car, the generator 
circuit being disconnected while the car is at rest. 

Surface Contact JPlates. 

The surface contact plates are made of cast iron, with wearing surfaces 
well chilled, designed to be leaded into cast-iron seats in such a manner 
that they are thoroughly secure, but can be readily removed by special 
tongs for the purpose. The seat is imbedded in a wooden or composition 
block set into a cast-iron box, the latter being spiked or screwed to the tie. 
A brass terminal is fastened to the seat for the reception of the connecting 
wire from the switch. See Fig. 108. 



GENERAL ELECTRIC COMPANY. 



545 



As stated above, the plates are usually located 10 feet apart for straight 
line work, but somewhat closer on curves, depending upon the radius of the 
curve and length of contact shoe. The negative and positive contact plates 
are staggered with a uniform angular distance between them, situated not 
less than 10 inches from the track rails. 




Fig. 108. Plan and Section of Track, Monte Carlo, Europe. 
General Electric Company's Surface Contact System, 1898. 

Surface Contact Switch. 

The automatic switches are constructed on the solenoid principle, the 
armature or core of which is employed in closing the contacts as shown in 




Fig. 109. Automatic Switch for Open Conduit, Surface Plate Contact System. 



546 ELECTRIC STREET RAILWAYS. 



Fig. 109. The end of the armature core is provided with a pressed sheet- 
steel carbon-holder, for the purpose of supporting the carbon contacts which 
are held in place by bronze clips and cotter pins which can easily be re- 
moved. The pressed-steel carbon-holder can also be detached with little 
trouble by removing the end holding it to the core. Copper plates are se- 
cured to the slate base for contact surfaces and the attachment of feeder- 
wires. The wire of the solenoid is wound on a copper spool and placed in 
a bell-shaped magnet frame, and a pole-piece, slightly recessed to receive 
the end of the armature core when the switch is in a closed position, is at- 
tached to the top cover, and extends part way down through the winding. 
The recess in the armature increases the range of the magnet, making the 
attraction uniform except at the point of contact where the power increases 
rapidly, thus securing an- excellent contact. A blow-out magnet coil is con- 
nected in series with the feeder current, and so situated that the influence 
of its poles is used to rupture any arc that might be formed while the switch 
is opening ; however, this blow-out magnet is used simply as a precaution- 
ary device, as under ordinary conditions there is no arcing, the succeeding 
automatic switch closing the circuit before it is opened by the preceding one. 
Each vault or group of switches should be provided with cut-outs or an 
automatic circuit breaker to protect them in the event of short circuits. 

Surface Contact Shoes. 

The contact shoes are made of " T " steel of light section, the suspension 
for which is an iron channel beam extending longitudinally with the truck 
frame directly under the motors, with a substantial wooden cross-arm at- 
tached to each end for the shoe-supporting casting, the shoes being attached 
to these supporting castings by a spring equalizing device for maintaining 
the shoes at the proper height, and also for making them flexible enough to 
meet any slight variations in the contact plates and track rails. The shoes 
when in their correct position should never drop over one-fourth inch below 
the surface contact plates, and are designed so that they may raise three- 
fourths of an inch or more above them. See Fig. 110. 




Fig. 110. Collecting Shoes, Monte Carlo, Europe. 
General Electric Company's Surface Contact System, 1898. 

A screw adjustment is provided to lower the shoes as they wear away, or 
to take care of any other discrepancies due to Avear of parts, etc. ; if they 
are allowed to drop too low they will interfere with rail crossings, causing 
short circuits. 

Storage Batteries. 

It requires for closing the first automatic switch when starting, and for 
lighting the car approximately, ten storage battery elements capable of 35 
amperes rate of discharge for five hours. 



GENERAL ELECTRIC COMPANY. 547 



The batteries are only slightly exhausted in making the initial connec- 
tions through the automatic switch, as it only takes approximately 15 am- 
peres momentarily to perform this work, the battery is immediately 
recharged by current which has passed through the motors. The battery 
serving as a rheostatic step, this momentary charging does not represent 
any extra loss of energy. 

The circuit connections of the battery are accomplished in the controller, 
and require no attention on the part of the motorman. 

Car Iiigliting-. 

The amount of recharging derived from the motor circuits is sufficient to 
operate the automatic switches, but where lighting of the car is done from 
the same battery, an additional recharge is required. 

Assuming that 10 20-volt lamps are used for lighting a car, the batteries 
will need to be recharged every night about five hours, at an approximate 
rate of 25 amperes. 

It is customary to run leads from both the positive and negative terminals 
of the batteries to charging-sockets attached to the under side of one of 
the car sills in a convenient place for connection to the charging-wire. 

A small generator of low potential (30 volts) driven by a motor or other 
method is required for supplying current for recharging the batteries where 
the desired low-potential current is not accessible, and the wiring from the 
charging source should be run to a location in the car-house most convenient 
for connections to the battery sockets. These locations may be fixed either 
in the pits or on posts at the nearest point to where the cars will be sta- 
tioned, and there should be flexible lead wires attached to plugs for connect- 
ing to the battery circuit on the car. In wiring the car-house for the 
battery connections, it would be found convenient to designate the polarity 
of the various wires either by different colored insulation or tags, and the 
plugs at the ends of the flexible leads should be marked plus and minus to 
avoid mistakes in making connections with the car battery receptacle. 

Iflotors and Controllers. 

The motor and controller equipment used with the surface plate contact 
system is standard apparatus as ordinarily employed for electric car service, 
with the exception that provision is made in the controller for cutting in 
and out the storage battery while starting the car. 

Care of Apparatus. 

As success in the operation of the contact plate system depends largely 
on the care of the apparatus, a few general remarks on the subject will not 
be out of place here. 

Care should be taken that the contact plates are kept clean, and they 
should be frequently inspected, the roadbed being well drained. Any small 
quantity of water temporarily standing over the tracks, however, would do 
little harm, as the leakage through the water would not be sufficient to 
create a short circuit, although this condition should not be allowed to 
exist any length of time. 

The automatic switches should be carefully inspected and all cast-iron 
parts thoroughly coated with heavy insulating paint, and a test for insula- 
tion or grounds be made frequently, and all the parts kept clean and free 
from moisture. 

The contact shoes, in order to prevent leakage, should have their wooden 
supports well protected with a coating of an insulating paint, and should 
also be occasionally cleaned. 

The storage batteries should be properly boxed and should have the cus- 
tomary care which is necessary to keep them in good working order. 



TRANSMISSION OP POWER. 

The term " Transmission of Poiver," as used by electrical engineers, has 
come to have a conventional meaning which differentiates it from what 
must be considered its full meaning. Any transmission of electric current, 
for whatever practical purpose, whether for lighting, heating, traction, or 
power-driving, must of course be a transmission of power ; but the conven- 
tional meaning of the term as now used by electrical engineers and others 
eliminates many of these objects, and is held to mean simply the trans- 
mission of electric current from a more or less distant point or station to a 
center from which the power is distributed, or to power motors at different 
points in a factory or other installation. While the distances over which 
electric current is transmitted for arc lighting in some large cities and in 
many small places far exceed the length of line of the ordinary or average 
power transmission, yet the former is never alluded to as transmission of 
power. The same condition obtains with traction, the transmission of cur- 
rent covering miles of territory, and yet it is only alluded to as power 
transmission when the current is transmitted from a central point to vari- 
ous sub-stations from which it is distributed. 

The engineering features of transmission of power will all be found 
treated under the separate heads in their respective chapters, and the fol- 
lowing is a short resume of the subject matter. 

Building-: page 

Structural conditions and material . 792 

Motive Power: 

"Water power : Turbines, etc 926 

Steam power : Boilers and appliances 829 

Engines and appliances 916 

Shafting and pulleys 946 

Belting and rope drive 951 

Generators : 

Dynamos : direct current 232 

alternating current 232 

double current 232 

Transmitting- Appliances : 

Switchboards 585 

Transformers, step up 331 

Rotaries 286 

Cables and pole lines 92 

Conduits, etc 203 

Distributing* Appliances : 

Sub-stations and terminal houses 331 

Transformers, step down 331 

Switchboards, high tension and secondary 331 

Rotary converters 286 

Direct current motors 270 

Synchronous motors 281 

Induction motors 274 

Frequency changers 274 

Distributing circuits 92 

548 



.. 



DISTRIBUTING APPLIANCES. 



549 



Much has been written regarding the relative values of the different 
methods of transmitting power, and comparison is often made between the 
following types, i.e., 

a. Wire rope transmission. 

b. Hydraulic transmission, high pressure. 

c. Hydraulic transmission, low pressure. 

d. Compressed air transmission. 

e. Steam distribution for power. 

f. Gas transmission. 

g. Electrical transmission. 

All of the first six methods listed have so many limitations as to distance, 
efficiency, adaptability, elasticity, etc., that electricity is fast becoming the 
standard method. The matter of efficiency alone is one of the best argu- 
ments in its favor, and I take from Dr. Bell's book, " Electric Power Trans- 
mission," the following table of the efficiencies such as have been found in 
practice. 



System. 



Per Cent Efficiency at 




Wire rope 

Hydraulic high pressure 

Hydraulic low pressure 

Pneumatic 

Pneumatic reheated, virtual efficiency 
Electric 



For short distances out of doors, transmission by wire rope is much used 
both in the United States and Europe, and where but few spans are neces- 
sary, say less than four, the efficiency is very high. 

Hydraulic transmission is in considerable use in England, but except for 
elevator (lift) service is in little use in the United States. 

Pneumatic transmission is in wide use in Paris, but not so for general 
distribution in the United States, although for shop transmissions for use 
on small cranes and special tools is making good progress. 

Electrical transmission is so elastic and so adaptable to varied uses, and has 
been pushed forward by so good talent, a not small factor, that its progress 
and growth have been simply phenomenal. In one place alone, that of 
traveling cranes for machine shops, it has revolutionized the handling of 
material, and has cheapened the product by enabling more work to be done 
by the same help. 

Electric Power Transmission may be divided into two classes, i.e., long 
distance for which high tension alternating current is exclusively used ; 
and local or short distance transmission for which either direct current or 
polyphase alternating current are both adapted, with the use of the former 
largely predominating, owing perhaps to two factors, a, the much earlier 
development of direct current machinery, and b, to the fact that a large 
number of manufacturers are engaged in the building of direct current 
machinery. Both types of current have their special advantages, and 
engineering opinion is, and will probably remain, divided as to which has the 
greater value. 

Long distance transmission is now accomplished by both three-phase three- 
wire, and by the two-phase four-wire systems, with the former predom- 



50 TRANSMISSION OF POWER. 



ii.ating for the greatest distances, owing to economy of copper. Each sys- 
tem has certain advantages over the other, and both have strong advocates 
among engineers. For the distribution of very large amounts of power the 
three-phase system presents a strong point in its economy of copper, and 
another in simplicity of switching appliances. 

Every case of electric transmission presents its own problem, and needs 
thorough engineering study to decide what system is best adapted for the 
particular case. It is, therefore useless to enter into any detailed discus- 
sion here, as all the engineering details are treated of elsewhere in the book 
under the respective departments. The economic discussion does not enter 
into the engineering problem except in the preliminary study, which has 
presumably been satisfactory before reference is necessary to this book. 

Limitations of Voltage.— While 10,000 volts pressure was used with some 
distrust for a time previous to 1898, since that time 15,000, 20,000, 25,000, and 
40,000 volts have been and are still in use with substantial satisfaction. 

Properly designed glass or porcelain insulators, made of the proper 
material, and tested under high pressure conditions, cause little trouble 
from puncture or leakage. The latter is its own cure, for the reason that 
the leakage of current over the surface of the insulator dries up the mois- 
ture. Dry air, snow, and rain-water are fairly good insulators, and offer no 
difficulties for the ordinary high voltages. Dirt, carbon from locomotive 
smoke, dust from the earth, and such foreign material that may be lodged 
on the insulators, are sure to cause trouble. In the West and some sections 
of the East many insulators are broken by bullets fired by the omnipresent 
marksman. 

Oil insulators have proved worse than useless, as dirt and dust, to say 
nothing of bugs, are gathered by the oil, and produce very bad results'; 
they were introduced in the United States in some of the early high- voltage 
installations, but after a short time the cups holding the oil had to be 
broken off. 

Glass makes the surest insulator, as the eye can make all necessary 
tests ; but it is so fragile that porcelain is more commonly used. It is not 
safe to accept a single porcelain insulator without a test with a pressure at 
least twice as great as that to be used. The interior of the porcelain 
should be perfectly vitreous, and should not absorb red ink so that it can- 
not be wiped off perfectly clean. 

A convenient way of testing such insulators is to invert a number, say a 
dozen, in a pan of salt water ; fill the pinhole with more water of the same 
kind. Connect the pan with one terminal of a high potential transformer, 
and use as the other terminal a piece of metal, say a spike or old battery 
zinc pencil which will be connected to the opposite terminal of the trans- 
former, and inserted in the pinhole of each insulator. A double-pole switch 
should be used to open and close the low-pressure side of the testing trans- 
former. Under these conditions one insulator is tested at a time, and good 
porcelain will stand very high pressure before a breakdown. Heavy sea-fog 
is about as bad a condition as can be assumed for high voltage trans- 
mission. Mr. Ralph D. Mershon of the Westinghouse E. & M'fg. Co. made 
a long series of tests at Telluride, Col., on the high-pressure lines in use 
there. 

At 50,000 volts there will be a brush discharge or leakage from one wire 
to the next that can be seen at night, and makes a hissing noise 
that can be heard a hundred feet or more. This brush discharge 
begins to show at about 20,000 volts, on dark nights, and increases 
very rapidly, as does also the power loss at 50,000 volts and higher. 
This loss depends upon the distance apart of the conductors and their 
size. Above 50,000 volts the losses become serious, the discharge dis- 
posing of a large amount of energy. For these reasons, wires should be 
kept well apart and be of as small size as other properties will allow. 

The wave form of E. M. F. used also influences the brush discharge, being 
the least in effect for sine wave curves of E. M. F., and being much in- 
creased by the use of the sharp, high forms of curve. 

Line inductance, capacity, and resonance, unbalancing of phases, etc., 
have caused little trouble in practice, although they should be given serious 
consideration, especially for lines carrying heavy currents. 

In regard to the frequency to be adopted for power transmission, one has 
to be governed by the case in hand, and the commercial frequencies avail- 
able at economical cost. 



LIMITATIONS OF VOLTAGE. 



551 



Since the success of tlie Niagara plant the frequency used there, 25 per 
second, has become a standard for power transmission purposes, but should 
be avoided if much arc or incandescent lighting is to be done. Other fre- 
quencies, such as 30 and 60, are in common use, tbe latter being the favorite 
for plants having a mixed output of power and lighting. 

It must be remembered that the higher the frequency, the more trouble- 
some are the rotary converters that may be connected to the system. 

Induction motors and synchronous motors of the revolving field type are 
now almost perfection, and are useful to counteract eacb other's effects on 
lines, and both give their best results at low frequencies. Alternating arc 
lamps cannot be used with any satisfaction on a frequency less than 40. 



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Curve for reducing cost of power per maximum horse-power 
per annum in dollars to cost per kilowatt-hour in cents at vari- 
ous load factors. 



STORAGE BATTERIES. 

ELECTRIC STORAGE BATTERIES. 

Partly condensed from articles by Joseph Appleton in " Electrical 
Engineer." 

An electric storage battery, or accumulator, is a combination of cells, eacb 
of which is a unit. 

In the ordinary lead, sulphuric acid type, a cell is made up of three parts 
— the jar, or box, the plates, and the electrolyte. 

Thenar, or containing -box, may be of any good non-conducting and acid- 
proof material of sufficient strength and rigidity to support the plates and the 
electrolyte. In the smaller stationary types the jar is of tenest made of glass 
or of hard rubber, the latter especially for portable cells where lightness is 
of moment. Portable cells are now often made of hard wood lined with 
lead. Large cells for ceutral-station work are made of heavy planks, well 
jointed, and lined with five-pound sheet lead. 

Stationary cells should always be supported upon some well-designed in- 
sulator, such as porcelain, so constructed as to have a retaining-cup of oil, 
in order to maintain a high degree of insulation. They are also generally 
set up from the floor a short distance, most often on stringers of well dried 
and filled hard wood. 

The plates are of two kinds, positive and negative, arranged alternately, 
there always being one more negative than positive. A set or group of these 
plates is commonly known as an element. All positive plates are connected 
together, as are also all negative plates, but the positives and negatives are 
separated from each other by insulating strips of some kind. 

The electrolyte used with all lead batteries — and no others are in exten- 
sive use at the present time — is sulphuric acid diluted with water to a s.g. 
of 1.15 to 1.30 according to the type. The acid must be free from impurities, 
such as arsenic, nitric or hydrochloric acid, and the water must be distilled. 

Storage or secondary batteries of the ordinary lead, sulphuric acid type 
may be divided into two classes, the Plante" and the Faure. Both are lead 
elements in dilute sulphuric acid, but are formed differently. 

The Plante type is constructed of lead plates so designed as to present a 
large surface area to the action of the electrolyte, the active material being 
formed on the plates, either electrically, by charging and discharging, com- 
monly called " forming," or chemically. 

In the Faure, commonly known as the pasted, type the active material is 
applied mechanically to a lead conducting-plate or grid. The material may 
be active when applied, or may be such that it can be converted into active 
material by electrical or chemical formation. 

Plates. 

The positive plate is of lead, upon which a coating of peroxide of lead has 
been formed or mechanically applied. 

The negative plate is of pure lead, the surface of which is spongy or porous 
in its formation. 

The peroxide and spongy lead are the portions of the plates which are sub- 
jected to the chemical action, and are called the active material, the lead 
body of the plates serving practically as a support for the active material. 

The chemical condition of the plates and acid differs when charged and 
discharged. At full charge the positive plate has a dark brown coating of 
peroxide of lead, the negative plates having the porous or spongy condition 
above described, of dark slate color, and the electrolyte being of full specfic 
gravity and strength. In this condition, when the positive and negative 
poles are connected through an external circuit an E.M.F. is set up in the 
cell, a current flowing through the circuit from the positive plate. When 
discharged, the positive plates have a chocolate, and the negative a light 
slate color. A drab color on the positive indicates sulphating or an over dis- 
charge. 

552 






ELECTRIC STORAGE BATTERIES. 



Chemical Action. 

Tlie chemical action taking place during charging is as follows : the cur- 
rent enters at the positive pole, passing through the acid to the negative. 
Both plates contain sulphate of lead, due to the preceding discharge, and 
the net result of the passage of the current is to decompose this sulphate, 
and at the same time to transfer all the oxygen from the negative to the 
positive. At the completion of the charge, the negative is entirely free from 
oxide, and the positive contains no oxide lower than the peroxide, though 
it may still contain some sulphate. The reduction of the sulphate of lead 
forms free sulphuric acid, and, of course, increases the density of the elec- 
trolyte. The complete account of the chemical reactions in charging is too 
extensive to be given here. 

If charging is continued after all the active material has been converted 
to peroxide of lead and spongy lead, oxygen and hydrogen gas will be given 
off in bubbles. 

In discharging, the sulphur radical in the acid combines with the active 
material on both plates, forming sulphate of lead, the specific gravity of the 
electrolyte being reduced. When all the active material has been acted 
upon, the cell is discharged, as an equilibrium has been created between the 
positive and negative plates, and the E.M.F. set up by the chemical action 
has been reduced to zero. In practice the E.M.F. is never allowed to fall 
below 1.8 volts. 

The chemical reactions are given as follows, by Frankland. 

If the buff lead salt be the active material of the battery plates, the fol- 
lowing equations express the electrolytic reactions taking place in the 
cell : — 

I. In charging — 

(a.) Positive Plates. 
S.,Pb 5 14 + 30Ho + 5 = 5Pb0 2 + 3S0 4 H 2 . 
Buff lead. Water. Lead Sulphuric 

Peroxide. Acid. 



(b.) Negative Plates. 
S 3 Pb 5 14 +5H 3 = 5Pb + 3S0 4 H 2 +20H 2 . 



II. In discharging — 

(a.) Positive Plates. 
5Pb0 2 + 3S0 4 H 2 +5H 2 = S 3 Pb 5 14 + 80H 2 . 

(b.) Negative Plates. 
5Pb + 3S0 4 H 2 + 5 = S 3 Pb 5 14 + 30H 2 . 

If the red lead salt be the active material, then the following equations 
express the same electrolytic reactions : — 

I. In charging — 

(a.) Positive Plates. 
S 2 Pb,O 10 + 2 + 20H 2 = 3Pb0 2 + 2S0 4 H 2 . 
Red lead Lead Sulphuric 

Salt. Peroxide. Acid. 

(b.) Negative Plates. 
S 2 Pb 3 O 10 + 4H 2 = 3Pb + 2S0 4 H 2 + 20H 2 . 

II. In discharging — 

(a.) Positive Plates. 
3Pb0 2 + 2S0 4 H 2 + 2H 2 = S 2 Pb 3 O 10 + 40H 2 . 

(b.) Negative Plates. 
3Pb + 2S0 4 H 2 + 20 2 = S 2 P 3 O 10 + 2H 2 . 



554 STORAGE BATTERIES. 



It is, however, very questionable whether these salts play any important 
role in the normal reaction of the cell. 

The various oxides of lead are as follows : — 

Plumbous or sub-oxide Pb 2 0. 

Plumbic oxide, litharge PbO. 

Triplumbic oxide, or red lead minium Pb,0 4 . 

Diplumbic oxide . Pb^. 

Monoplumbic dioxide, or peroxide PbG 2 . 

CiXCriATIOS ©E E.M.I'. ©JF §!ORAtiE BAIIER1, 

Streintz. 
Let J£=:E.M.F. required. 

S=. Specific gravity of the electrolyte. 

s = Specific gravity of water at the temperature of observation. 
Then E= 1.850 + .917 (S — s). 

Wade. 

JF"=work in joules. 

Q= coulombs of electricity passed through the electrolyte. 
H= number of calories liberated by the recombination of a unit 
weight of one of the decomposed ions. 
e — its electro-chemical equivalent. 
c =. its chemical equivalent. 

h = electro-chemical equivalent of hydrogen = .00001038. 
J= Joule's coefficient = 4.2. 
2? = E.M.F. required. 
Then W— QE = QJeH. 
E — JeH. 
e = hc. 

E = JhcH=i.2x. 00001038 cH~ .0000436 cH. 
_heat of formation 

valency 
_ .0000436 X heat of formation 
— valency 

„ 14 . .0000436 X 46,000 

lvoltrr ^ 

heat of formation in calories 

Y— " 46,000 

CAICUIATIOHr OP THE CAPACITY ©E A 
ITOKAOE BATTERY II AMJPEJRE HOERS. 

The current in ampere hours maintained by the consumption of any given 
chemical substance varies with the change of valence and inversely with 
the molecular weights of the transforming substance. The combustion 
of liberation of 1 pound of hydrogen corresponds to 12,160 ampere hours. 
The theoretical capacity in ampere hours may be calculated as follows : — 
V= change of valence of the ions. 
W= the sum of the molecular weights affected. 
12,160 = capacity per pound of hydrogen. 

lnen Capacity per pound = == 

In lead-lead-sulphuric acid cells the above formula gives 40.24 ampere hours 
as the capacity per pound of lead sulphate. 

The above formula is based on the supposition that the entire material of 
both plates is transformed into lead sulphate. This is never accomplished, 
and Fitzgerald gives as a safe rule : 

.53 oz. lead peroxide and the same weight of spongy lead per 

ampere hour for a 10-hour rate of discharge, 
.62 oz. for a 5-hour rate, 
.70 oz. for a 3-hour rate, 
1 oz. for a 1-hour rate. 
All above for the ordinary thickness and an electrolytic density of 1,200. 



THE HYDROMETER. 



555 



THE HYDROMETER. 

The hydrometer is an instrument for determining the density of liquids. 
It is usually made of glass, and consists of three parts: (1) the upper part, 
a graduated stem or fine tube of uniform diameter ; (2) a bulb, or enlarge- 
ment of the tube, containing air ; and (3) a small bulb at the bottom, con- 
taining shot or mercury, which causes the instrument to float in a vertical 
position. The graduations are figures, representing eitber specific gravities 
or the numbers of an arbitrary scale, as in Beaume's, Twaddell's, Beck's, and 
otber hydrometers. 

There is a tendency to discard all hydrometers with arbitrary scales, and 
to use only those which read in terms of specific gravity directly. This ten- 
dency is all the more to be indorsed, as there are considerable discrepancies 
in the different tables professing to give the Beaum£ scale, the following one 
being, perhaps, as much quoted as any. 



Beaume's Hydrometer and Specific Grat 


tries Compared. 




Liquids 


Liquids 




Liquids 


Liquids 


m "® 


Liquids 


Liquids 


© a 


Heavier 


Lighter 


© d 


Heavier 


Lighter 
than 


Heavier 


Lighter 
than 


£3 


than 


than 


ft* 


than 


£3 


than 


MS 


Water, 


Water, 


MS 


Water, 


Water, 


bCoS 


Water, 


Water, 


QS 


sp. gr. 


sp. gr. 


fisq 


sp. gr. 


sp. gr. 


PW 


sp. gr. 


sp. gr. 





1.000 




19 


1.143 


.942 


38 


1.333 


.839 


1 


1.007 




20 


1.152 


.936 


39 


1.345 


.834 


2 


1.013 




21 


1.160 


.930 


40 


1.357 


.830 


3 


1.020 




22 


1.169 


.924 


41 


1.369 


.825 


4 


1.027 




23 


1.178 


.918 


42 


1.382 


.820 


5 


1.034 




24 


1.188 


.913 


44 


1.407 


.811 


6 


1.041 




25 


1.197 


.907 


46 


1.434 


.802 


7 


1.048 




26 


1.206 


.901 


48 


1,462 


.794 


8 


1.056 




27 


1.216 


.896 


50 


1.490 


.785 


9 


1.063 




28 


1.226 


.890 


52 


1.520 


.777 


10 


1.070 


1.000 


29 


1.236 


.885 


54 


1.551 


.768 


11 


1.078 


.993 


30 


1.246 


.880 


56 


1.583 


.760 


12 


1.086 


.986 


31 


1.256 


.874 


58 


1.617 


.753 


13 


1.094 


.980 


32 


1.267 


.869 


60 


1.652 


.745 


14 


1.101 


.973 


33 


1.277 


.864 


65 


1.747 




15 


1.109 


.967 


34 


1.288 


.859 


70 


1.854 




16 


1.118 


.960 


35 


1.299 


.854 


75 


1.974 




17 


1.126 


.954 


36 


1.310 


.849 


76 


2.000 




18 


1.134 


.948 


37 


1.322 


.884 









Streng-th 


of Dilute Sulphuric 


Acid of 


Different Densities 




at 15° C. (59° F0. (Otto.) 




Per Cent. 


Specific 


Per Cent. 


Per Cent. 


Specific 


Per Cent. 


of H 2 S0 4 . 


Gravity. 


of S0 3 . 


of H,S0 4 . 


Gravity. 


of S0 3 


100 


1.842 


81.63 


23 


1.167 


18.77 


40 


1.306 


32.65 


22 


1.159 


17.95 


31 


1.231 


25.30 


21 


1.151 


17.40 


30 


1.223 


24.49 


20 


1.144 


16.32 


29 


1.215 


23.67 


19 


1.136 


15.51 


28 


1.206 


22.85 


18 


1.129 


14.69 


27 


1.198 


22.03 


17 


1.121 


13.87 


26 


1.190 


21.22 


16 


1.116 


13.06 


25 


1.182 


20.40 


15 


1.106 


12.24 


24 


1.174 


19.58 


14 


1.098 


11.42 



Ordinarily in Accumulators the densities of the Dilute Acid vary between 
1.150 and 1.230. 



556 



STORAGE BATTERIES. 



Conducting- Power of Dilute Sulphuric 
Acid of Various Strengths. (Matthhessen). 





Sulphuric 




Relative 


Specific 


Acid in 


Temperature. 


Resistances. 


Gravity. 


100 parts 


0.° 


Ohms per 




by Weight. 




cub. centim. 


1.003 


0.5 


16.1 


18.01 


1.018 


2.2 


15.2 


5.47 


1.053 


7.9 


13.7 


1.884 


1.080 


12.0 


12.8 


1.368 


1.147 


20.8 


13.6 


.960 


1.190 


26.4 


13.0 


.871 


1.215 


29.6 


12.3 


.830 


1.225 


30.9 


13.6 


.862 


1.252 


34.3 


13.5 


.874 


1.277 


37.3 




.930 


1.348 


45.4 


17.9 


.973 


1.393 


50.5 


14.5 


1.086 


1.492 


60.6 


13.8 


1.549 


1.638 


73.7 


14.3 


2.786 


1.726 


81.2 


16.3 


4.337 


1.827 


92.7 


14.3 


5.320 


1.838 


100.0 







Conducting* Power of Acid and Saline 
Solutions. 

Copper (Metallic) at 66° F 100,000,000. 

Sulphuric Acid 1 Measure "1 

Water 11 Measures o ft „„„„^ m „i. 

(Equal to 14.32 parts by weight of Acid f yb * u approximate. 

in 100 parts of the mixture), at 66° F. . .J 
Sulphate of Copper, saturated solution at ) R <• u 

66° F j w 

Chloride of Sodium, saturated solution at L rn 

66° F S 60 " 

Sulphate of Zinc, saturated solution at 1 c a 

66° F f "■* 



INSTALLATION AID CARE. 



Fig. 2. 

Standard 
Hydrom- 
eter. 
8| inches 
long. 



Tn small batteries, in which the cells are small enough to be 
handled when assembled, the cells may all be assembled before 
placing. Large cells have to be assembled in place, as they will 
seldom permit change of position without considerable incon- 
venience. 

The battery -room should be dry, well lighted and ventilated, and 
of moderate temperature, as the evaporation of electrolyte is apt to be 
troublesome in heated rooms. 

All exposed ironwork should be painted with an acid-proof paint; in fact, 
all metal work exposed to the acid fumes should be painted for its protection. 

The floor of the battery room is preferably of brick, tile, or cement, laid 
so it will drain easily to some common outlet. Wooden floors should never 
be used unless protected by lead trays to catch any stray acid. 

The battery room should preferably be located as near the power-house as 
possible, thus reducing the cost of connecting conductors, and possibly using 
the same attendants. 



INSTALLATION AND CARE. 557 



Cells should be arranged so as to be easily accessible for examination and 
repairs. Large cells are seldom placed in more than one tier, but the smaller 
ones can be erected in two or three tiers. 

Where cells are of glass they may be conveniently set In trays on a bed of 
sand, and the trays be set on insulators. Wooden tanks are set directly on 
insulators, as they are always built of sufficient strength to support their 
weight and contents. 

Cell Connections. 

In small cells the plates of one polarity are usually connected by a lead 
strap that is cast on the plates in a bunch, the strap of one cell being con- 
nected to that of the next by a bolt or screw clamp or weld. All battery con- 
nections should be of ample sectional area to avoid loss, and, as lead is the 
metal mostly used for such purposes, and as compared with copper has 
about seven times the resistance, it is especially important that its area 
be large. 

The best method of connecting the positive group of plates to the adjacent 
group of negative plates in the next cell is to bum or weld the two to a lead 
strap of large cross-section ; and, in case of very heavy currents, a copper 
conductor may be embedded in this lead strap. 

JLead-Rurning- Apparatus. 

The hydrogen flame has the special property of not oxidizing, or otherwise 
soiling the lead, and is therefore used for melting together two lead surfaces, 
notably that between cells and the sheet lead lining of the tanks. 

Hydrogen gas is generated in a vessel from sulphuric acid and zinc. The 
gas is collected and passed through a water bottle to a burner, where it is 
mixed with air that has been forced into the burner by a pump or bellows, 
the mixture being ignited for the welding. 

The use of this burner requires some skill and practice, especially in join- 
ing the edges of sheet lead, as it is very apt to burn away. All plate ter- 
minals, and all lead connections of any kind, must be scraped clean before 
connecting up. 

Acid. 

Sulphuric acid made from pyrites is not suitable for storage battery use ; 
only that made from sulphur should be used. Ordinary sulphuric acid con- 
tains many impurities that are apt to be injurious to the plates, notably, 
copper, iron, arsenic, nitric and hydrochloric acids. 

The acid should only be diluted with pure distilled water, and the acid 
should always be poured into the water, and never vice versa. Mix carefully, 
as much heat is generated. 

Tests for Impurities. 

Conner and Arsenic. —To a fresh solution of hydrogen sulphide, 
H S add an equal quantity of the diluted electrolyte, which must be diluted 
far enough so that no white precipitate is thrown down. A black precipi- 
tate generally shows presence of copper, although it may be lead, if the acid 
has already been used in batteries ; a yellow precipitate shows presence of 

¥roii. — To a small quantity of the diluted electrolyte add a few drops of 
nitric acid, HNO,, and heat; when cold add a few drops of solution of potas- 
sium -sulphocyamde, KCNS; the presence of iron will be shown by a deep 
red color. f , 

IVitric Acid. — Make up a solution or diphenylamine, NH(C 6 l± 5 ; 2 as 101- 
I6ws : i gm. NH(C,H 5 ) 2 , 100 cc. strong sulphuric acid. H 2 SO. t , 20 cc. or water 
H,0; to a small quantity of this solution, in a test tube, add a small quantity 
of the diluted electrolyte, which must not have been in use; the presence 
of nitric acid will be indicated by the appearance of a blue color. 

Hydrochloric Acid. — To a small quantity of the proposed diluted 
electrolyte add two or three drops of nitric acid, HNO :! , heat this in a test 
tube, then let it cool; now add two or three drops of nitrate of silver, AgNO.,. 
The presence of hydrochloric acid will be indicated by precipitated or 
cloudy appearance. 



558 



STORAGE BATTERIES. 



first Charge. 

Charging current should always be ready for application when the electro- 
lyte is put in the cells, as it injures plates to stand in the acid without being 
charged. 

The first charge should be carried on for a much longer period than any 
of the subsequent or working charges, as it virtually completes the forma- 
tion of the plates. 

See that the positive pole of the charging dynamo is connected to the posi- 
tive pole of the battery. 

The voltage of charging commences at about 2 volts per cell, and rises to 
2.6 volts at the full charge while taking current at the normal rate shown 
on the maker's lists. 

The curves in Fig. 3 show the voltage of a cell during charge and discharge 
at the normal rate. 

Continue the first charge for at least 10 consecutive hours, and 20 or 30 
would be preferable. The first charge is usually about twice the capacity of 
a battery, and should be made at the normal rate. 



.......... ...__...--_.. „._.... _-_ :: ------ 




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1 i i i i i i ii in i > ■ 




16'' Ml ' I ' 


1,0 I , M 








1..1 I 1 II 1 1. ! 1 1 1 1 , 1 1 M 



HOURS 

Fig. 3. 



This cut shows the general forms of the charge and discharge curves at 
any rate; but in commercial use cells are almost always worked at much 
higher rate than shown in the cut, and give lower efficiencies. For exam- 
ple, a five-hour rate of discharge is quite usual, and in some cases even 
higher rates. Some of the larger users of the Electric Storage Battery 
Company's cells usually overcharge 15 per cent. So the ampere efficiency is 
85 per cent, and the watt efficiency about 72 per cent. 

The specific gravity of the electrolyte will drop during the first few hours 
of the first charge, but will rise again, as the process continues, until its 
maximum point is reached at full charge. If the s. g. be 1.000 at the start 
it will decrease to about 1.180, and rise again to about 1.210 at full charge. 

As the charge nears completion, bubbles of gas will rise from both plates, 
and the charging current should then be reduced, as the active material is 
becoming fully formed, and cannot take up all the gas set free from the de- 
composition of the acid. As the amount of gas liberated is in proportion to 
the current flowing gasing will decrease as the current is decreased. 

It is especially important with the pasted plates that charging be com- 
menced immediately after the electrolyte is put in, as the plates are apt to 
sulphate otherwise, sulphating being the formation of a coating of sulphate 
of lead between the grid and the active material, which practically insulates 
the two from each other, and is very difficult to reduce. Sulphatiiig will also 
occur with pasted plates if discharged too low. The plante form of plate is 
not so susceptible to injury from sulphating. 



INSTALLATION AND CARE. 



559 



It will take 20 or 30 discharges to fit a new battery to give its full ca- 
pacity, and it is well to charge for 25 per cent longer time at normal rate 
for the first few months. In ordinary work the battery will retain its nor- 
mal condition with a charge of 10 per cent in excess of the discharge. 

Creineral Charging". 

During ordinary charging of the battery keep in view the following 
points : — 

Charge at normal rate, or lower, except in emergency. 

Under normal charging conditions 2.5 volt6 may be considered full charge, 
although it can be charged higher than this on an over-charge. 

The specific gravity of the electrolyte is a good indication of the condition 
of the cell; but care must be taken that it is of uniform density throughout, 
as during charging the electrolyte at the bottom of the cell will become 
denser unless agitated, as the sulphuric acid liberated from the active mate- 
rial falls to the bottom. 

The water in the electrolyte will evaporate, exposing the top of the plates, 
unless replaced, which should be done through a hose or tube reaching to the 
bottom of the cell, as water added otherwise will stay on top, being lighter 
than the acid. 

The specific gravity of its electrolyte is the best possible guide to the con- 
dition of a cell, as it may .appear fully charged by gasing and by the voltage, 
and yet its condition be such as to cause these appearances when only partly 
charged. As the hydrometer measures the density of the liquid in the 
upper part of the cell only, care must be taken that the electrolyte be 
stirred up so that the density will be the same throughout the cell, or nearly 



AMPERE HOURS 



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A\ / 




1 ' ^z 


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1 ' / 


i % i 




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AMPERE HOURS 




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SPECIFIC GRAVITY 

Fig. 4. Curve of Specific Gravity at Charge and Discharge. 



so ; of course the difference will be greater in the deeper cells. As the den- 
sity of the electrolyte is due to the sulphuric acid in it, and the sulphuric 
acid is liberated from the active material in proportion to the charge given, 
the s. g is always a true indication of the condition of the cell as to its 
charge. 

Although not always the most economical, the highest efficiency and 
longest life are obtained when the battery is charged slowly, never exceeding 
the normal rate. Conditions of plant operation will determine the most 
economical method for each installation. 



560 



STORAGE BATTERIES. 



Each cell should be tested with a voltmeter and hydrometer once a week. 
Any cell found with voltage low should be examined thoroughly for any 
foreign substance that may have short-circuited it. This will be indicated 
by low specific gravity and' lack of gas given off, and voltage rising slowly 
at the end of a charge, when it should rise quickly. 

Always reduce charging current near the end. of charging, so as not to 
waste energy by escape of gas. 



4000 


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O3000 


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= 


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400 600 800 1000 1200 1400 1600 1300 2000 

AMPERES AMPERES 

CAPACITY CURVE 

Fig. 5. Curve of Variation of Capacity. 

"When discharging at normal rates, never discharge a battery below 1.8 
volt. In discharging at high rates 1.8 volt will be reached before the bat- 
tery is discharged to the same condition as at normal discharge owing to 
the internal resistance, producing a greater fall of potential in accordance 
with the IE law. 

Capacity at Different Rates of Rischarg-e. 

The output capacity of a battery will decrease as the rate of discharge 
increases; but the efficiency will not, as commonly supposed, decrease in 
the same degree, as the decrease in capacity is due to the fact that at 
high discharge rates the point is soon reached where the cell is unable to 
maintain the rate of discharge. But when apparently completely exhausted 
at a high rate, a cell will still furnish current at a lower rate, and on re- 
charging it will be found that only the amount taken out, plus the usual 
excess, is necessary to recover the full capacity. The internal losses, how- 
ever, are greater at high rates, which reduces the efficiency to some extent. 

If cells are given short periods of time to recuperate, during excessive dis- 
charge, they will give practically the same capacity as at normal discharge. 

The General Electric Company is now making a recording wattmeter, es- 
pecially adapted for storage batteries, that will show at all times the amount 
of energy in the battery, as its reading will decrease with discharge and in- 
crease as a charge is put in. 

Never allow a battery to stand without charge ; even half charge is better 
than none, and full charge is much the best. 



SOME OF THE ADVANTAGES OF STORAGE 
BATTERIES. 

For Central Station. 

The chief points of advantage are : 

(1.) Reduction in coal consumption and general operating expenses, due to 
the generating machinery being run at point of greatest economy while in 
service, and being shut down entirely during hours of light load, the bat- 
tery supplying the whole of the current. 

(2.) The possibility of obtaining good regulation in pressure during fluc- 
tuations in load, especially when the day load consists largely of elevators, 
and similar disturbing elements. 

(3.) To meet sudden demands which arise unexpectedly, as in the case of 



UNPACKING, SETTING UP, AND USING. 561 

darkness caused by storm or thunder showers ; also in case of emergency 
due to accident or stoppage of generating plant. 

(4.) Smaller generating plant required where the battery takes the peak of 
the load, which usually only lasts for a few hours, and yet where no battery 
is used, necessitates sufficient generators, etc., being installed to provide for 
the maximum output which, in many cases, is about double the normal 
output. 

All the above advantages apply quite as well to batteries in the power- 
house of street railways, and for maintaining the voltage at or near the end 
of a branch they are of inestimable benefit. 

They can be so installed as to take care of both railway and lighting load, 
as is done at Easton, Pa. 

Eor large Office Building's. 

Many of the same advantages mentioned in the above paragraphs apply 
quite as well to large isolated plants ; some of those in the modern office- 
building being much more extensive than a large proportion of the central 
stations throughout the country. 

In many such plants the night operatives can be dispensed with, as the 
battery will take all the lighting load. 

The load-peak on most office buildings is pretty heavy between four and 
six o'clock in the winter afternoons, and will run up very rapidly if a 
shower comes up in summer, sometimes getting ahead of extra engines. The 
storage battery can always take the load until new generators can be started. 

Running the dynamos at a more even load is also more economical. 

For Small Isolated Plants. 

For country residences and the like, where buildings are far from any cen- 
tral supply, a dynamo or two run by a gas or oil engine, with batteries used 
for storing the output, enables one to have all the advantages of the current, 
and with comparatively little care, as the plant need be run but once or 
twice per week in order to keep the battery stored. This is of especial ad- 
vantage when there is a small water-power. 

Telephone and Telegraph. 

Many storage cells are now in use in telegraph and telephone work, where 
they have replaced many hundreds, if not thousands, of gravity cells. 

Miscellaneous Uses. 

For the horseless or motor carriage storage batteries are well adapted, 
and are in considerable use. 

Train-lighting is done to a small extent by storage batteries. 

Launches for lakes and rivers are now "often propelled by storage bat- 
teries. 

Street-cars are occasionally equipped with storage batteries, and in some 
localities have had a precarious success. 

INSTRUCTIONS FOR UNPACKING, SETTING UP, 
ASB USING STORAGE RATTERIES. 

(By the Electric Storage Battery Company.) 

1. The elements are packed in the following way : one set of each positive 
and negative plates, i.e., a complete element, is packed together in posi- 
tion with sheets of paper and pieces of wood between the plates. A piece 
of string is tied around same to keep it compact and tight (see illustration, 
Fig. 6). Take the elements out of the packing cases carefully, and see 
that they are free from all dirt and foreign material. Place each element 
on a piece of wood, as shown in Fig. 7; cut the string and take out 
the paper and wood. Space the plates so that the separating rings can be 
placed in position on the positive plates, two to each positive plate. Be sure 



562 



STORAGE BATTERIES. 



that the containing jar is clean before placing the element in it. In setting 
up the larger elements it is advisable to tie a piece of string around the ele- 
ment after all the rubber separating rings are in position to prevent the 
plates and rings shifting while being placed in the containing-jar. The 
string must, of course, be removed as soon as the element is in the contain- 
ing-jar. 

2. Place cells in position on battery stands. 

3. Scrape the lead lugs before connecting up, so that both surfaces pre- 
sent a bright metallic appearance. 

4. See that all bolt connectors are Avell screwed up, otherwise resistance 
and consequent heating will result. Always be sure that the cells are con- 
nected up in series ; i.e., positive of one cell to negative of the next. 





Pigs. 6 and 7. 

There is always one more negative plate than positive in every cell. The 
negative (pole) plates are of a grayish color, and the positives are gen- 
erally light brown when new. The free pole at one end of the series will, in 
consequence of this, be a positive, that of the other end being a negative. 

5. When all the cells are connected up in this manner, the electrolyte may 
be added, provided the charging current is available. The electrolyte must 
never be allowed to stand for more than two (2) hours in new cells before 
the charging is started. 



To make Acid. 

6. " Oil of Vitriol " is of much higher specific gravity than that required 
for the cells, and must never be used unless diluted. It must be free from 
impurities, such as arsenic, nitric or hydrochloric acid, and must be diluted 
with pure water to a specific gravity of twelve hundred (1,200), or 25° Baume, 
as shown by the hydrometer at a temperature of 60° Fahrenheit. In mix- 
ing the electrolyte, the acid must always be poured into the water, and never 
the water into the acid. 

7. Always see that the electrolyte is cold before pouring into the cells. 
It is advisable to mix it at least twelve (12) hours before using. 

8. The initial charge must be commenced immediately the cells are filled 
at about one-third (-J-) of the normal rating for four (4) hours, then increased 
to the normal current, at which it should be continued for twenty (20) con- 
secutive hours, if not longer, until the positive plates are of a dark brown 
color, and the voltage is 2.0 volts per cell while charging at the normal rate. 
If possible do not stop charging at the above period, but continue at a 
lower rate, gradually reducing the charging current until one-fourth (J) of 
the normal rate is reached, at which rate it should be continued until the 
cells reach a voltage of 2.6 volts per cell. 

9. In subsequent charges and in general use, it is only necessary to charge 
until the voltage is 2.5 per cell while charging. It is advisable to charge 
the cells once a week until the voltage per cell is 2.5 volts on about one- 
third (-£) the normal charging rate. 

10. The cells maybe discharged down to 1.8 volt per cell, on closed cir- 
cuit at normal rate ; but their efficiency and life will be improved if the 
discharge is not regularly carried to this point, but is stopped before the 



UNPACKING, SETTING- UP, AND USING. 563 



cells become so nearly emptied. The cells must never be allowed to stand 
idle if more than seventy-five (75) per cent of their capacity has been used. 

11. If a battery is to remain idle for a long time, it should first be fully 
charged and then given a recharge, enough to bring it to a boil, at least once 
a week. If, for any reason, this weekly charge is impossible, the battery 
should be thoroughly charged ; then syphon the electrolyte from each cell, 
being sure to refill each cell with water immediately thereafter. Then start 
discharging the battery at its normal rate, which will only last a few hours ; 
then decrease the resistance in the battery circuit until it is almost short- 
circuited. The battery should be in the water about thirty-six (36) hours, 
the acidulated water being then drawn off. 

12. To put the cells in commission again, replace the electrolyte, and pro- 
ceed as per instructions for first charge. 

13. The specific gravity of the electrolyte should be twelve hundred (1,200), 
or 25° Baume, Avhen the cells are fully charged. 

II. Always see that the plates are well covered with electrolyte. 

15. The cells should be individually tested at regular intervals with a low- 
reading voltmeter and a hydrometer. It is very essential that the voltage 
of each cell should be recorded at the end of every charge and discharge. If 
any cell reads low, give it immediate attention, as otherwise serious results 
may ensue. 

Partial Iiist of Manufacturers of Storagre Batteries. 
United States. 

Electric Storage Battei'y Company, Philadelphia, Pa. 
Electro-chemical Storage Battery Company, New York, N. Y. 
American Battery Company, Chicago, 111. 
Willard Electric and Battery Company, Cleveland, O. 
Gould Storage Battery Company, Depew, N. Y. 

England. 

The Electrical Power Storage Company. 
Chloride Electrical Storage Syndicate. 
D. P. Accumulator Company. 
Crompton & Howell. 
Epstein Company. 

France. 

Societe Anonyme pour le Travail Electrique des Meteaux. 

Germany. 
The Tudor Company. 

JBattery for Private Residence. 

The battery should have a capacity to supply one-half the lamps wired for 
eight or ten hours on one charge. The average use is much less, and the 
battery will supply ordinary calls for two or three days on a charge. 

The capacity of the engine and dynamo should be equal to that of the bat- 
tery at the eight-hour discharge rate, so that on special occasions, when all 
the lamps are needed, both dynamo and battery can supply current together. 

The best method of installation will be dictated by local conditions, but, 
up to 200 lamps capacity, a shunt-wound dynamo that will give 150 volts 
pressure is probably the best. 

The best method of regulating a plant of this small capacity is by counter 
E.M.F. cells, placed in series between the battery and lamps, being all in 
when the battery is fully charged, and cut out one at a time as the pressure 
falls. 

Counter E.M.F. cells are simply unformed lead plates, mounted in the 
same manner as are the regular plates, and placed in opposition to the regu- 
lar battery. 

The use of counter E.M.F. cells enables one to charge the battery at the 
same time that lights are being supplied from it, as the counter E.M.F. cells 
Will absorb the extra pressure necessary for charging. 



564 



STORAGE BATTERIES. 



Where it is desired to charge the hattery at the same time that lamps are 
operated, 18 counter E.M.E. cells are necessary; hut where the battery can 
be charged when lights are not in use, as is* easily done in the ordinary 
house, but 7 counter E.M.F. cells are necessary. 

The cuts following show two methods of controlling the pressure, the first 
diagram being with the use of counter E.M.F. cells as described above, while 



r? r 



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O O [ 



DYNAMO RHEOSTAT 



UNDERLOAD 



i VOLTMETER 



O o- 



AMMETER 



,C.E.M.F.CELLS SWITCH 



'IX 



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DIAGRAM of CONNECTIONS 

FOR THE 
PEQUOT LIBRARY, 
SOUTHPORT, CONN. 
THE E.S.B.Co. PHILA, PA. 

Fig. 8. 



BATTERY FOR PRIVATE RESIDENCE. 



565 



the second is done by cutting in and out the end cells. Both diagrams show 
the proper arrangement of all controlling and indicating appliances for a 
switchboard. 




ill 



tHII|!|l |l|l|l|ljl|l p-ffflfHl? 1 

Ausxiva s-nao aN3 

• Fig. 9. 

The method of regulating by cutting in and out end cells is used only in 
plants large enough to afford an attendant, as the end cells are charged and 
discharged to different degrees, and need attention to keep in normal con- 
dition. 

Useful appliances for isolated batteries are underload switches, for auto- 
matically cutting out the battery when it has discharged as low as is safe, 
and overload switches for preventing discharge at greater than a safe rate, 
say in case of a short-circuit on the line. Both devices open the main bat- 
tery circuit and prevent trouble. 



566 



STORAGE BATTERIES. 



Storage Balterj in I<ai'g-« Isolated Plants. 

A large isolated plant, such as is now used in large office buildings, is prac- 
tically a central station with a prescribed territory; and the battery is, in 
this case, an auxiliary, and used for furnishing the peak of the load, and in 
some cases all the load, during such periods of the run as it is within the 
capacity of the battery. 

Experienced judgment is necessary in properly proportioning a storage 
battery to any plant; and it is necessary to know a number of points regard- 
ing its particular features, such as the following ; viz.: — 

1. Nature of load and duration. 

2. Maximum, minimum, and average loads. 

3. Size and type of generating units. 



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WEEK DAY LOAD 

Fig. io. 

Where it is possible to do so, a load diagram constructed from actual 
records of output is in all ways the best, as it will include the information 
necessary, excepting data as to generators and voltage. 

Even in new plants it is nearly always possible for the designing engineer 
to construct a load diagram that will serve Avell for proportioning the battery. 





























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I 



STORAGE BATTERY IN ISOLATED PLANTS. 



567 



Advantages of a Battery in an Isolated Plant. 

1. Generator capacity for the average load is all that is necessary, the bat- 
tery taking the peak ; and if the low load is within the capacity of the bat- 
tery, the generating plant may be run at economical loads only, and shut 
down entirely during the time of low load, providing the battery is then 
fully charged, thus saving fuel. 

2. Lamps may be run on the same lines with elevators or other variable 
load, the battery providing instantaneous regulation. 

3. Greater reliability of plant, and provision for quick supply in case of 
storms and other sudden calls. 

4. Possibility of reduction in pay-roll due to use of battery instead of 
steam plant and generators. 



UNDERLOAD 





PROPOSED ARRANGEMENT 

FOR BELTED BOOSTER, 

WITH END CELL REGULATION 



the electric storage battery co- 

Fig. 12. 

Battery Charge and Control. 

In the large isolated plant and in the central lighting station there are a 
number of methods in common use for operating the battery and controlling 
its output and pressure. 



568 



STORAGE BATTERIES. 



In such plants the dynamos are seldom designed with large enough range 
in voltage to permit of charging the battery direct to its full pressure, and 
recourse is then had to the " booster ; " a belt or motor driven dynamo, 
with its armature in the battery-charging circuit, and its fields being excited 
from the bus bars, which may be used to supply the excess pressure neces- 
sary to produce the proper rise of voltage in the line to overcome the 
counter E.M.F. of the batteries. 

The booster must have a capacity for the full charging current, and a 
range of pressure from ten to fifty volts. 

Following are a number of diagrams of arrangements of batteries in 
actual use, the diagrams showing relative location of all appliances for 
switchboards and battery. These diagrams are furnished by the courtesy 
of the Electric Storage Battery Company of Philadelphia, Pa. 

Belted Booster; 13ml Cell Beg-ulatioii. 

The preceding diagram, Fig. 12, is one of the simplest forms for a plant 
with no special complications, and explains itself. 

Belted Booster; Beg-nlation l»y Counter H.WL.V. Cells. 

The following diagram shows the relative location and arrangement of all 
controlling and indicating appliances for a battery using a belted booster, 
and the regulation being accomplished by counter E. M. F. cells as pre- 
viously described. 




Fig. 13. Diagram of Connections for Plant consisting of Storage Battery, 
C. E.M.F. Cells, Compound Wound Dynamo and Belt-driven Booster. 
TheE. S. B. Co. 



BELTED BOOSTEK. 



569 




SWITCH BOARD PANEL FOR MOTOR DRIVEN BOOSTER 

WITH END CELL REGULATION, 
FOR STORAGE BATTERY IN LARGE PUBLIC BUILDING 
NOTE:- 

ON FIFTEEN POINT VOLTMETER SWITCH POINTS NUMBERED 58, 59, 60, ETC. CONNECT WITH 
CORRESPONDINGLY NUMBERED POINTS OF END CELL SWITCH. ON END CELL SWITCH POINTS 

NUMBERED 57, 58, 59, ETC. CONNECT WITH CORRESPONDINGLY NUMBERED POINTS OF END CELLS. 

Fig. 14, 



570 



STORAGE BATTERIES. 



IVIotor-Driven Booster; End Cell Regulation. 

The preceding diagram (Fig. 14) gives the layout of the switchboard and 
all connections for a storage battery in a large public building. 




^immn ^ r i5mmj 



<y Ky 






DIAGRAM OF CONNECTIONS 

FOR BATTERY BOOSTER AND BOOSTER DYNAMO IN 
CONNECTION WITH C. E. M. F. CELLS AS AN AUXILIARY TO AN 
EXISTING SWITCHBOARD FOR COMPOUND WOUND DYNAMOS. 

Fig. 15. 



MOTOR-DRIVEN BOOSTER. 



571 



Motor-driven Booster; Counter E. M.!". Cell Regulation. 

The preceding diagram shows connections and relative location of appli- 
ances for the switchboard for connection to an existing switchboard ; coun- 
ter E. M. F. cells being used for regulation, with a motor-driven booster for 
charging. 

Note. — On Fifteen Point Voltmeter Switch Points numbered 58,59, 60, 
etc., connect with correspondingly numbered Points of End Cell Switch. 
On End Cell Switch Points numbered 57, 58, 59, etc., connect with corre- 
spondingly numbered Points of End Cells. 

Yacht Plant. 

Yachts cannot carry any surplus weight of machinery ; and in order to 
charge the battery it is often cut in two and the two halves charged in par- 



ITO POINT 



TO POIN" 



{ VOLTMETER 
10 OF CELL SWITCH \ 



( AMMETER J TO POINT* 
\ ,' OF CELL SWITCH 
\ / I — -— 



( AMMETER j | fr^-^^L^I^if 

J O.F^ CELL SWITCH i 



#1 OF 
SWITCH 




DYNAMO 

DIAGRAM OF CONNECTIONS OF SWITCHBOARD, 

FOR PLANT CONSISTING OF STORAGE BATTERIES 

WITH C. E. M.F. CELLS, AND SHUNT OR 

COMPOUND GENERATOR. BATTERY IN TWO PARTS, 

CHARGED AND DISCHARED IN PARALLEL. 

note: on c. e. m. f. cell switch POINTS NUMBERED 1, 2, 3, 4, 

ETC. CONNECT CORRESPONDENTLY NUMBERED POINTS OF C E. M. F. CELLS. 

Fig. 16, 



572 



STORAGE BATTERIES. 



allel from the regular lighting dynamos, counter E. M. F. cells being inserted 
to take up the extra voltage of the dynamo, and to be used for regulation 
when in use on the bus bars. For discharge the cells are again all connected 
in series, and run as usual. 

Note. — On O.E.M.F. Cell Switch Points numbered 1, 2, 3, 4, etc., connect 
with correspondingly numbered points of C.E.M.F. Cells. 



.AMMETER ! 



V V V N \ 

AMMET.EB | , VOLTMETER J , AMMETER | ! AMMETER 



J .AMMETER ' AMMET.EB | , VOLTMETER ! | AMMETE-R | | 'MMtTER | 

SQUAOzfl? 52 tlaUALIZH \W V #OUAL 



til 




-M 



RHIOSTAir KCNAMO 



Fig. 17. Diagram of Connections of Storage Battery Switchboard Panel for 
Yacht " Niagara." The E.S.B. Co., Phila. 

Plant for ITaclit Niag-ara. 

Preceding is the diagram for the connections of battery and switchboard 
for the above-named yacht. This battery is also charged in parallel and dis- 
charged in series, as was the last ; but rheostats are here used for equalizing 
the charging current to the different legs of the battery. 

FLVCTUATISTG POWER LOAD AM» LIGHTS OUT 
THjE SAME DirnTAMO CIRCUIT. 







GENERATOR 



CONSTANT 
CURRENT BOOSTER, 
ADJUSTED FOR AVERAGE 
LOAD ON MOTORS AND 



ELEVATOR8* SHUNT BOOSTER 

WITH BEVERSED SERIES WINDING I 

Fig, 18. Arrangement of Storage Battery and Booster for Circuits havSag 
a Widely Varying Power Load in Connection with Lighting. 



FLUCTUATING POWER LOAD. 



573 



When electric elevators or other appliances taking current intermittently 
are connected to circuits furnishing current for incandescent lamps, there 



l BATTERY AMMETER \ a|, 2 \ 



TO VOLTMETER 




V.M. S. PTS. 3 & 



ill IH 



UNDERLOAD 



LoooaofiOQ 



BATTERY END CELLS 




STARTINS SOX 



CONNECTIONS FOR 

BATTERY, DYNAMO AND BOOSTER 

FOR FLUCTUATING LOAD. 

E-S.BXo. 
Fig. 19. 



574 



STORAGE BATTERIES. 



will be a very considerable fluctuation in the light unless means are fur- 
nished for preventing it. This does not permit of using one dynamo for 
both services unless a storage battery be connected as a regulator. 

The diagram on p. 572 (Fig. 18) shows the scheme of such a connection of 
battery; and the more complete diagram following that gives the actual con- 
nections and diagram of panel board for an existing plant now being worked 
in this manner. 



2 VOLT 
STORAGE BATTERY 




TROLLEY WIRE 



HiliHh ^ 



STORAGE BATTERY 
500 VOLTS 



B B 



RAIL RETURN 



Fig. 20. Arrangement of Battery for Street Railway Circuits where Refine- 
ment of Regulation is not necessary. 




i 



~2L 



CIRCUIT BREAKER 



STORAGE BATTERY REGULATION 

AT DISTANT POINT ON LINE. 

E.S.B. Co. 



Fig. 21. 



STORAGE BATTERY FOR STREET RAILWAYS. 



575 



STOHAftiE BATTERY AS AI'XIIJARI JPOR 
POffEB PLAUTT I'OH STREET RAILWAYS. 

Owing to great fluctuations of load on the power-plant of street railways, 
a storage battery of the proper size and properly connected can be made 
to assist greatly in the economy of the station. 

It will maintain a much evener pressure on the circuits. 

Will take on all overload ; and at the low demand between one and six 
o'clock a.m. will take all the load on all but special occasions, thus relieving 
the #team plant and attendant labor. 

On such occasions, as it may be necessary to shut down the power-plant for 
a short time, the battery will take the entire load for a short period. 

Battery used, for Simple Regulation. 

The two preceding diagrams illustrate the simplest form of application of 
a storage battery to street railway circuits. The first is when the battery is 
placed in the power-house, and in connection with a compound-wound gen- 
erator ; the two cells shown in shunt to the series winding are needed to 
prevent the main battery reacting on the generator. 

The second diagram shows the use of a battery at some distant point 
on the line Avhere it acts as a regulator of pressure, and at the same time a 
regulator of load on the engine. 

Close Regulation, with Rattery and Rooster. 

The following diagram is a sketch of an arrangment of a storage battery 
in connection with a differentially wound booster that will maintain a very 
close pressure on the lines at all times. 

With this arrangement, when a heavy load comes on the circuit the cur- 
rent through the series field of the booster increases the pressure from the 
battery to the line, thus compelling the battery to assist. As the load de- 
creases the series field is overbalanced by the shunt field, and the generator 
then feeds directly into the battery. 

GENERATOR 




UNT 
FIELD 

SHUNT FIELD IS 
CONNECTED IN OPPOSITION TO 
SERIES FIELD, IN BOOSTER . 




Fig. 22. Differential Booster for Maintaining Constant Voltage on Rail- 
way Circuits. 

Rattery for Regulation of Pressure at the End of a 
Eong- Railway feeder. 

The following diagram illustrates the use of a storage battery in main- 
taining a constant pressure at the end of a long railway line, as is done on 
one of the Philadelphia lines at Chestnut Hill. In this case the booster is 
located in the main power-house and charges the battery, which is located a 
number of miles away, through a special feeder at such times as the load is 
light and power is available at the power-house. 



576 



STORAGE BATTERIES. 



BATTERY STATION 





GROUND CJ 



Fig. 23. Diagram Showing Application of Storage Battery to Electric 
Traction, Battery Located at a Distant Substation and Acting as a Load 
Regulator. 

Generator and Battery can feed the system either separately or in com- 
bination through main feeder No. 1, a special feeder No. 2 with Booster 
being used as an adjunct to main feeder, or for independent charging of 
Battery. The E. S. B. Co., Philadelphia, Pa. 

STORAGE BATTERY FOA CKITWAL^TATIO-lf USE. 

All the advantages recited in the preceding paragraphs relating to the use 
of batteries in small and large isolated plants, and in street railway power, 
apply equally well to their use in central lighting stations ; and with some 
refinements not necessary in railway work, they have been found to make 
for increased economy of working in every case where they have been in- 
telligently applied. 

The Edison Illuminating Companies were the first to develop their use on 
this side the Atlantic ; and the growth of such use has been steady, and the 
capacity of batteries has increased to a very great extent since the first 
Tudor battery was installed in the station of the Boston Edison Company. 

Different methods of Application of Battery to Central 
Station Practice. 



,| END CELL SWITCH 

|— 37 tS— 1'- -f BATTERY 

^ r jDI am«Ite t r al mmmmmm 

3 — b — 7 ~ 

vr eno cell Switch 



S.P S.T. SWITCHES 

differential AUMETER 

m 



SWITCH EB 

\ END CELL SWITCH 

_£} 1/ -BATTERY 



11 



END CELL SWITCH 



Fig. 24. 



Circuits of Storage Batteries in Connection with Three-Wire 
System, Philadelphia Edison Station. 



STORAGE BATTERY FOR CENTRAL STATION. 



577 



The three diagrams, Figs. 24, 25, 26, illustrate the straight application of a 
storage battery to use in a central lighting station for all the regular uses 
of regulation of pressure and load, etc. 

The first is the sketch of connections of the plant used in the station of 
the Philadelphia Edison Company ; the second, that of the plant for the 
San Francisco Edison station ; the third, that of the recently installed plant 
of the Chicago Edison Company, the largest by far yet constructed. 




S.P.S.T. SWITCHES 
1876 AMP.„ 
S.P.D.T. SWITCH 



MAIN STAT.IO i AMMETER 



H 



DIFFERENTIAL AMMETER 
Ll£ 



3750 AMR. 

S.P.S.T. switches""" 

1875 AMR , soo ^5p AMp . £nd oell s - w|tch 



.^g. 



IE qLJg gg 

1 [ 25Q0' r 15( 



"S Al m^'r 

r V - BATTERY 



FiG. 25. Storage Batteries in Connection with Three-Wire System 
at£an Francisco Gas and Electric Co., San Francisco, Cal. The 
Co., Phila. 



as used 
E.S.B. 



+ Auxiliary Bus 



^Charging Bus 




-Auxiliary 



— Charging Bus 



Switches c ma. cm ac ma, 



Neutral Switch 



Ji|#|iJi|']i]i|i|i|i|'l'H'|ii>H#H-l-[-l^i 

i4 + Battery 




Battery 



Fig. 26. 



Diagram of Connections of Storage Battery for Chicago Edison Co. 
E. S. B. Co. 



The two diagrams, Figs. 27 and 28, show the circuits and connections of 
batteries in the two large substations of the New York Edison Company ; 
the first is the station at Bowling Green, and the second at 12th Street. 

The second of these substations is right in the heart of the city, and feeds 
in all directions into the heart of the network of conductors. 

The first-mentioned station, that at Bowling Green, is in the lower part of 
the city, and feeds a large district occupied by the large office buildings, and 
keeps up pressure at what was practically the lower end of the network. 



578 



STORAGE BATTERIES. 




-2ND AUX. BUS 



Pig. 27. Battery, Booster, and Feeder Connections, Bowling Green Storage 
Battery Station. 



POSITIVEDYNAMO SWITCHES 




Fig. 28. Battery, Booster, and Line Connections of the 12th Street Station 
of the New York Edison Company. 



STORAGE BATTERY FOR CENTRAL STATION. 



579 



The diagram, Fig. 29, illustrates the method of connecting a storage bat* 
tery to a three-wire system with the dynamos of full pressure and connected 
directly across the outside conductors. This method has been in use abroad 
by tbe Siemens-Halske Company to some extent, and will make a satisfac- 
tory three-wire system from one dynamo or more. 



t t II 



m 



Fig. 29. Diagram of Connections Showing Application of Storage Battery 
to Three Wire System with Generators across Outside Wires Only. The 
E. S. B. Co., Phila., Pa. 

The diagram, Fig. 30, shows one of the newer applications of the storage 
battery for use in connection with long-distance transmission, and it is quite 
similar to the preceding application with the exception that in this case a 
rotary converter is used in place of the regular generator. 

The diagrams, Figs. 31, 32, of the Hartford Electric Lighting Company's 
plant, show a very clever method of using a rotary converter and storage 
battery on a three-wire direct current system. 




Fig. 30. Diagram of Connections for the General Electric Co.'s Exhibit, 
Omaha, Nebraska, Showing Applications of Storage Battery to Three 
Wire System with Generator across Outside Wires Only. The E. S. B. 
Co., Phila. 

The terminals of the direct current side of the rotary are connected to the 
outside wires of the three-wire circuits, and the neutral is carried back of 
the rotary, and connected to the middle of the secondary on each of the 
two or three static transformers. This method works well whether the 
battery is connected or not. 

TEiTIItTG STORAGE BATTERIES. 

Condensed and rearranged from Article by Carl Hering in 
"Electrical World." 

An intelligent test of storage batteries requires a considerable knowledge 
of such batteries, in addition to the mere capacity to make the proper con- 
nections and to read the instruments accurately. The conditions of the test 
are also highly important, and must be Avell understood if the results are to 
be reliable. 

Storage battery tests may in general be separated into two classes; viz. :— 



580 



STORAGE BATTERIES. 



FARMINGION RIVER POWER STATION 

600 K.W. TWO PHASE 
500-VOLT ALTERNATORS 




1200 VOLTS 
SINGLE PHASE 
LIGHTING CIRCUIT 



LINE TO HARTFORD 






5400 VOLTS TWO PHASE 

CIRCUIT FOR LIGHTS AND 

INDUCTION.MOTORS 



DIRECT. COUPLED TO SHAFT 
THAT OPERATES ARC DYNAMOS 

T. GENERATORS 



PEARL STREET 




STATE "STREET" 
STATION FROM WHICH 
SWIRE DIRECT CURRENT 
SYSTEMJS OPERATED 



II 



ROTARY TRANSFORMER 




771 H ' r-LH I T I\ M M H automatic 

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i ( s l^-=-i =1 ir • rr? rnP iyJ fpJ rpJ swiTcHEs 

<§„ 5 = esfellfilU' Aa Aa 1 1a Aa oA <Ja <Ja Aa Aa 

i;3)=< ^ssF^HTU Ml II II I I 



lirnnini 



djfferential 6 k 




AMMETERS L l> 
O o: 

o2 e 


A. AM METER 


V. VOLTMETER 


••ot 
5 3 


C. B. AUTOMATIC CIRCUIT BREAKER 


8.. .SWITCHES. 



Figs. 31 and 32. Connections of Machines and Circuits of Hartford Electric 
Light Company, showing Special Connection of the Storage Battery to 
Rotary Converters. 

a. To determine for a purchaser if the hattery fulfills the specifications 
under which it was furnished. 



TESTING STORAGE BATTERIES. 581 

6. To determine for a maker or prospective investor all the qualities of a 
battery, including its capacity, efficiency, maximum, minimum, and normal 
or best rate of working, both as to charge and discharge. 

The first test should really be included in the second; or, when making it, 
it will be well to carry out as much of the routine of the second test as can 
be done without excessive cost to the client, and anyway as much as may be 
necessary to determine the prescribed results. 

In the second test the operator will necessarily have to determine the con- 
ditions; and it is tberefore highly important that he fully understand the 
peculiarities of storage batteries and their behavior and working, especially 
so where two batteries of different makes are to be compared. 

Following are some of the points to be determined. 

1. Whetber the battery is for stationary or for portable purposes. 

2. Weight of plates, of acid, of containing-cell, of one coupling. 

3. Floor space, accessibility for inspection and repairs. 

4. Size of plates. 

5. Dimensions of containing-cell or box. 

6. Rate of charge, — maximum, best, normal. 

7. Rate of discharge, — maximum, best, normal. 

8. Efficiency at all rates of charge and discharge. 

9. Normal rate of charge per unit of plate surface. 

10. Normal rate of charge per pound of plates, and per pound of cell total. 

11. Normal rate of discharge per unit of plate surface. 

12. Normal rate of discharge per pound of plates and per pound of cell 

total. 

13. Curve of rise of voltage at different rates of charge. 

14. Curve of fall of voltage at different rates of discharge. 

15. Kilowatts capacity at different rates of charging. 

16. Kilowatts capacity at different rates of discharge. 

17. Curve of load value when charging at constant potential. 

18. Curve of load value when charging at constant current. 

19. Curve of specific gravity of acid by hydrometer during charge and dis- 

charge. 

1. The specifications of the manufacturer will essentially determine whether 
the battery is for stationary or portable purposes, except in trials of new 
ones, in Avhich case the person making the test will be in position to say 
from his trials for wbich purpose the battery may be best adapted. 

Batteries for stationary purposes may, in general, be chosen regardless of 
weight and dimensions, bat for portable purposes size and weight must, of a 
necessity, be the smallest commensurate with tbe service demanded. 

2. A knowledge of tbe weight of plates, acid, containing-cell, and one 
coupling is useful in comparing output per unit of weight with other makes 
of battery. 

3. The floor space required, and accessibility for repairs, often govern the 
selection of batteries for special purposes ; and good practice would dictate 
that the cell occupying the least space per unit of output, and the one that 
was repaired with the least trouble, be selected. 

4. The size of plates will determine the output per unit of surface. 

5. Dimensions of the containing jar or box must be known, in order that 
proper space may be laid out for its installation. 

6. In order to adapt a battery to the purposes of its use it is highly impor- 
tant that the maximum and normal rate of charge be known, as the battery 
is most frequently charged during the idle time, or time of lowest output of 
some operating electrical plant. It is sufficiently obvious that where a plant 
is available for but a short time, a battery admitting of a high rate of char- 
ging is desirable, although not always the most efficient in all ways; whereas, 
if there is plenty of time, during which the charging may be done, then the 
battery may be charged at a slower and more efficient rate. 

7. A full knowledge of the maximum and normal rates of discharge is of 
the very highest importance, as on this depends the capacity and good work- 
ing of the battery. 

The capacity of all lead batteries is reduced by hastening the discharge, 
and this is especially so for batteries having the active material in thick 
masses, or so disposed that the acid has not free access to it. In batteries 
having the active material disposed in thin layers, and freely exposed, to the 
action of the acid, the reduction of capacity is not so great. 



582 STORAGE BATTERIES. 

While it may be true that a battery may be constructed for less cost if made 
for low rates of discharge, the capacity is so much reduced when dis- 
charged at high rates, that it seems better policy to construct for high rates 
of discharge, in which case the battery may be equally well used for dis- 
charges at low rates, but will not hold a charge quite so long as will the slow 
discharge battery. Treadwell says 8 amperes per square foot of positive 
plate is a good rate of discharge. 

Theoretically, the capacity of a battery depends upon the amount of 
active material, while the rate of discharge depends upon the amount of 
surface acted upon by the acid. 

In most installations where a storage battery is used, it is essential that the 
battery be capable of a high rate of discharge for a short time, say an hour 
or two, and it is this fact that governs the selection rather than its capacity, 
although this latter condition must receive due attention after the rate of 
discharge is settled. 

In the United States it is now customary to designate the capacity of a 
storage battery by a time rate ; viz., a given battery has a certain capacity, 
at a full discharge in three hours, and such a capacity at a discharge in five 
hours, etc., 8 to 19 inclusive. Nearly all these items are determined by cal- 
culations from the readings of the instruments in use, and need no further 
explanation here. 

The following named readings may be taken as the routine of a test. 

Charge. 
Time. 

Amperes input. 
Volts of charging circuit. 
Specific gravity of acid by hydrometer. 
Temperature of room. 
Temperature of acid. 
Statement of gasing. 

Discharge. 
Time. 

Amperes output. 
Volts at cell terminals. 
Specific gravity of acid by hydrometer. 
Temperature of room. 
Temperature of acid. 
Statement of gasing. 

General Conditions. 

Insulation resistance of cell from ground. 

Resistance of cell between terminals when fully charged and when 
fully discharged. 

If there is a storage battery recording wattmeter available it will be use- 
ful in connection with the readings mentioned above. 

SOURCES OX 1 (IHHMT FOR CHAR«IW«. 

Current from a battery of storage cells will be found by far the best for 
testing a cell or cells. Where one cell is under test, four others of similar 
size connected, two in multiple and two in series, will be found to give good 
results. 

If current from public circuits, or from a dynamo, is to be used, it should 
be as steady as possible, of considerably higher voltage, and have a large 
resistance capable of carrying indefinitely the maximum current in series 
with the cell. 

Before starting a test, it is necessary to decide the points at which the 
battery may be considered charged and discharged, as overcharging and 
undercharging and light and full discharge make much difference in the 
results. 

It is difficult to predetermine a rate at which the battery will be fully 
discharged in a certain time, and the only way is by trial rates. Even 



SOURCES OF CURRENT FOR CHARGING. 583 

then, no rate can be taken as reliable unless it can be repeated under 
the same conditions, any variation in result showing that the battery had 
not recovered from its previous discharge. 

Charging too long at a high rate will injure the plates, but moderate over- 
charging with a small current is beneficial to the plates, though it, of course, 
reduces the efficiency. 

Charging too little results in increased efficiency but less capacity. 

Discharging too far increases the capacity, reduces the efficiency, and re- 
sults in great variations in voltage and a tendency to increase the destructive 
action on the plates. 

Discharging too little increases the efficiency but reduces the capacity. 

Destructive action on the plates determines the limits of charge and dis- 
charge and inside the safe limits the points of stopping charge and discharge 
will depend on whether high efficiency or high capacity is deemed the most 
desirable under the special conditions. The proper stopping point is deter- 
mined by a preliminary test for a curve of voltage, then the points may be 
selected between the points of rapid change in pressure. 

Slow discharge will take out more of the charge than a rapid discharge, 
the latter condition leaving some of the charge in the battery, which may 
show in the next discharge, and make the results erroneous. 

If a rapid discharge be followed by a slow one, the capacity for the second 
test will indicate higher than it ought, in some cases showing an efficiency ex- 
ceeding 100 per cent. 

If a slow discharge be followed by a rapid one, then the capacity of the 
second test will indicate lower than will be the correct result. 

Destructive action on the plates can only be determined by inspection, 
which will show other than normal colors, sulphating, buckling, loosening 
of the active material, etc. A number of discharges may be necessary to 
determine if a certain rate is deleterious. 

In stating the limiting voltages, it is most correct to state the rise or fall 
of voltage in percentage of the initial pressure, taking as such initial pressure 
the reading of voltage a short time after the start to charge or discharge, 
and when it has become constant. The percentage is not always the same 
for charge and discharge. 

For the sake of uniformity, especially in comparing cells, it is best to make 
all tests with continuous discharge without stop. 

It is considered best to charge with constant voltage, but is very difficult 
to do, as the current varies greatly, starting in at a large amount and reducing 
to a small amount at the end of the charge. The current may vary through 
wide limits without much effect on the charging voltage. Varying the 
charging current by steps will be found to result in more nearly constant 
voltage, reducing to a lower value when the voltage indicates a ranid rise. 
Take the time of charge at each rate in order to compute the capacity of 
charge. 

It is best to make the discharge at constant current, as that more nearly 
approaches actual practice. If this is not practicable in the circumstances, 
then the best method is to discharge through a constant resistance. 

Discharge at a constant current will require the use of a rheostat that can 
be changed by very small increments, such as a water box or carbon plate 
resistance. The readings will then be the voltage at the cell terminals and 
the constant amperes, and with a proper rheostat the test is very simple. 

Discharge through a constant resistance, which, by the way, is seldom an 
actual condition, owing to heat variations, the calculations become tedious, 
as they have to be made for each reading, and a careful record kept of the 
time. 

A discharge at constant watts would be the most correct method for bat- 
teries that were to be used for traction, but the calculations and adjust- 
ments are so troublesome and difficult as to add to the liability to error. 

In comparing two cells connect them in series for charge or discharge, cut- 
ting out each one as its work is completed, measuring the voltage at the cell 
terminals. 

In a comparison of different cells it is necessary to base the comparison 
on some common factor, such as the following items, the selection depend- 
ing on the special conditions to be filled: — 
Ampere-hours per pound. 
Watt-hours per pound. 
Charge and discharge rate in hours. 



584 STORAGE BATTERIES. 



Discharge in watt-hours per pound. 
Discharge in ampere-hours per dollar of cost. 
Discharge in watt-hours per dollar of cost. 

Readings of instruments will be governed as to time by the circumstances 
of the test and the quality of the apparatus. If the source of current or the 
rate of discharge is variable, many more readings will be necessary than 
if they are steady. If the instruments do not respond freely to changes 
of current many readings will also be necessary on that account. If all the 
conditions are favorable 15 to 25 readings will be sufficient to give a good 
average. 

Before starting test, take the voltage of the cell on open circuit, as it is 
some indication of the condition of the cell. 

During test take occasional readings of voltage from which to calculate 
the internal resistance of the cell, as follows : first take the voltage of the 
cell while connected in circuit and working, then take the cell out of circuit 
and take voltage on open circuit. 

Connect voltmeter terminals to the lead terminals of the cell, not to the 
circuit or the couplers. 

Connect the amperemeter as close as possible to one terminal of the cell, 
so as to include any leakage. 

Leakage may be found by connecting one leg of the voltmeter to ground 
and the other to one terminal of the cell and then the other. The leak, if 
any, will be found nearest the terminal indicating the least deflection of the 
voltmeter. 

Where the circuit is merely switched from the charging source to the dis- 
charging circuit, it is necessary to reverse the ammeter leads. 

Calculate efficiencies for ampere-hours and watt-hours, and for mean volts, 
as follows: — 

. , _. . ., Discharge in ampere-hours X 100 

Ampere-hour efficiency % = ^-^ : - ; 

Charge m ampere-hours 

_v ^ , ,«. . „ Discharge in watt-hours x 100 

Watt -hour efficiency % = ^z- : — rr 

Charge in watt-hours 

._-„ . „ .. „ Mean volts of discharge X 100 

Efficiency of mean volts % = ^ r- — . , te 

Mean volts of charge 

ttt j.j. r. ^ • /* Mean volt efficiency x ampere-hour efficiency 
Watt-hour efficiency % = ■ — ^ — -• 

Comparing ampere-hour efficiency with mean-volt-efficiency will show 
whether loss in watt-hours is due to polarization and internal resistance, 
or to leakage and gasing or lack of retaining power of the active material. 



SWITCHBOARDS. 

For lig-ht and Power. 

There are two general types of modern switchboards for light and power: 

(1) Those in which all the switching and indicating apparatus is mounted 
directly on switchboards. 

(2) Those in which the main current crying parts are separate or at a 
distance from the controlling and indicating apparatus. Both of these can 
be further divided into Direct Current and Alternating Current, and there 
are numerous and distinct classes under these. 

Modern switchboards are made of slate or marble panels, each having a 
definite function. 

LAYOUT OF §WITCHBOARI)S. 

In laying out buildings for central stations or isolated plants, the switch- 
board should be located in an accessible place, and have plenty of room 
both back and in front. In many cases the switchboard can be placed 
advantageously on a gallery overlooking the machinery. If due considera- 
tion be given to the location of switchboard with respect to the machines 
and feeders which it controls, unnecessary complications and expense can 
be avoided. 

Switchboards are now standardized, covering a large range of D.C. and 
A.C. generators and feeders, although, of course, it is often necessary to 
meet special conditions, which, however, can be met usually by slight modi- 
fications of the standard. 

Unnecessary complications and extra flexibility being at the expense of 
simplicity, are always to be avoided. It would seem unnecessary, for in- 
stance, in the great majority of cases to have more than one set of bus bars. 

Plainness, combined with neatness, and symmetry, is much to be preferred, 
and nothing should be placed on a switchboard which has no other function 
than ornamentation. 

If extensions to switchboards are expected, which is usually the case, 
panels controlling generators should be together at one end of the switch- 
board, and those controlling feeders at the other end. When total output 
panels are used, they are placed between the generator and feeder sections. 
Of course, where switches are controlled at a distance, this rule need not 
be followed ; but, on the other hand, it is often advisable, in order to sim- 
plify station wiring, and to save copper in the busses, to intermingle the 
generator and feeder switches. Even in this case it is desirable to group 
the generator controlling and indicating devices together and likewise those 
for the feeders. For ordinary D.C. switchboards 4 feet is little enough 
behind the panel. In any case, there ought to be a clear space between 
connections on panels and wall, of 2£ to 3 feet. For large work and most 
A.C. work it is very often necessary to have 6 to 8 feet behind panels. 

In the high-tension work of 5000 volts and above, the General Electric 
Company remove all high-tension apparatus from the face of the board ; 
the switches being placed in fire-proof compartments of brick or soapstone, 
and operated mechanically through bell cranks and levers by means of a 
handle on the panel, or electrically by means of a controlling switch. The 
instruments are connected to secondaries of current or potential transform- 
ers, which are placed in some convenient place in connection with the high- 
tension wiring. This, of course, necessitates more room than the ordinary 
switchboards require. The main current carrying apparatus can be placed 
directly behind the controlling board, below in a basement, or under a 
gallery ; or above in a gallery ; or, if switches are electrically or electro- 
pneumatically controlled, they can be placed in any convenient place. 

In locating switches and other appliances, it is usually assumed that 
dynamo leads come from below, and that feeder wires go out overhead, 
except in the case of underground feeders, which naturally go out below. 

COWSTRUCTIOHf. 

Central station switchboards are usually composed of panels about 90" 
high and 2" thick, and varying in width from 16" to 36". The panels are 

585 



586 



SWITCHBOARDS. 



generally in two sections ; the top varying from 60" to 65", and the lower 
from 25" to 30". The General Electric Company's Standard is 62" and 28" 
respectively for top and lower part ; the Westinghouse Standard is 65" and 
25". The General Electric Company also makes panels 76" high, \\" thick 
for isolated plants. Each panel is beveled all around on the front edges 
with a \" to \" bevel. 

Where a well finished switchboard is desired, black enameled slate is 
recommended for circuits of less than 1100 volts. The main current carry- 





FlG. 1. Method of Joining 
Adjacent Panels. 



FlG. 2. Channel Foot for Switch- 
board Frame. 



ing parts are mounted directly on the panel. For higher voltages it is 

necessary to use marble on account of its higher insulating qualities. Plain 
slate can be used where a low-priced switchboard is 
desired for low voltages. 

There are several different varieties of marhle used 
for switchboards, viz. : blue or white Vermont, pink 
or gray Tennessee, and white Italian. Marble being 
a natural product cannot always be matched in shade 
or markings. The colored marbles do not show so 
readily as white marbles the effect of oil or grease, 
and therefore are more suitable for switchboards. 
Of the colored varieties, the blue Vermont marble 
can be obtained in the most uniform color. 

Steel angle bars varying from 1\" x \\" x \" to 3" 
x 2" x \", are ordinarily used for supporting the 
panels, although in some cases for heavy work, steel 
channels, tees, or "I" beams are used. The angle 
bars stand on the floor, to which they are fastened by 
means of a small foot iron. The panels are bolted to 
the narrow web of angle bars, and adjacent angles 
are bolted together through their wide webs (Fig. 1). 
The panels should be set up on a level strip, which 
can be of either hard wood, " I " beams, or an inverted 
channel. 

The frame-work of all switchboards should be in- 
sulated from ground when used on circuits of 600 
volts or less. In high tension A.C. systems it is neces- 
sary to ground all frame-work to carry off static 
discharge and in order to get rid of danger to the 
operator should he accidentally touch the frame- 
work. For securing the structure in a vertical posi- 
tion, rods with turn buckles for adjustment of length 
are run from the back wall to the angle frame, at 
or near the top. A " Y " connection can be made to 

straddle the two angles, and a bolt be put through the whole. The wall 

end can be secured by expansion bolts or other means. 




xiy 2 

Fig. 3. Showing 
Method of Bracing 
Switchboard Panel 
to Wall. 



CONSTRUCTION. 



587 



Circuit breakers should be placed, if possible, near the top of the panel, 
so that there will be no apparatus above them. Instruments should be 
placed within convenient view of attendant, and switches and rheostat 
hand wheels should be located within easy reach. 

It is recommended that illuminating lamps be left off of switchboards, 
and that instruments be illuminated from lights on the front of the 
switchboard. 

The copper bus-bars and connections on the back of switchboards need 
careful laying out, with a view to carrying the current economically and 
without overheating, and above all, in order that there will be no undue 
crowding, and that they will present a neat and workmanlike appearance. 
The tendency has been of late to place the busses toward the top of panels, 
except in the case of small isolated plant switchboards. The switches, cir- 
cuit breakers, and instruments are connected to busses by means of bare 
copper strips or insulated wire, bent in the most convenient shape to suit 
the case. It is not recommended, as a rule, to have long studs on the appara- 
tus projecting out far enough to connect direct to busses, as the strain on the 
switch, due to weight of busses, is likely to affect the adjustment of switch 
contacts. Very often the connection strips are sufficient to rigidly support 
the busses, but in some cases it becomes necessary to provide insulated 
supports for carrying them. Copper bars, flat or round, are now practically 
universal on low-potential boards. Owing to the greater ease in making 
attachments and in adding capacity the flat bar is to be preferred, and a 
thickness of Y'i \", and \" , with width according to the current carrying 
capacity required, is convenient. The size of copper bus-bars and connec- 
tion strips is usually figured on the basis of 1000 amperes per square inch of 
cross-section. By properly laminating the bars, it is safe to use this basis 
even for very heavy current. Contact surface should be figured anywhere 
from 100 to 200 amperes per square inch, according to the method of clamp- 
ing, bolting, or soldering. In clamping or bolting, steel bolts should be 
used. 

Herrick gives the following table as embodying the current practice for 
central stations, based upon a load factor not exceeding 50%. If figuring on 
a 100% load factor, the following amperes must be cut in half : — 

COPPER BAR DATA. 
From " Modern Switchboards," by A. B. Herrick. 



Dimensions. 


Amps. 


Cir. Mils. 


Sq. Mils. 


Ohms 
per Foot. 


Weight, 
per Foot. 


1 xi" 


433 


318,310 


250,000 


.0000336 


.97 


H x i" 


530 


397,290 


312,000 


.0000269 


1.21 


H x i" 


626 


477,465 


375,000 


.0000223 


1.45 


if X \" 
li x t" 

n x t" 


725 


556,400 


437,000 


.0000192 


1.70 


676 


596,830 


468,750 


.0000179 


1.82 


798 


716,200 


562,500 


.0000149 


2.18 


1| X §" 


916 


835,600 


656,250 


.0000128 


2.54 


2 X §" 


1035 


954,930 


750,000 


.0000112 


2.92 


2i x f" 


1154 


1,074,300 


843,750 


.00000995 


3.27 


2 XV 


1222 


1,273,240 


1,000,000 


.00000840 


3.89 


2i X \" 


1500 


1,591,550 


1,250,000 


.00000672 


4.86 


2iXf" 


1715 


1,989,440 


1,562,500 


.00000537 


6.07 


0000 B. & S. 


257 


211,600 




.0000505 


.64 


\" round 


305 


250,000 




.0000428 


.76 


%" round 
f" round 


426 


390,625 




.0000273 


1.18 


560 


562,500 




.0000190 


1.71 


1" round 


861 


1,000,000 




.0000107 


3.05 



For the sake of securing the best conductivity, as far as possible, all 
switchboard connections should be worked out of rolled copper ; but it is 



588 



SWITCHBOARDS. 



occasionally necessary to use copper or brass castings, although their use 
should be avoided as far as possible, as the conductivity is always low, vary- 
ing from 12% to 60% according to mixture. Where necessary to use cast- 
ings, they should be made of new metal only, and care should be taken to 
insist upon a standard of conductivity in each piece if it is to be used where 
such a condition counts. A conductivity of 50% may be considered high 
and sufficient. 

The following table from " Modern Switchboards," by A. B. Herrick, gives 
percentages of mixtures with resulting conductivity as compared with 100% 
copper : — 



% 


% 


Conduc- 


% 


% 


Conduc- 


Copper. 


Zinc. 


tivity. 


Copper. 


Tin. 


tivity. 


98.44 


1.56 


46.88 


98.59 


1.41 


62.46 


94.49 


5.51 


33.32 


93.98 


6.02 


19.68 


88.89 


11.11 


25.50 


90.30 


9.70 


12.19 


86.67 


13.33 


30.90 


89.70 


10.30 


10.21 


82.54 


17.50 


29.20 


88.39 


11.61 


12.10 


75.00 


25.00 


22.08 


87.65 


12.35 


10.15 


73.30 


36.70 


22.27 


85.09 


14.91 


8.82 


67.74 


32.26 


25.40 


16.40 


83.60 


12.76 




100.00 


27.39 




100.00 


11.45 



EQUALIZER BUS 



All minor connections to bus-bars such as switch leads, feeder ends, or in 
fact any attachments whatsoever, whether bolted to, clamped against, or 
soldered, should have ample surface contact, not less than ten (10) times (and 
twenty (20) times is better), the cross-section of the smaller of the two 
conductors connected, and where the sub-connection is of round-section it 
should be cup-soldered or " sweated " into a flat lug having the proper 
amount of surface contact for bolting or clamping to the bus-bar. 

Cup-soldered conductors should enter the socket from two to three 
diameters. While all permanent joints of this nature should be soldered, 

it is sometimes necessary 
to make joints that can 
be easily disconnected, in 
which case the old-style 
socket with binding screws 
may be used, but the con- 
ductor should be entered 
from four (4) to ten (10) 
diameters to make a secure 
connection. 

BUS EXCITED 

DYHTAMOS. 

The diagram (Fig. 4) and 
text on a method of ex- 
citing dynamos from the 
bus-bars, in starting, was 
published by W. B. Potter, 
in the " Electrical Engi- 
neer." Besides being a 
very simple method of bus- 
connecting for excitation, 
if the equalizing switch, 
E.S., and positive switch, 
P.S., are left closed all the 
time, which can be done 
without harm excepting 
when some repairs or changes may be wanted in the dynamo, all equalizing 
connections are left in circuit all the time, and any dynamo that may be 




Excitation of Generators. 



GENERATOR PANEL CONNECTIONS. 



589 




a. 

Fig. 5. Connections of Generator Panels for Direct Current. 300-1800 
Amp. G. E. Co. 



590 



SWITCHBOARDS. 




Fig. 6. Switchboard Panel for One Three-phase Alternating Current Gen- 
erator, to 2500 volts. G. E. Co. 




-- PILOT LAMP 
.FUSE BLOCKS 
A.C. VOLTMETER 




_ EXCITER RHEOSTAT 

__A.C. AMMETER' 

-D.C. FIELD AMMETER 

ELECTROSTATIC 

GROUND DETECTOR 

-VOLTMETER SWITCH 

-SYNCHRONIZING LAMP 

SYNCHRONIZING BUSSES 

—GROUND CONNECTION 

-SYNCHRONIZING PLUG 

"GENERATOR RHEOSTAT 

"CARBON BRtAK FIELD 

SWITCH 

GENERATOR SWITCH 



Fig. 7. Switchboard Panel for One Single-phase Alternating Current Gen- 
erator, to 2500 volts. G. E. Co. 



MANHATTAN RAILWAY SWITCHBOARD. 591 



| 

£ * S » 



ro s a 



t ! jl ^T~P cia i 



i g 



£ 8 J|f|P B fp fp S ; ' 

I b 

CD 




Fig. 8. Diagram of connections for switchboard of main power station 
Manhattan Railway Co., L. B. Stillwell, Cons. Engr. 



592 SWITCHBOARDS. 



running will then take its proper amount of current through its series coil* 
and will, therefore, compound more nearly as it was designed to do, than 
if all the load is on the series coil of the running dynamo. If greater sim- 
plicity is desired, the equalizing switch, E.S., and positive switch, P.S., can 
be one double-pole switch, and the negative switch, N.S., a single pole. 
Leave the double-pole switch closed all the time, and throw the machine 
in and out with N.S. 

Mr. Potter says : — 

By reference to the accompanying diagram, it will be seen that by closing 
the positive switch, P.S. (the equalizer switch, E.S., being closed), the series 
coil of the generator to be started is connected in parallel with the series 
coils of generators in operation, thus separately exciting the field of the 
generator to be started. 

The field switch, F.S., being closed, the voltage is then adjusted by the 
field resistance to correspond with that of the bus, and the more easily so, 
as by this method there is secured a variation of voltage corresponding to 
that due to changes of load on the over-compounded generators in operation. 
This method also insures the polarity being at all times the same as the 
other generators. On closing the negative switch, N.S., and reducing the 
resistance in the shunt field, the generator takes up its load smoothly 
and without the violent fluctuation usually caused by connecting the series 
coils after the full potential has been developed by the shunt field only. 

It is not necessai-y to show here all the standard forms of switchboard, or 
the appliances that are used with them, as changes take place so often that 
any article pictured or described is apt to be out of date in a very short 
time. A few diagrams of standard arrangements that are not subject to 
much change are shown. I have included the diagram of general arrange- 
ment of switchboard connections of the great plant of the Manhattan 
Elevated Railway of New York, as being very simple and of considerable 
interest. 



ARC *W1T< lIKOAItl)*. 

This line of switchboards represents an entirely different construction 
from that of ordinary switchboards. 

Extra flexibility makes it desirable, and small currents make it possible, 
to use plug connections instead of the ordinary type of switches. 

The function of arc switchboards is to enable the transfer of one or more 
arc light circuits to and from any of a number of generators. This trans- 
ferring is sometimes accomplished by means of a pair of plugs connected 
with insulated flexible cable ; sometimes by plugs Avithout cables, which 
bi'idge two contacts back of the board, or by a combination of cable plugs 
and plugs without cables. The type using plugs without cables is pref- 
erable, because danger is eliminated, which would otherwise be possible to 
attendant, due to contact with exposed or abraded cables carrying high- 
potential current. 

The accompanying illustration (Fig. 9) shows an arc switchboard of the 
General Electric panel type, arranged for three machines and three cir- 
cuits. The vertical rows of sockets are lettered and the horizontal num- 
bered. The ends of the vertical bars are connected to the machines and 
circuits. Each of the bars is broken in three places, and the machine may 
be connected to its circuit by plugging across these breaks, thus making 
the bar continuous ; by removing any pair of plugs the machine may be 
disconnected. 

Cll, Ell and Gil are ammeter jacks, and are used in connection with two 
plugs connected with a twin cable, for placing an ammeter in the circuit. 
The six horizontal bars are for the purpose of transferring a machine or 
a feeder to some circuit other than its own. Each horizontal bar is pro- 
vided, at one side of the panel, with a socket (A3, A4, A5, A7, A8, and A9) 
by means of which it can be connected with the horizontal bar on the 
adjoining panel. All ordinary combinations can be made by means of the 
bars and plugs ; but cable plugs are provided with each panel, so that when 
necessary, machines and feeders can be transferred without the use of the 
bar. These plugs and cables are intended for use only in case of an 
emergency. 

To run machine No. 1 on feeder No. 1, insert plugs in BIO, CIO, B6, C6, 



SWITCHING DEVICES. 



593 



B2, and C2. To shut down machine No. 2, and run feeders Nos. 1 and 2 in 
series on machine No. 1, insert a plug at C5, D5, C7, and D7, and remove 
plugs at C6 and D6 ; this leaves two circuits and two machines in series. 




a__fl 






1 



www feS=^ 




Fig. 9. 

Short circuit machine No. 2 by inserting the plug at E7. Cut out machine 
No. 2 by removing the plug at D10 and E10. Take out plug at D7. 



MWIKHIAO DEVICES. 

Switching devices in connection with switchboards can be divided gener- 
ally into two classes, viz. : 

1. Switches. 

2. Automatic circuit breakers. 



594 



SWITCHBOARDS. 




Tig. 10. Gen. Elec. Oil Break Switch, 5000 volts, 300 amns 
Opened and Closed by Hand. 




CASE REMOVED 



Fig. 11. Gen. Elec. Co. Oil Break Switch Opened and Closed by Hand 



SWITCHBOARD DEVICES. 



595 



Switches for low voltage and small current are of the same general form, 
though differing in details. In the main they consist of a blade of copper 
hinged at one end between two parallel clips, the other end of blade sliding 
into and out of two parallel clips. The clips are joined to copper or brass 
blocks to which the circuit is connected. 

There seems to be little uniformity among manufacturers regarding 
the cross-section of metal and surface of contact to be used. Perhaps a 




cross-section of metal of one square inch per 1000 amperes of current 
capacity is as near to the common practice as any, and a contact surface of 
at least one inch per 100 amperes or ten times the cross-section of metal is 
also common practice, but will depend somewhat on the pressure between 
surfaces. 

Auxiliary breaks are demanded by the National Code for currents 
exceeding 100 amperes at 300 volts, and "quick-break" switches are now 
quite common for pressure as low as 110 volts, although not in any way more 
necessary for that pressure than should be " quick-make" switches. 



596 



SWITCHBOARDS. 






The rules on switch design issued by the National Code cover the require- 
ments well, and they must be followed in order to obtain or retain low 
insurance rates ; all switches must meet the requirements. See index for 
" National Code," and refer to section on " Switches." 

Blades, jaws, and contacts should be so constructed as to give an even 
and uniform pressure all over the surface, and no part of the surfaces in 
contact should cut, grind, or bind when the blade is moved. The workman- 
ship should be such that the blade can be moved with a perfectly uniform 
motion and pressure, and the clips and jaws should be retained so perfectly 
in line that the blades will enter without the slightest stoppage. 

For pressures above 1000 volts, practice varies among the different manu- 
facturers. The General Electric Company makes a switch in which the cir- 
cuit is ruptured in oil. In the type designed by the Westinghouse Co. de- 
pendence is placed upon the arc being ruptured in open air by drawing 
it through a wide break. The Stanlay Co. has devised a switch which is 
designed to rupture the arc by means of a sliding shutter, which intercepts 
the arc when the contact is broken. 

For non-inductive loads of small power and up to 2500 volts, any good 
form of quick-break switch can be satisfactorily used. 

Two types of high-potential switches are shown on pages 594 and 595. 

AUTOMATIC CIRCUIT BREAKER!. 

Automatic circuit breakers are devices which have as an integral part 
an automatic trip which opens the circuit when the flow of current exceeds 





AMPERES 


A 


B 


C 


D 


E 


1800-3000 


24 


" ; S 


2 




l-K 


2000-6000 


28 




2 


'"i 


3% 


2000-10000 


30 


2S 


,U 


r ''h 


*H 



Fig. 13. One Form of Circuit Breaker. 1800 to 10000 Amperes. G. E. Co. 

a predetermined limit. Many types are now made, some with carbon sec- 
ondary breaks ; but a very successful type is one early introduced by the 
G. E. Co., with the magnetic blow-out principle applied to extinguish the 
arc. Illustrations follow of one of the main sizes and a table for the vari- 
ous adjustments of the same. 

For mean high potential circuits the Westinghouse Electric & Mfg. Cd. 
has devised the instrument shown in the folloAving cuts and diagrams (Figs. 
15 and 16) : — 

The circuit-breaker consists of two hardwood poles, one being longer 
than the other, mounted upon a marble base, to which are secured the 
terminals to which the main leads or wires are connected. The poles are 
connected by a hinge, so that their extremities are in line at the upper end. 
On the upper end of each pole is mounted a copper sleeve supporting a round 
carbon contact block with a hole through its center. The longer pole is 
provided with spring jaws or clips so that it may be quickly and easily 
attached to, or detached from, the terminals on the marble base. The short 
pole has a flexible wire running through its interior ; this wire is connected 
to the copper sleeve at the upper end of the short pole and to the lower clip 
terminal on the long pole. The sleeve at the upper end of the lung pole is 



AUTOMATIC CIRCUIT BREAKERS. 



597 




Amperes. 


Wide Open. 


Closed. 


When Sec. 

Contacts 

Touch. 


A 

i 


B 

i 


c 

1 


D 


E 


F 


D 


150- 2000 
1800- 3000 


ftof 


i 3 s 


§ 


I 7 B tO \ 


n 




|to| 


1 


2000- 6000 


§ 


A 


1 

4 


i* 


- 


ftoi 


1 


2000-10000 


§ 


A 


i§ 


|to| 


1 



Note — B is dimension when parts are new. 
First, Adjust E. 
Second, Adjust Brush Tension. 
Third, Adjust C 
Fig. 14. Dimensions for Adjusting MK Circuit Breakers. 

connected to the upper clip terminal. Thus, these connections practically 
make the sleeves at the upper ends of the two poles the terminals of the 
apparatus. 

The poles being removed from the base, a wire is inserted through the 
hole in the carbon tip at the upper end of the short pole, and secured to the 

Kigli Potential Circuit Breakers i?Ia«le tty Westing-house 
.Electric and manufacturing- Company. 




Fig. 15. 6000 to 15000 Volts. 



Fig. 16. 20000 to 40000 Volts. 



copper sleeve by a screw and washer. The other end of the fuse is passed 
through the carbon tip on the long pole, and secured to the copper sleeve by 
a cam-shaped lock. The length of the fuse should be from 6 to 10 inches. 

The poles, after being fused, are placed in position by taking hold of the 
lower end of the long pole. When the fuse blows, the short pole is released 
by the action of the spring at the lower end, and falls away from the station- 



598 



SWITCHBOARDS. 



Hig-h Potential Circuit Breakers, Hade by Westing-house 
Electric and. Manufacturing: Company. 








<V/ t > 


>ik 


» 


£. 


Wg 








1 








r 'P^ 










J* 







\ PRINCIPAL DIMENSIONS, 
6000-15000 VOLTS 

Figs. 17 and IS. 







PRINCIPAL DIMENSIONS', 
20000-40000 VOLTS 

Figs. 19 and 20. 



ary pole, thus making a very long break. The lock cam has a long string 
attached to it, by means of which the fuse can be released if desired, thus 
causing the short pole to drop in the same manner as when the fuse blows. 
This feature permits the device to be used as a switch. 



REVERSE CtRREKI CIRCUIT BBEAKERi. 

For large installations of electrical transmission, where it is highly im- 
portant that continuity of service shall be maintained, it is good engineering 
to use two separate lines of conductors. In such cases it is usual to keep 
both circuits connected so that in case of trouble on one of them its fuses or 
circuit breaking devices will cut it out, leaving the clear line to carry the 
load. An examination of the following diagram will explain the utility of 
the reverse current circuit breaker. Let a and a, be circuit breakers at the 
dynamo end of the two lines, and b and b x reverse current circuit breakers 
at the far end of the same. Should a short circuit occur as at x on the 
main line, it is plain that current will rush in both directions from the 
dynamo, by way of the main line and by way of the auxiliary line and the far 
end of the main line, in which portion the direction of the current will 
be the reverse of what it was ordinarily. Under this condition it is obvious 
that all the circuit opening devices would opei'ate, and the auxiliary line 
would be of no effect in maintaining continuity of current. Now, if circuit 
breakers of such a design that they will open on a reversal of the direction 



REVERSE CURRENT CIRCUIT BREAKERS. 



599 




--*- ; & 



AUXILIARY LINE 



a 



&U, BUFFALO 

tr 

Fig. 21. Diagram Showing Use of Reverse Current Circuit Breaker. 

of the current through them, be placed at the far end, as at b and b t then the 
main circuit breakers, a, a, will open, as will also the reverse current circuit 
breakers, b, b, thus leaving the auxiliary line intact. Of course a short 
circuit on the auxiliary line will operate in a similar manner. 

The following diagram shows the connections of the reverse current 
circuit breaker at Buffalo as designed by the General Electric Co. An 




vvirvvyvw POTENTIAL- vvvvvvvvv 

wwww\ i yvwwwv 

■ 1 < — 1 1 — ' ' I 



CIRCUIT BREAKERS 





Pig. 22. The Circuits of a Reverse 
Current Circuit Breaker Set 
Showing How a Direct Current 
Motor is Used with Alternating 
Currents to Distinguish between 
Power Passing in One Direction 
and Power Passing in the Other 
Direction in the Line. 



Fig. 23. The Circuits of a Time 
Element Relay Circuit-break- 
ing Set. 



600 SWITCHBOARDS. 



ordinary fan motor is introduced by means of a transformer into the line, 
and acts to operate a relay on the shunted circuit breaker, a reversal of the 
current reversing the motion (or pull) of the fan motor armature, and closes 
the relay contacts as shown. 

TiiiK* Ulement for Circuit Breaker.ii. — Where circuits are loaded 
with large synchronous or induction motors and other devices liable to 
produce short circuits on the system when out of step or started too sud- 
denly, it is not only necessary to protect the local or feeder circuit with 
circuit breakers, but in order to prevent the operation of all the protecting 
devices between the one in trouble and the dynamo itself, it is found advis- 
able to introduce a time element or adjustable delay on all the main circuit 
breakers. This device must allow the circuit breakers farthest from the 
station to be adjusted so they will open first, and all the intermediate 
devices must have variable or graduated adjustments, say for opening after 
three seconds, and the main circuit breaker at the power house itself will 
open last of all, say in five seconds. 

Mr. L. B. Stillwell devised an instrument for this purpose, and it has been 
widely adopted. Both the Westinghouse Co. and General Electric Co. have 
adapted this time element device to the circuit breakers in use at Niagara 
Falls, and cut No. 23 shows the arrangement by General Electric Co. dia- 
gramatically. The instrument is composed of a simple clock movement, 
the wheels of which are prevented from turning by a pawl which may be 
lifted out of place by either one of two relay magnets connected by trans- 
former in the main line. The lifting of the pawl allows the clock wheels 
to revolve and close a relay circuit connected with the circuit breakers 
which promptly open. The clock movement can be adjusted to close the 
local circuit in any desired time ; and in case the clock is started on a short 
circuit, which is off before the lapsing of the time period, the pawl drops, 
and the movement returns to its original position. 



LIGHTNING ARRESTERS. 



IIGHTWI^G AAREMTERK Il¥ ©EXER.-iL, 

(From pamphlet by Westinghouse Electric & Manufacturing Company.) 

Xlie Tunctiom of liig-litiiing- Arresters. — The function of a 
lightning arrester is two-fold. It should provide a path to earth offering 
the least possible resistance to the passage of static discharges, and it 
should avoid interruption of the service. The latter, though a negative 
function, is one of primary importance. 

In the early days of electrical industry it was found that lightning dis- 
charges from overhead wires would pass more readily to ground over a 
small air gap than through coils or even long lengths of straight wire. 

Numerous arresters based upon this principle were constructed and 
placed in practical use. The simplest form of these is the old saw-tooth 
spark-gap arrester which is still used for protecting telegraph and telephone 
lines. But a great difficulty arose with gap arresters when used on electric 
lighting, railway or power circuits, owing to the fact that the dynamo cur- 
rent followed the lightning discharge, establishing thereby a short circuit 
which would melt the dynamo fuses and thus interrupt the service. 

With the object of overcoming this trouble various arresters were de- 
vised that would automatically interrupt the dynamo short circuit. At 
first this interruption was accomplished by simply placing fuses in the 
lightning arrester circuit, thus making it necessary to renew the fuses after 
each discharge. This method was obviously unsatisfactory. Arresters 
were then devised which would automatically interrupt the arc and then 
immediately adjust themselves for another discharge by means of moving 
parts ; the latter, however, proved to be the cause of considerable annoy- 
ance, and experience demonstrated that the arc rupturing arresters were 
uncertain in action and hence unreliable. 

Recognizing the importance of the problem the Westinghouse Electric 
& Manufacturing Company undertook a series of extensive theoretical and 
practical investigations, with the object of devising arresters which would 
offer a low resistance path to ground for disruptive discharges, and at the 
same time operate automatically and repeatedly without moving parts and 
without interrupting the service. 



1000 'VO'CTS 
DYNAMO 



2000 VOLTS 



3000 VOLTS 



STATION 
ARRESTER 



GROUND 
LINE LINE 




Fig. 1. Diagram Showing Electrical Connections for A. C. Lightning 

Arresters. 

The results of these investigations, which extended over a period of sev- 
eral years, are embodied in the Wurts Non-arcing Lightning Arresters. 

With a non-arcing arrester the dynamo current does not continue to fol- 
low the discharge ; the apparatus is not left unprotected for an instant ; 
the instrument does not deteriorate ; it is entirely automatic in action, and 
will handle frequent and persistent discharges with perfect facility. 

For systems of distribution, with their various motors, converters, and 
other appliances, a liberal allowance of line arresters judiciously distributed 
over the lines is essential for securing adequate protection. Much, how- 

601 



602 



LIGHTNING ARRESTERS. 



ever, depends upon the local conditions, such as the character of the soil 
with reference to the ground connections, and severity of lightning dis- 
turbances, the grade of insulation to be protected, the voltage of the circuit 
and the surroundings with reference to telegraph and telephone wires. 




Fig. 2. Double-Pole Non- Arcing Metal Lightning Arrester. Type " A. 
(For Station Use.) 




FlG. 3. Unit Lightning Arrester, Type " C," Showing Cylinders in Place. 
THE KOX>ARCIH6 METAI J.IOHTHTOTC* 

The non-arcing metal lightning arrester for alternating current circuits is 
based upon the discovery made by Mr. A. J. Wurts that an alternating 
current arc cannot be maintained over a short air-gap when the electrodes 
consist of certain metals and alloys thereof. Types " A " and " C " arresters, 
described below, are of the non-arcing metal type, 



THE NON-ARCING METAL LIGHTNING ARRESTER. 603 



Tlie Type "A" Arrester. — The construction of this arrester can 
he best understood by reference to Fig. 2. 

It will be noted that there are seven independent cylinders of non-arcing 
metal placed side by side and separated by air-gaps. The cylinders, which 
are mounted on a marble base, are knurled, thus presenting hundreds of 
confronting points for the discharge. The dynamo terminals are connected 




Figs. 4, 5. Double-Pole Non-Arcing Metal Line Arrester — Type " C." 



to the end cylinders, and the middle cylinder is connected to the ground. 
The arrester is, therefore, double pole, that is, one arrester protects both 
sides of the circuit. When the lines become statically charged the dis- 
charge spark passes across between the cylinders from the line terminals to 
the ground. The non-arcing metal will not sustain an arc or become fused 
by it ; hence with an arrester constructed of this material all possibility of 
vicious arcing and short circuits is avoided. There are no moving parts, 
no coils to impede the passage of the lightning discharge, and in fact 
nothing that requires either adjustment or inspection. These arresters are 
made in units for 1000 volts ; for 2000 volts two units are connected in 
series, and for 3000 volts three are connected in series, all as indicated in 
the diagram, Fig. 7. 




Fig. 6. Lightning Arrester for 15,000 Volt Circuit — Type " R. 



604 



LIGHTNING ARRESTERS. 



The Type " C " Arrester. — This is similar to type " A," but instead 
of being mounted on marble it is inclosed in a weather-proof iron case for 
line use. The cylinders are placed in porcelain holders, as shown in Figs. 3 
and 4. The arrester complete in the iron case is shown in Fig. 5. The 
method of connecting type " C " arresters to circuits of different voltage is 
also shown in Fig. 1. 

The Type " H, " Arrester. — A standard form of arresters for pro- 
tecting alternating current high potential power transmission circuits is 
shown in Fig. 6. A diagram illustrating the method of connecting the 
arresters and choke coils for various voltages is given in Fig. 7. 



FK. 1 

DYN. LINE 

8,000 VOLT8 


Fig. 2 

DYN. LINE 
5,000 V0LT8 4=r 


Fig. 5 
DYN. LINE 

OtOtOtOtO^V 

Y Y Y 




V 


5 

15.000 VOLTS 


Fig. 3 

DYN. LINE 


Fig. 4 

DYN. LINE 


| 

8,000 VOLTS 


i 

10,000' VOLTS 



Fig. 7. Diagram Showing Pyramidal Form of Connecting Lightning 
Arresters and Choke Coils for Various Voltages. 

Explanatory Note — Each circle represents a choke coil. Each rect- 
angle represents one unit (type " C ") non-arcing metal lightning arrester. 



CHOKE COILS FOR A. C. CIRCUITS. 



605 



Sub-Fig. 1, four coils in series and one and one-half unit arresters between 
line and ground. Sub-Fig. 2, five coils in series and two and one-half unit 
arresters between line and ground. Sub-Fig. 3, six coils in series and four 
unit arresters between line and ground. Sub-Fig. 4, six coils in series and 
five unit arresters between line and ground. Sub-Fig. 5, six coils in series 
and seven unit arresters between line and ground. 



3,eoo vouxs 




8,000 VOLTS 



FlG. 8. Plan View of Lightning Arrester Racks, Showing Unit Lightning 
Arresters and the Connections for Each Voltage. 



CHOKE COIJLS V OR A.. C. CIRCUITS. 



A lightning discharge is of an oscillatory character and possesses the 
property of self-induction ; it consequently passes with difficulty through 
coils of wire. Moreover, the frequency of oscillation of a lightning dis- 
charge being much greater than that of commercial alternating currents, a 
coil can readily be constructed which will offer a relatively high resistance 
to the passage of lightning and at the same time allow free passage to all 
ordinary electric currents. 

Any coil will afford a certain amount of impedance to a disruptive dis- 
charge. Experience has shown, however, that there is one form which 
offers at once the maximum impedance to the discharge with the minimum 
resistance to the generator current. 

Choke coils of this type connected in the circuit, when used in connec- 
tion with non-arcing lightning arresters, offer a very reliable means of pro- 
tecting well-insulated apparatus against lightning. This arrangement is 
particularly suited for protecting station apparatus in power transmission 
systems. Coils can, however, be used to advantage on the line for the pro- 
tection of the more expensive translating devices. 



606 



LIGHTNING ARRESTERS. 



Tests made under actual working conditions indicate that for ordinary 
commercial voltages effective protection is obtained with four choke coils 
in series in each wire, with four lightning arresters intervening, as shown 
in Fig. 10. This diagram also shows the' method of connecting the coils and 
arresters to one end of a three- wire transmission system. 




Fig. 9. A. C. Choke Coil. 




Fig. 10. One end of a 2000-Volt 3-Wire Power Transmission System 
Showing Bank of Choke Coils and Lightning Arresters. 



GROUND CONNECTIONS. 



607 



ABRISTEKi FOR B. C. CIRCUITS. 

The non-arcing metal arresters described above are not suitable for use 
on D. C. circuits, but a non-arcing D. C. arrester has been devised by Mr. 
A. J. Wurts. 

The principles upon which this arrester is designed are based upon the 
following facts : — 

First. A discharge will pass over a non-conducting surface, such as 
glass or wood, more readily than through an equal air-gap. 

Second. The discharge will take place still more readily if a pencil or 
carbon mark be drawn over the non-conducting surface. 

Third. In order to maintain a dynamo arc "fumes or vapors of the elec- 
trodes must be present ; consequently if means are provided to prevent the 
formation of these vapors there will be no arc. 




of 


r-g 


e 




ff 




> 




• 

o 


o 
e 

fill 

o 


• 

o 






• 


• 
o 


• 






0© 


i 


M 


N 




<s> <s> 




FlG. 11. Non-Arcing Railway Lightning Arrester, Type 

(For Station Use.) 



The Type "It" Arrester. — The illustration, Fig. 11, shows the 
type " K " arrester for station use on D. C. circuits up to 700 volts. The 
instrument is single pole, and consists of two metal electrodes mounted 
upon a lignum-vitse block, flush with its surface. Charred or carbonized 
grooves provide a ready path for the discharge. A second lignum-vitse 
block fits closely upon the first block, completely covering the grooves and 
electrodes. Disruptive discharges will pass readily between the electrodes 
over the charred grooves, which act simply as an electrical crack through 
the air, providing an easy path. 

The resistance between the electrodes is more than 50,000 ohms, so that 
there is, of course, no current leakage, but it should not be understood that 
the lightning discharge passes through this high resistance — it leaps over 
the surface of the charred grooves from one electrode to the other exactly 
as it would if there were but a simple air-gap. The presence of the charred 
grooves simply makes the path easier. 

There being no room for vapor between the two tightly fitting blocks, no 
arc can be formed, hence the arrester is non-arcing. 



grouhtij coi¥arECTio]¥S for a. c. ajjtd ». c. 
hires:*! i:it*. 

Too much importance cannot be attached to the making of proper con- 
nections from the arrester to ground, which should be as short and straight 
as possible. 

It is obvious that a poor ground connection will render inefficient every 



608 



LIGHTNING ARRESTEES. 



effort made with choke coils and lightning arresters to drive the static elec- 
tricity into the earth. It is, therefore, important that we not only should 
understand how to construct a good ground connection, but also thoroughly 
appreciate the necessity of avoiding unfavorable natural conditions. 

A good ground connection for a bank of station lightning arresters may 
be made in the following manner : First, dig a hole six feet square directly 
under the arrester until permanently damp earth has been reached ; second, 
cover the bottom of this hole with two feet of crushed coke or charcoal 
(about pea size) ; third, over this lay 25 square feet of No. 16 tinned copper 
plate ; fourth, solder the ground wire, preferably No. copper, securely 
across the entire surface of the ground plate ; fifth, cover the ground plate 
with two feet of crushed coke or charcoal ; and sixth, fill in the hole with 
earth, using running water to settle. 

The above method of making a ground connection is simple, and has 
been found to give excellent results, and yet, if not made in proper soil, it 
would prove of little value. Where a mountain stream is conveniently near, 
it is not uncommon to throw the ground plate into the bed of the stream. 
This, however, makes a poor ground connection, owing to the high resist- 
ance of the pure water and the rocky bottom of the stream. Clay, even 
when wet, rock sand, gravel, dry earth and pure water are not suitable 
materials in which to bury the ground plate of a bank of lightning arresters. 
Rich soil is the best. It is therefore advisable before installing a bank of 
choke coils and lightning arresters to select the best possible site for the 
lightning arrester installation, with reference to a good ground connection. 
This may often be at some little distance from the station, in which case it 
is of course necessary to construct a lightning arrester house. Where per- 
manent dampness cannot be reached, it is recommended that water be sup- 
plied to the ground through a pipe from some convenient source. 

LI^HTXIXCk arresters for direct current. 

(From pamphlet by General Electric Company.) 

Some years ago Prof. Elihu Thomson devised a lightning arrester based 
on the principle that an electric arc may be repelled by a magnetic field. 
In this device, the air-gap, across which the lightning discharges to reach 




Fig. 12. Type 



Arc Station Arrester. 



the ground, is placed in the field of a strong electro-magnet. When the 
generator current attempts to follow the high potential discharge, it is 
instantly repelled to a position on the diverging contacts Avhere it cannot be 
maintained by the generator, 



LIGHTNING ARRESTERS FOR DIRECT CURRENT. 609 



The magnetic blow-out principle has been employed in the construction 
of a complete line of lightning arresters for all direct current installations, 
and in more than ten years of service magnetic blow-out arresters have 
always been effective in affording protection to electrical apparatus. 

In designing lightning arresters for the protection of high-voltage alter- 
nating current circuits, however, different conditions have to be met, since 
high-voltage arcs are not readily extinguished by a magnetic blow-out. In 
a recently designed lightning arrester for alternating current circuits, 
metallic cylinders with large radiating surfaces are found to so lower the 
temperature of the arc that volatilization of the metal ceases and the arc is 
extinguished. 




Fig. 13. Type "AA" Arc Station Arrester. 

The variety of these lightning arresters provides for the protection of all 
forms of electrical apparatus and circuits. 

The Type "A" Arrester is manufactured for the protection of arc lighting 
circuits, and is in extensive use throughout the world. Its construction 
includes a pair of diverging terminals mounted on a slate base with an 
electro-magnet connected in series with the line. The magnet windings are 




Fig. 



14. Type "A," Form " C," Lightning Arrester, 
in Iron Box for Line Use 



610 



LIGHTNING ARRESTERS. 



of low resistance, and therefore consume an inappreciable amount of energy 
with the small current used for arc lighting, although they are always in 
circuit. 

The single Type "A" Arrester is suitable for circuits of any number of 
series arc lamps not exceeding seventy-live. For circuits of higher voltage, 
a double arrester known as the type '-AA" is made by mounting two 
arresters on one base and connecting them in series. One arrester should 
be installed on each side of the circuit, as shown in the Diagram of Con- 
nections. 

For use in places exposed to weather, the Type 'A" Arrester is furnished 
inclosed in an iron case, and designated Type 'A," Form " C." 




FlG. 15. Connections for Type 

"A" Arresters. 



Fig. 16. Type " B " Incandescent 
Station Arrester 300 Volts or Less. 



The construction of the Type " B " Arrester is similar to that of the Type 
"A," but its magnet windings are excited only when a discharge takes place 
across the air-gap. A supplementary gap is provided in the Type " B " 
Arrester, in shunt with the magnets, thus providing a relief for the coils 
from excessive static charge without affecting their action upon the main 
gap. The magnet coils, carrying current only momentarily, allow the same 
arrester to be used on circuits of large and small ampere capacity. The 
Type "B" can also be furnished with weatherproof case similar to that 
used with Type "A." 




Fig. 17. Type "MD" for Direct 
CurrentCircuits up to 850 Volts. 



Fig. 18. Connections for 
Type " B " Arresters. 



LIGHTNING ARRESTERS FOR DIRECT CURRENT. 611 



The Type " MD" Lightning Arrester has been designed for use on direct 
current circuits up to 850 volts. While similar to Type"M," Form " C " 
Arrester, it is considerably smaller, and is inclosed in a compact porcelain 
box measuring 7£ inches x 5 inches x 4£ inches. For street car and line use, 




Fig. 19. 



MD " Lightning Arrester in Wood Box. 



the arrester is furnished in an additional box of iron or wood, as shown by 
Fig. 19. 

This arrester has been adopted as standard for railway and all direct 
current 500-volt circuits. It has a short spark gap, a magnetic blow-out, 
and a non-inductive resistance. 

CONNECTIONS OF 

MAGNETIC BLOW-OUT LIGHTNING ARRESTERS TYPE MD. 

FOR DIRECT CURRENT CIRCUITS UP TO 850 VOLTS. 



CONNECTIONS FOR LIGHTING OR POWER CIRCUITS. 
(METALIC CIRCBITS) 



REACTANCE COIL 




GROUND 

STATIONS ARRESTERS 




^= GROUND 
CAR AND LINE ARRESTERS 



CONNECTIONS FOR RAILWAV 
CIRCUIT 
(ONE SIDE GROUNDED) 



25 FT. OF CONDUCTOR WOUND IN A 

COIL OF TWO OR MORE TURNS 

AS CONVENIENT. 



^^ GROUND 




Fig. 20. Connections of Magnetic Blow-out Lightning Arresters, 
Type " MD " for Direct Current Circuits up to 850 Volts. 



612 



LIGHTNING ARRESTERS. 



LKkITTXIXC; ARREiTERi FUR AL!TKiniTII\«p 
CURRElfX. 

Tlie G. E. Alternating Current Arresters have been designed to operate 
properly with very small gap spaces. The arrester for 1000-volt circuits has 
two metal cylinders 2 inches in diameter and 2 inches long, separated by a 
spark gap of about ^ inch. One cylinder is connected to the overhead 
line and the other cylinder to the ground, and a low non-inductive graphite 
resistance is placed in circuit. The large radiating surface of the metal 
cylinders combined with the effect of the non-inductive resistance prevents 
heating at the time the lightning discharge passes across the gap, and the 
formation of vapor which enables the current to maintain an arc is thus 
avoided. 





/ '/////A// GROUND 



5000 V. ARRESTER CONSISTS OF TWO 2000*V.- 7500 V. ARRESTER CONSISTS OF THREE 2000 V. 
D. P. ARRESTERS CONNECTED IN SERIES'. D. P. ARRESTERS CONNECTED IN SERIES. 



ALTERNATOR 





10000 V. ARRESTER CONSISTS OF FOUR 2000 V. 
D.P. ARRESTERS CONNECTED IN SERIES. 



15000 V. ARRESTER CONSISTS OF SIX 2000 V. 
D.P. ARRESTERS CONNECTED IN SERIES. 

FIG. 21. Connections of Wirt or G. E. Alternating Current Short Gap 
Lightning Arresters, 5000 to 15,000 volts. 

The arrester under normal action shows a small arc about as large as a 
pin-head between the cylinders. 

The arrester for 2000-volt circuits is designed with two gaps of approxi- 
mately ^3 inch each and a low non-inductive resistance. 

The G."E. Arresters are now furnished by the General Electric Company 
for use on all alternating current circuits at practically any potential. For 
circuits above 2000 volts, the standard 2000-volt double-pole arrester has 
been adopted as a unit, and several of these are connected in series to give 
the necessary number of spark gaps. 



LIGHTNING ARRESTEES FOR ALTERNATING CURRENT. (513 

1 




FlG.22. G. E. Alternating Current 
Lightning Arresters. 





Fig. 23. 



2000 V.D. P. ARRESTERS CONNECTED 
AS 3000 V.S. P. ARRESTERS. 

ALTERNATOR 



Fig. 24. Connections of Wirt 
or G. E. Alternating Current 
Short Gap Lightning Arresters, 
1000 to 3000 Volts. 



ALTERNATOR 




GROUND 
1000 V.S. P. 1000 V.D. P., 



GROUND 
2000 V.S..P. 2000 V.D. P. 



614 



LIGHTNING ARRESTERS. 



THE OARTOI ARREiTEB. 



In Fig. 25 a cross-section view is shown of the 
Garton Arrester. 

The discharge enters the Arrester by the bind- 
ing post A, thence across non-inductive resistance 
B, which is in multiple with the coil F, through 
conductors imbedded in the base of the Arrester, 
to flexible cord C, to guide rod D and armature 
E, which is normally in contact with and rest- 
ing upon carbon H, thence across the air-gap to 
lower carbon J, which is held in position by 
bracket K. This bracket also forms the ground 
connection through which the discharge reaches 
the earth. 

We have noted that the discharge took its 
path through the non-inductive resistance in 
multiple with the coil. This path is, however, 
of high ohmic resistance, and tbe normal cur- 
rent is shunted through the coil F, which is 
thereby energized, drawing the iron armature 
E upward instantly. This forms an arc between 
the lower end of the armature and the upper 
carbon H. As this arc is formed inside the 
tube G, which is practically air-tight, the oxygen 
is consumed, the current ceases, and the coil 
loses its power, allowing the armature to drop 
of its own Aveight to its normal position on 
the upper carbon. The arrester is again ready for another discharge. 

Tlie £». K. C. JLig-htning- JLrrester Equipment, manufactured by 
the Stanley Electric Mfg. Company of Pittslield, Mass., consists of tbree 
essential parts. The Lightning Arrester proper is two nests of concentric 
cylinders, with diverging ends held in relative position by porcelain caps, as 
shown in cross-section Fig. 26. To the innermost cylinder the line is con- 
nected ; to the outer, the earth. The porcelain caps are provided with 




Fig. 25. 



»: 




FIG. 1 

•" 'VERTICAL.SECTION OF 
UGHTNING ARRESTER 



Fig. 26. 




Fig. 27. 



grooves so placed as to make all spark gaps one-sixteenth inch wide. Be- 
tween these grooves are sufficient perforations to allow the free circulation 
of air between the cylinders. If, on the occasion of lightning, the dynamo 
current follows the lightning, a current of air is at once established through 
the perforations between the cyclinders, blowing the arc between the flar- 
ing ends Avhere it is instantly ruptured. 

Between the line terminal and the ground connection there are three 
spark gaps, each one-sixteenth inch in width, making a total of three-six- 



THE UARTON ARRESTER. 



614a 



teenth inch air-gap between either line-wire and the ground. At ordinary 
frequencies five thousand volts or over are required to jump the gaps of the 
arrester ; but at the frequency of a lightning discharge the sparking poten- 
tial is reduced to less than one-half of this. This phenomenon shows that 
the relative value of spark gaps cannot be expressed by " short " and 
" long," and their effectiveness as lightning protection cannot be measured 
by inches. 

The spark gaps of the arrester described are about double the widths 
ordinarily used, yet the sparking potential at lightning frequencies is less. 
The concentric cylinders provide large discharge surface, enabling the 
arrester to take care of all the heavy discharges, relieving the line com- 
pletely. 

The second essential feature of the S. K. C. Lightning Arrester Equipment 
is a Choke Coil, so wound (Fig. 27) as to possess great opposition to the 
passage of lightning, yet practically no self-induction with currents of ordi- 
nary frequency. This coil is to be* placed in the circuit between the light- 
ning arrester and the apparatus to be protected. Introducing such a coil 
between the lightning arrester and the machine will offer practically no 
disturbing effect, either as to magnitude of the output or regulation of the 
system, and at the same time interposes 
enormous opposition to the passage of light- 
ning discharges towards the machine to be 
protected. 

To remove even the slightest static dis- 
charge from the line, an instrument similar 
to the one illustrated in Fig. 28, called a 
" Line Discharger," when used with the ap- 
paratus above described, discharges the line 
completely. The S. K. C. Line Discharger 
is a minute air-gap in series with a tube or 
tubes, filled with oxidized metallic particles, 
thus offering practically an infinite resis- 
tance to dynamic currents, yet allowing sta- 
tic discharges of extremely low potential to 
readily pass to earth. The Line Discharger 
is connected to the line as shown in Fig. 29. 
The number of tubes required is determined 

by the voltage. As the Line Discharger will remove even the small static 
charge, it prevents the accumulation of such charges on the line which might 
prove dangerous. 





.LilUbridge,.2ir23i 



GROUND 

LIGHTNING PROTECTION 

FOR 

5000 VOLT TRANSMISSION LINE 

USING 

s.k.c. arresters, choke coils and 
line discharges 

Fig. 29. 



1 



ELECTRICITY METERS. 



Meters for measuring the amount of electrical energy furnished to cus- 
tomers are commercially called wattmeters or recording wattmeters, 
whereas they are really measurers or meters of watt-hours. The Edison 
chemical meter, in which a shunted definite portion of the current supplied 
to the customer is made to deposit zinc upon an electrode of an electrolytic 
cell, is properly a coulomb meter, or ampere hour meter, which becomes a 
watt-hour meter if the pressure be maintained constant. 

This last meter is rapidly going out of use. The Thomson watt-hour 
meter, which is replacing it, can be used upon either direct or alternating 
circuits. It consists of a motor whose armature is connected in series with 
a resistance to the two mains, and whose field coils are in series with the 
supply circuit. The armature in rotating moves a recording mechanism. 
The rapidity of rotation is regulated by a copper disk connected to the 
armature shaft and moving between the poles of adjustable permanent 
magnets. It is made for use on two or three wire circuits, arc circuits, 
single phase or three phase a. c. circuits, and for recording input and output 
of storage batteries. The following diagrams show some of the principal 
uses to which it is put with the scheme of the connections to the circuits. 
There are many other purposes to which it is put, but the reader is referred 
to the instruction books accompanying the meters for further information 
on the subject. 




Fig. 1. Two-wire Meter. 
(Small Capacity.) 



615 



Fig. 2. Two-wire Meter. 
(Large Capacity.) 



616 



ELECTKICITY METERS. 




FlG. 3. Three-wire Meter. (High 
Efficiency Type). 





Fig. 4. Primary Meter. 




Fig. 5. Arc Circuit Meter. 



Fig. 6. Station Arc Meter. 



ELECTRICITY METERS. 



6V> 




Fig. 7. Balanced Three-phase Secondary Meter. 




Fig. 8. Balanced Three-phase Primary Meter. 



618 



ELECTRICITY METERS. 





Fig. 9. Two-wire Meters from. 
75 Amperes to 1200 Amperes. 



Fig. 10. Two Meters on Mont 
cyclic System. 



a anm 




Fig. 11. Balanced Three-phase 
Meter. 




Fig. 12. Three-wire High 
Efficiency Meter. 



TUBE RESISTANCE 





Fig. 13. Arc Circuit Meter. Fig. 14. Single-phase Primary Meter 



ELECTRICITY METERS. 



(519 







\ 


















CASE RESISTANCE 




















f GENERATOR 



Fig. 15. Large Capacity Station 
Meter Form G 2 . 



Fig. 16. Station Arc Meter. 




Fig. 16a. For Storage Battery 25 and 50 Amperes. 100 volts. 



GE\ER.4L KOTEi CONCERNXNCt THOMSOI 
IHElERi. 

In case a new jewel is inserted in the meter it is advisable to put in a 
mew shaft end, as the point on the old one will probably be injured, 
more particularly if the meter has been running on the broken jewel. 

Just before inserting a new jewel in a meter, it is well to place a drop of 
fine watch oil on the jewel. 

Oil must not we used, in the top bearing under any circumstances. 

Oil or dirt on the commutator will cause the meter to register less than 
the correct number of watt hours. 

If no " constant " is marked on the dial, the meter reads directly in watt 
hours. 

See that the disk and armature move freely, and that no dirt collects on 
the magnets in such a way as to touch the disk. 

Install the meter in a dry place, as far away from any heavy vibration as 
possible. 

When it is necessary to install a meter near a railroad, or in any place 
where the vibration is sufficient to cause sparking at the brushes, the ten- 
sion of the brushes upon the commutator should be slightly increased. This 
will do away with the sparking, and ensure greater accuracy. 

In case of severe jar, it is advantageous to place a number of soft rubber 
washers under the heads of the screws which bind the meter to the wall and 
between the meter and the wall itself at each screw. 

The disk will always rotate to the right when trie meter is properly 
connected. 



620 ELECTRICITY METERS. 



Testing- of Thomson Uncording- Wattmeters. 

Most companies find it desirable to test meters on their lines from time to 
time, not so much to check the accuracy of the meters as to he able to state 
to the customer how the meter is operating. If only a rough test be required, 
it can be made by turning on a specified number of lights, multiplying the 
number of lights by the average watts per lamp, and using the following 
standard formula : — 

3600 x Constant (if meter has one) „ , , _ „ ,. , 

, Tr ^ \ = Seconds per revolution of disk. 

Watts m use ^ 

By using a stop watch, meters can be tested in this way, and the only in- 
accuracy is the difference between the estimated and actual watts per lamp. 

If a more accurate test be required, there are two methods, both of which 
are simple, and obviate the necessity of taking down the meter. 

A portable indicating wattmeter may be connected in series with the 
meter to be measured. The portable instrument will read directly in watts, 
and with the above formula give an absolute test. 

Another method is to have half a dozen high candle-power lamps, which 
have been tested at the station so that their wattage at all voltages is abso- 
lutely known. These lamps can be connected as the only load on the meter. 
By reading the voltage at the point of test with a portable voltmeter, and 
noting the watts recorded by the meter for the group of lamps, a direct 
comparison can be made. 

Calibration of Thomson Recording* "Wattmeters. 

Meters which have been neglected, misused, or very much worn, should 
be taken down, and brought into the station for repair and recalibration. 
In modern meters the speed can be increased or retarded about 16% by 
moving the magnets. On older meters having only one movable magnet, 
the variation obtainable by moving the magnet is considerably less. Meters 
which cannot be properly calibrated by moving the magnets can be roughly 
corrected by changing the resistance in series with the armature. Meters 
which are slow on light loads can be speeded without affecting the accuracy 
on high loads by increasing the shunt field coil, which is the fine winding. 
Meters which show a tendency to creep, that is, to move slightly without 
any load, have too many turns in the shunt field coil. Creeping is almost 
invariably traceable to vibration, which aids the meter to overcome friction 
on very light loads. It can be corrected by removing turns from the shunt 
field coil until the meter disk just barely fails to move on no load. 

AITEHUATIIIfG CIRBEST METERS. 

In addition to the Thomson watt-hour meter, which is used on either a.c. 
or d.c. circuits there is a class of induction meters used only on the a.c. 
circuits. The Schallenberger meter is of this type, and is made by the 
Westinghouse Electric and Manufacturing Company in several designs, such 
as Watt-hour meters, ampere-hour meters, and the first mentioned are also 
made in two- and three-phase meters. 

All of these meters depend in some way on the rotating of a disk or cyl- 
inder by means of induction coils properly placed in relation thereto. 

The Duncan integrating meter is another of the class, and one formerly 
made by the Fort Wayne Electric Corporation was very similar to the 
Schallenberger ampere-hour meter. Some of these meters are regulated as 
to speed by small fans placed on the armature shaft, and are hardly as 
accurate as those having a retarding disk between magnets. 

THE STAHTIET METER. 

The Stanley manufacturing Company has recently (January, 1899) brought 
out an a.c. meter that is sealed and warranted to remain accurate within a 
very small percent for a period of 3 years, provided it is properly installed 
and the seals are not broken. This meter is of the induction type, and the 
disk upon which the coils act is held in suspension, and at the same time 
retarded by two permanent magnets. The disk is so adjusted as to remain 
suspended "midway between the poles of the magnets, and there is no other 
gearing for friction. 



THE STANLEY METER. 
The following two cuts show its construction : — 



621 





Figs. 17 and 18. 



Directions for Installing- Stanley Meters. 

Place the instrument on a secure support in as nearly a vertical position 
as can be judged by the eye. Open one of tbe mains in the circuit to be 
metered, and connect the heavy black terminal of the meter to the main 
leading to the transformer or current generator, and connect the white ter- 
minal toward the lamp circuit or current consuming device. Connect the 
small shunt wire directly across the mains to the opposite side of the circuit 
so that the shunt connection of the meter will receive the full working 
pressure of the circuit at approximately the voltage indicated on the case 
cover. See cuts No. 19 and No. 20 for diagrams of connections. 










o: 


w|f 


¥ 




efi 


L 




111 




i 



Figs. 19 and 20. 



Directions for Reading*. 

Kilo- watt hours are recorded directly on the dial without the use of a con- 
stant, unless otherwise marked on the case cover. The first right-hand 
pointer on the dial indicates 1,000 Watt hours, or 1 K. W. H. for one com- 
plete revolution of the pointer, and each unit indicated by this pointer rep- 
resents 100 Watt houi's. The other pointers, taken in order from right to 
left, record successively 10 K. W. H., 100 K. W. H., 1,000 K. W. H., and 
10,000 K. W. H. for one complete revolution of the pointer. 



622 



ELECTRICITY METERS. 



DIAGRAMS OF COHnVECTIOarS OF KHALLES. 

BERGER IITTEORATI^O WATTMETERI 
XO VARIOUS §IYL£§ Or CIRCUITS. 




Fig. 21. Connections for Single-Phase Circuits ; Current not exceeding 100 
Amperes, Potential not exceeding 500 Volts. 

The illustration above shows the method of connecting a meter to a single- 
phase circuit, carrying a current not exceeding 100 amperes and at a poten- 
tial not exceeding 500 volts. 




Pig. 22. Connections for Single-Phase Circuit ; Current exceeding 100 
Amperes, Potential not exceeding 500 Volts. 



The illustration herewith shows the method of connection to a single- 
phase circuit carrying a current exceeding 100 amperes at a potential not 
exceeding 500 volts. In this case a series transformer is used, the current 
to be measured passing through the primary coil of the transformer, while 
the meter receives from the secondary coil of the transformer current bear- 
ing a fixed ratio to the primary current. 



DIAGRAMS OF CONNECTIONS. 



623 




Fig. 



23. Connections for Single-Phase Circuit 
Volts. 



Potential exceeding 500 



The illustration shows the method of connecting the meter to a single- 
phase circuit carrying current at a potential exceeding 500 volts. To keep 
the high potential current out of the meter, both a series and a shunt trans- 
former are used, even for currents not exceeding 100 amperes. 




Fig. 24. 



Connections for Polyphase Circuits ; Current not exceeding 100 
Amperes, Potential not exceeding 500 Volts. 



The illustration above shows the method of connecting two meters to a 
three-wire polyphase circuit, in which the current traversing each of the out- 
side wires does not exceed 100 amperes, while the potential between either 
of the outside conductors and the middle conductor does not exceed 500 
volts. This connection is correct for a three-wire, two-phase system, and 
also for a three-wire three-phase system. 



624 



ELECTRICITY METERS. 




Fig. 25. Connections for Polyphase Circuits ; Current exceeding 100 
Amperes, Potential not exceeding 500 Volts. 



The illustration herewith shows the method of connecting two of these 
meters to a three-wire polyphase circuit, where the current in each of the 
outside wires exceeds 100 amperes, while the potential hetween each of the 
outside wires and the middle wire does not exceed 500 volts. Series trans- 
formers are used to reduce the current to the meter. This arrangement is 
correct for either a three-wire two-phase or a three-wire three-phase system. 




Fig. 26. Connections for Polyphase Circuit ; Potential exceeding 500 Volts. 



The illustration shows the method of connecting two meters to a poly- 
phase three-wire system carrying currents at a potential exceeding 500 volts. 
It Avill be noted that both series transformers and shunt transformers are 
used. This connection is correct for either a three-wire two-phase or a 
three-wire three-phase system. 



WESTINGHOUSE INTEGRATING WATTMETERS. 625 



WESTIXGHOVIE IIVTEGRATOG WATTMETERS. 

Two-Wire, Single-Phase. — The two-wire single-phase meter is 
rated for the average load of the installation, this being permissible on 
account of its ability to safely carry a load fifty per cent in excess of its 
rated capacity. It registers in International Watts the true energy deliv- 
ered to the circuit, and it is said to be correct for all power factors. The 
counter reads directly in watts or kilowatt hours. Series transformers are 
used on all circuits carrying more than 80 amperes, and for voltages above 
500 volts shunt transformers are also used. These meters are connected to 
two-wire, single-phase circuits, as shown in Figs. 21, 22 and 23. 

Three-Wire, Single-Phase. — This meter is made to register the 
energy delivered by a three- wire circuit, through the medium of a specially 
designed series transformer, having two primary coils and one secondary 
coil. 

One of these primary coils is connected in series with one of the outside 
wires of the three-wire circuit, and the other primary coil is connected in 
series with the other outside wire of the three-wire circuit. The secondary 
coil, in which the current is proportional to the sum of the currents in the 
two primary coils, is connected to the wattmeter. The shunt circuit of the 
wattmeter is connected between the neutral and one of the outside wires. 

The current capacity, marked on the counter of the three-wire Westing- 
house wattmeter, represents the current in each of the outside wires of the 
three-wire circuit. The voltage marked on the counter is that between one 
of the outside wires and the neutral wire. 




Fig. 27. Diagram of Connections of Westinghouse Three-Wire, Single- 
Phase Integrating Wattmeter. 

The total current capacity of a three-wire wattmeter is, therefore, twice 
that marked on the counter, which represents the capacity of one side only. 

The counter records, however, the total energy supplied to both sides of 
the three-wire installation ; and the watt hours recorded on the counter in 
one hour, when the meter is running at full load, will be twice the product 
of the current and the voltage marked on the face of the counter, 



626 



ELECTRICITY METERS. 



Two- or Three-Phase Meters. 

The "Westinghouse polyphase meter records on a single dial the total 
energy delivered in all the phases of a two or three-phase circuit under all 
conditions of balance and of power factor. 

The current capacity marked on the counter of the polyphase wattmeter 
is the current in each wire of the circuit ; the voltage is that across a phase. 
No constant or factor is used. 

Instructions for Checking- and Testing- Westingliouse 
Integrating Wattmeters. 

Registration. — These meters as shipped are ready for use, and are 
accurate within the limits specified on the tag attached to them. 

The disk revolves 50 times per minute at full load; the direction of rota- 
tion being from left to right. The unit of power is the international watt, 
and all wattmeters register directly in watts or kilowatt hours without the 
use of constants. 

Methods of Checking. — One of the two methods mentioned below 
are recommended, circumstances dictating which of the two is the better. 
First method is to compare the instrument to be checked with a standard 
indicating wattmeter, and timing the disk. 

Second method is by comparing with a standard integrating wattmeter. 

First Method - Two-Wire, Single-Phase Wattmeter. — 

Connect the instrument to be compared in circuit with a standard indicat- 
ing wattmeter, as shown in the following diagram. 




WESTINGHOUSE 
INTEGRATING 
WATTMETER 



STANDARD INDICATING WATTMETER 

Fig. 28. 



Load the circuit until the desired reading is obtained on the indicating 
wattmeter, and keep it at a constant value while the integrating wattmeter 
is being read. Time the revolutions of the disk with a stop-watch, com- 
mencing to count when the spot on the disk has made one revolution (after 
the Avatch has started), and counting the revolutions for at least a minute. 

To arrive at the number of watts registered by the wattmeter, use the 
following formula : 

Watts = -TnK. In this formula, R= complete number of revolutions of 

the disk in time T. 

T= time in seconds of revolutions R. 

K = constant. 

For wattmeters that are used without transformers, K =z volts multiplied 
by amperes (as marked on the counter), multiplied by 1.2. For wattmeters 
that are used with series transformers (but checked without them), JT=: 
volts, as marked on the counter, multiplied by 6. For wattmeters that are 
used with both shunt and series transformers' (but checked without them), 
K =600. 

In this way a wattmeter can be compared with a standard, and by varying 
the number of watts can be checked through its entire range. 



WESTINGHOTTSE INTEGRATING WATTMETERS. 



627 



All wattmeters for circuits exceeding 80 amperes are wound for 5 am- 
peres, and are made to register the energy delivered by the main circuit by 
means of series transformers. The primary coils of these transformers, 
which are of heavy capacity, are connected in the main circuits, while the 
secondary coil, in which the current is proportional to the current in the 
primary windings, is connected to the wattmeter. These wattmeters can 
be tested without the series transformers, but should be connected as in 
Fig. 31 following, and the test made in the manner indicated. The full load 
is, however, the product of the voltage marked on the counter multiplied 
by 5, and not by the current indicated on the counter. K, in this case,= 
volts, as marked in the counter, x 6. 

All wattmeters of voltages exceeding 400 volts are provided with 100-volt 
shunt-coils and 5 ampere series-coils, and are connected to the main circuit 
through shunt and series transformers of the proper ratio. In checking, 
connect without the series or shunt transformers to 100-volt circuit, as 
shown in Fig. 28, and proceed as indicated above, remembering that full 
load is 500 watts, and that in the formula Kz=z 600. 

Three-Wire, Single-Phase. —These wattmeters are all 5-ampere, 
single-phase instruments, and the method of connecting them for the first 
method of test is shown in Fig. 29. 




WESTINGHOUSE 
INTEGRATING 
WATTMETER 



m 



STANDARD INDICATING WATTMETERS 

Fig. 29. 

A. Connect two standard indicating wattmeters, one into each side of 
the three-wire circuit, being careful to have the connections of these stand- 
ard wattmeters made on the supply side of the integrating wattmeter, as 
shown, so that it will not measure the energy used by them. Load the cir- 
cuit until the desired readings are obtained on the indicating wattmeters, 
and keep at a constant value while the integrating wattmeter is being read. 
Time the number of revolutions of the disk as before. To arrive at the 
number of watts registered by the wattmeter, use the following formula : 

Watts = ~K. 

R =z number of complete revolutions in time T. 

T = time in seconds required for revolutions li. 

K= constant (volts times amperes, as marked on the counter, multiplied 
by 2.4). 

The reading of the integrating wattmeter should equal the sum of the 
readings of the two standard indicating wattmeters. 

B. A simpler method is to check the wattmeter without the series trans- 
former. As previously mentioned, all these wattmeters are 5-ampere, 100- 
volt, single-phase, two-wire instruments. For purposes of test it is neces- 
sary only to connect them, as shown in Fig. 31, into a single-phase, two-wire 
circuit, with a standard indicating wattmeter, and proceed in the same 
manner as for two-wire wattmeters of this capacity. 

1*©1 yphase Wattmeter. — To compare a polyphase wattmeter with 
the standard, check each side separately on a single-phase circuit. Where 
transformers are not used in connection with the wattmeters, the full-load 
rating for each circuit of the wattmeter is the number of watts obtained by 
multiplying the current by the voltage marked upon the dial of the watt- 
meter. 



G28 



ELECTRICITY METERS. 



If a series transformer is used with the wattmeter, full load in each cir- 
cuit is the number of watts obtained by multiplying the voltage marked 
upon the dial by 5, as all wattmeters used with series transformers are 
wound for 5 amperes. 

In testing, connect the polyphase wattmeter as shown in Fig. 30. Both 
shunt circuits of the integrating wattmeter are connected. The main cur- 
rent, however, is passed through only one series coil at a time, by connect- 
ing "C " to "A" or to "B." When one circuit of the wattmeter is fully 
loaded the rotating element makes 25 revolutions per minute, and 50 revolu- 
tions when both phases are fully loaded. 




Fig. 30. 

Load the circuit until the desired reading is obtained on the indicating 
wattmeter, and keep it at a constant value Avhile the integrating wattmeter 
is being read. Time the revolutions of the aluminium disk for at least one 
minute. 

To arrive at the number of watts registered by the wattmeter, use the fol- 
lowing formula : 



Watts =^,K. 



Where 



R ■=. complete number of revolutions of the disk in time T. 
T= time in seconds of revolutions R. 

K =z constant. (For wattmeters which are used with both series and 
shunt transformers, but checked without them, K— 1200.) 
Always be sure to have both shunts connected when testing. 

Second IVEethod: Witli Standard Integrating* Wattmeter. 
Jiing-le-Pliase Wattmeters. — When using integrating wattmeters 




STANDARD 

WESTINGHOUSE 

INTEGRATING 

WATTMETER 



WESTINGHOUSE 
INTEGRATING 
WATTMETER 



Fig. 31. 



as standards, use one of same capacity and voltage as those under test. 
Load the circuit into Avhich the wattmeter is connected. If the disk of the 
instrument under test runs in synchronism with the standard wattmeter it 
is in correct calibration. Repeat for several different loads. Another 
method is to allow the instrument under test to run with the standard for 
several hours under full load. A comparison of the amount registered 



WESTINGHOUSE INTEGRATING WATTMETERS. 



629 



will show the difference between the two, or the error of the instrument 
tested. 

When but a single wattmeter is to be checked against the standard, it 
shonld be connected as shown in Fig. 31. 

When more than one wattmeter is to be checked against the standard, 
they should be connected as indicated in Fig. 32. 

Referring to Fig. 32 : If a short run is to be made, but one meter should 
be run with the standard at a time, otherwise the meter near the line con- 
nection will measure the energy taken by the shunts of those near the 
standard. If, however, the test is to be made by allowing the wattmeters to 




STANDARD WESTINGHOUSE 

WESTINGHOUSE INTEGRATING- 

INTEGRATING WATTMETERS 
WATTMETER 



Fig. 32. 



run with the standard for several hours they can all be run together, as the 
amount of energy used by the wattmeters themselves will be so small a per- 
centage of the total readings that it will not be noticeable. 

Polyphase W a ttm eters. — Polyphase wattmeters should be checked 
against single-phase standards. The standard used, however, should be of 
twice the current capacity marked on the counters of the polyphase watt- 
meters. Connect as shown in Fig. 33. 

The wire at "A" is connected first to the upper phase of the meter and 
then to the lower phase, proceeding in the same manner as with single- 
phase meters, noting, however, that the full-load speed of the disk will be 
25 r.p.m., as only one phase will be on at a time. 

Be sure to always have both shunts connected when making a test. In 
meters which do not use series transformers there is only one shunt termi- 
nal (the other wire of the shunt being connected to the right-hand series 
terminal inside the meter). 



LOAD 




STANDARD 
WESTINGHOUSE 
INTEGRATING 
WATTMETER 

WESTINGHOUSE 
INTEGRATING 
WATTMETER 




FIG. 33» 



Fig. 34. 



Fig. 34 shows the method of connecting three-wire, single-phase Westing- 
house wattmeters to three-wire circuits. 

All three-wire, single-phase Westinghouse wattmeters, for circuits ex- 
ceeding 400 amperes per side, are connected in this manner. 

Fig. 35 shows the method of connecting polyphase Westinghouse watt- 
meters to two-phase circuits. 



630 



ELECTRICITY METERS. 



All polyphase Westinghouse wattmeters for two-phase circuits of 400 
volts or less, and of 80 amperes or less, are connected in this manner. 




Fig. 35. 



The following illustration shows the method of connecting polyphase 
Westinghouse wattmeters to three-phase circuits. 

All polyphase Westinghouse wattmeters for three-wire, three-phase 
circuits of 400 volts or less, and of 80 amperes or less, are connected in this 
manner. 




Fig. 36. 

The following illustration, Fig. 37, shows the method of connecting poly- 
phase Westinghouse wattmeters to two-phase circuits. 

All polyphase Westinghouse wattmeters for two-phase circuits of 400 volts 
or less, and greater than 80 amperes capacity, are connected with series 
transformers in this manner. 

Fig. 38 shows the method of connecting polyphase Westinghouse watt- 
meters to three-phase circuits. 

All polyphase Westinghouse wattmeters for three-phase circuits of 400 
volts or less, and of greater than 80 amperes capacity, are connected with 
series transformers in this manner. 



WESTINGHOUSE INTEGRATING WATTMETERS. 631 



Fig. 39 shows the method of connecting polyphase Westinghouse watt- 
meters to two-phase circuits. 

All polyphase Westinghouse wattmeters for two-phase circuits of all 
current capacities, and for more than 400 volts, are connected with shunt 
and series transformers in this manner. 





Fig. 37. 



Fig. 38. 



Fig. 40 shows the method of connecting polyphase Westinghouse watt- 
meters to three-phase circuits. 





Fig. 39. 



Fig. 40. 



All polyphase Westinghouse wattmeters for three phase circuits of all 
current capacities, and for more than 400 volts, are connected with shunt 
and series transformers in this manner. 



632 



ELECTRICITY METERS. 



To Tell the Exact Current Flowing- at Any Time in a 
Schallenberg'er Jfleter. 

Note the number of revolutions made by the small " tell-tale" index on 
the top of the movement, in a number of seconds equal to the constant of 
the meter. The number of revolutions noted will correspond to the number 
of amperes passing through the meter. For example : the 20 ampere meter 
constant is 63.3 ; if the index makes ten revolutions in 63.3 seconds, 10 
amperes are passing through the meter. In order to avoid errors in reading, 
it is customary to take the number of revolutions during a longer time, say 
120 seconds ; then as a formula, we have : 



Number of revolutions X meter constant 
Number of seconds 



=: Current. 



KTHIce*" 



r WEsrwHduK Eucmtc £ 







©e© 



OO930 *Jimperc hours. 


07&30 %/lmpere -hours. 




'WBS' 

©00 

ioooos IO00* IOO» 



s??3o vlm/Hinc-Jioura oosoo Jlmpera-ficura. 




J Pfjfl Cj 




arr.io\/Jmpere-houra 

Fig. 41. Dials showing Sample 

Readings. Fig. 42. Difficult Meter Readings. 



THE SCHEEFER WATT-METER. 



633 



THE 8GHBEIIIH WATI-METEB. 

This meter, made by the Diamond Meter Co., Peoria, 111., is another of 
the induction type, used for alternating currents, and has some special 
features. The two following cuts illustrate its latest development. 




Fig. 43. Round Pattern, Type D. 
Scheeffer Watt-Meter Closed. 



Fig. 44. Round Pattern, Type D. 
Scheeffer Watt-meter Open. 



A very ingenious device is used for sensitive adjustment, and the follow- 
ing cut and description 'taken from the Company's catalogue is sufficiently 
clear to indicate its use. 




Fig, 



Meter Core. Showing Shields for Sensitive Adjustment. 



There are two knurled posts, A and B, secured to the meter core by screw 
clamps as shown in the cut. These posts carry iron shields that can be 
made to embrace more or less of the disk by turning the posts. 

" When the iron piece or shield embraces the disk it exerts an influence 
inductively on the disks so as to give it a torque, and will cause it to revolve 
slightly. The left-hand piece (looking at the meter in front) will cause a 
torque towards the right, and the right hand piece toward the left.' If the 
two pieces equally embrace the disk they will balance each other, and no 
movement will result. By throwing one out the other will prevail, and cause 



634 



ELECTRICITY METERS. 



it to revolve. Thus the two pieces can be adj usted towards each other so that 
the meter is always balanced and just on the point of turning, and is highly 
sensitive to extremely small loads. Great care must be taken so the balance 
is perfect, as otherwise the meter will be overcompensated, and will slowly 
run on pressure, and record when no load is on. When this adjustment is 
made, a good way to establish a balance is to keep tapping the meter when 
adjustment is made, as this will give a better adjustment for the meter, as a 
meter will often not run on pressure wben quiet, but run slowly when sub- 
jected to vibrations. A very good way to calibrate a meter is to adjust the 
full load, and then adjust the knurled brass posts, so that by tapping a bal- 
ance of the meter is effected so as not to run on pressure. This condition 
will leave the meter highly sensitive and correct, as it is not necessary that 
the lower loads be calibrated by a Watt-meter. When the posts have been 
properly adjusted, they must then be fastened securely by screwing the 
clamp which holds them tight, so that they will not be distured." 

In testing or calibrating " Scheeffer " meters, use a stop-watch for timing 
and the following formulae for determinations. 



I?1ETEI8 CALCULATIOHi. 



R — revolutions. 
W = watts. 

C =r constant on meter dial. 
S = second. 
Wx s 



w 



R = 



x C 



R X 3,600 X C 


S 


R X 3,600 X 



w 



WEIEH PMCB CHART. 

The General Electric Company furnishes a large price-chart for facilitat- 
ing the making of bills from meter readings. The above cut is a reduced 
facsimile of the chart. The figures at the bottom are kilowatt-hours ; those 
at the left are the amounts of bills in dollars and cents. The diagonals are 
different rates per kilowatt-hour. Selecting the diagonal having the rate at 
which charges are to be made, a point is found on it directly over the num- 
ber of kilowatt hours shown by the meter ; in the column at the left, on a 
horizontal line from the same point, will be found the amount of bill. For 
exar. pie, take 50 kilowatt hours at 10 cents per kilowatt hour, the amount of 
bill shown at the left is $5.00. 



$13.00 

12.00 

11.00 

10.00 

9.00 

8.00 

.f.OO 

6.00 

6.00 

4.00 

8.00 

2.00 

1.00 
.60 



1 


1 1 1 1 1 1 1 1 1 1 1 1 


1 


-&- 




>' .* 










-? 


1 


1 1 1 1 1 1 II II 1 1 


1 


*$ 




r>/ 




/ 












PRICE CHART 
? DETERMINING THE AMOU 
F BILLS AT VARIOUS RATES 
PER 1.000 WATT-HOURS 




M- 




,c ¥ , 


/_ ' 


















> M 


> y 




' 














?V 1 »«T { 


&* ~< 


y 












4< 




>fWm 


U y 
























v 


s^ 




/<><?/[ 


W 






/ 






















7 


yz<& 


T J 






















"f 






-A 


Im 






















/" 




w 


V 


<oS^4 


W 


K 


















/ 


/ 


/ k* 


!*' 








\H 


o. 




f 


** 








/ 




/ / 


/ y 




,' 


KV-r 


' 












u 7 




/ 






*T\ 


,-C 


-> , 


- - ? eg ; 


















[/ 




V' 


' ' 


<vr 


V* 


2-^ ' 
















fi 








,' 


i^U c 




















* /z 


y 


y 


' s 






















r 


~*/4- 


y 




y 
























Z2 


zw 






*' 


<■* 






















?^l 


YrK 


^ 




























/zz£ 


<s> 






























/^^K? 


v^y 






























ill^" 


" i 


RDINATES 


= AM0 


UNT OF BILLS IN DOLLARS AND CENTS 


A 


%$> 


t 


BSCISSAE=THOUSANDSOF WATT-HOURS 


A 




1 II 1 1 1 II 1 1 II II 1 1 1 1 1 1 1 1 1 1 II 



12 16 20 24 .28 32 30 40 44 



32 5G 00 04 08 72 



Fig. 49, Meter Price Chart. 



WEIGHT DISCOUNT METER. 



635 



WRIGHT DliCOIJlI MEIER. 

This instrument is for use in connection with a watt hour meter for de- 
terming the maximum use of current during any given period ; or may be 
used without the watt-hour meter in connection with any electrical device 
for which it is desired to know the maximum use of current, either direct or 
alternating. 

It is slow acting so as to take no account of momentary spurts such as 
starting an elevator or street car, and is rated to record as follows : ' 

If the maximum load lasts 5 minutes, 80 % will register ■ 
If the maximum load lasts 10 minutes, 95 % will register ■ 
If the maximum load lasts 30 minutes, 100 % will register.' 

The following figure shows the working parts in theory, which, being of 
glass and liquid, are placed in a cast-iron case, with a glass front to permit 
reading. As shown, one leg of the circuit passes around a glass bulb which 
is hermetically sealed, and connected to a glass tube holding a suitable 
liquid. 



T HW 



T, Terminals. 
H w, House wires. 
B w, Resistance wire. 
H B, Heated bulb. 




A B, Air Bulb. 

i t, Indicating tube. 

L, Liquid. 

^> Direction. 



Fig. 47. Wright Discount Meter. 



The heat due to the current passing in the circuit expands the air in the 
bulb, which forces the liquid down in the left column and up in the right. 
Should the quantity of heat be such as to force some of the liquid high enough, 
it will fall over into the central tube, where it must stay until the instru- 
ment is readjusted. The scale back of the central tube is calibrated in am- 
peres on the left and in watts on the right. After reading and recording 
the indication for any period of time, the liquid is returned to the outer 
tubes by simply tipping up the tubes, etc., which are hinged at the top 
connections for the purpose. 

The readings of the demand meter or discount meter, either of which names 
are used, together with those of the watt-hour recording meter, furnish a 
basis for a more rational system of charging for electricity than has been 
customary. This subject is being taken up by many of the larger electricity 
supply companies. 

The instrument is handy to use in circuit with a transformer to show how 
the maximum demand compares with the transformer capacity ; also on 
feeders and mains to show how heavily they may be loaded. 



TELEGRAPHY. 



In this chapter only the instruments used in telegraphy will he noticed ; 
and these, with their connections, in theoretical diagrams only. For the 
various details, whose presentation would defeat the purpose of clearness 
in this compilation, readers are referred to various works on telegraphy. 
Lines, batteries, etc., are each treated in other chapters. 



AMERICAN, or CIOSED CIRCUIT METHOD. 

The following diagram shows the connections of the Morse system of 
single telegraphy, as used in the United States. The terminal stations only 
are shown, and in one case the local circuit is omitted. Several interme- 




LINE TO TERMINAL 



LOCAL BATTERY 
EY 



— YAWW— U 



± 



MAIN 

BATTERY-=- 



Fig. 1. 

diate stations (in practice 25 is not unusual) may be cut in on one circuit ; 
all the instruments working in unison, in response to one key only. 

In Fig. 1 at either end is a key which, when open, allows the now un- 
attracted armatures to be withdrawn by the retractile spring, S. Closing 
the key restores the current to the relays, attracts the armatures to the 
front stop ; the local circuit through the relay points is closed, and the 
signal is heard on the sounder. The attracting force of spring, S, is less than 
that of the relay cores as energized by the current from the battery used 
for a given circuit. It can, by "pulling up " on the spring, be made greater ; 
in which case the given current is ineffective to close the relays, and if the 
tension of spring, S, is maintained, battery must be added to close the relays. 
It is possible, therefore, by means of spring, S, to make a comparatively 
weak current ineffective to close the relay points. The significance of this 
will appear later in connection with the quadruplex. 



EVROPEAIT, or OPMST CIRCUIT METHOD. 



The following diagram shows the connections of one terminal station with 
the line connecting to the next. The ground plates may be dispensed with 
if a return wire from the next station is used, thus forming a metallic cir- 
cuit. 

This method of connecting Morse apparatus is used mostly in Europe, and 
has two advantages over the American method . 

a. The battery is not in circuit except when signals are being sent. 

b. When the key is closed and the current admitted to line, the coils of 
the relay are cut out of the circuit, thus lessening the hindrance to the flow 
of current. 

636 



TELEGRAPHY. 



637 




LINE TO NEXT STATION KEY 



REPEATERS. 

In practical telegraphy, the high resistance of the line wire between the 
terminal stations, and imperfect insulation permitting leakage in damp 
weather, make it inexpedient to attempt to transmit signals over circuits 
whose lengths have not well-defined limits. But a circuit may be extended, 
and messages exchanged over longer distances by making the receiving 
instrument at the distant terminal of one circuit do the work of a transmit- 
ting key in the next. The apparatus used for this purpose is called a re- 
peater, and is usually automatic, in a sense which will appear later on. 

From among the scores of repeaters, selection must be made of repre- 
sentative types, — the two in most general use. 



JVEilliken Repeater. 

The following diagram illustrates the theory of the Milliken repeater, 
which is in general use in the United States and Canada. The essential 
feature of every form of automatic repeater is some device by which the 
circuit into which the sender is repeating not only opens when he opens, but 
closes when he closes. 




638 



TELEGRAPHY. 



In the diagram is represented the apparatus of a repeating station in 
which appear the instruments and three distinct circuits in duplicate, viz. : 
the east and west main line ; east and west local (dotted) ; east and west 
extra local (dash and dot). Starting with both "east" and " west" keys 
closed and the line at rest, battery b', whose circuit (dash and dot) is com- 
plete through transmitter, T / , energizes extra magnet, E', attracts the pen- 
dent armature, P', leaving the upright armature free, the pendent armature,. 
P, being similarly held by battery, b. In operation, the distant east opens 
his key, relay, E, opens, then transmitter, T, through whose tongue and post 
passes the west line, which opens, and would open relay, W, and therefore; 
transmitter, T' ; but at the moment transmitter, T, opens, the extra local 
circuit (dash and dot) opens, releasing pendent armature, P, which is drawn 
by its spring against the upright armature holding closed the points of relay, 
W, and transmitter, T 7 , and therefore the east line, which passes through 
its tongue and post. When the distant west breaks and sends, the action 
begins with the west relay instead of east, and follows the same course. 



Weiny-Phillips Repeater. 

A theoretical diagram of the Weiny-Phillips repeater is given herewith. 
It is in general use by one of the principal telegraph companies, and is 




Fig. 4. 



J Li Tiii 



introduced here because it involves the principle of differentiation in mag- 
net coils, which plays so important a part in duplex telegraphy. As in the 
Milliken, there are three distinct circuits in duplicate ; and in the diagrams 
the parts performing like functions in the two types of repeaters are simi- 
larly lettered. The connections and functions of the main line (solid black) 
circuits and of local (dotted) circuits, are identical with those of the Milli- 
ken. But instead of the extra magnets and pendent armature of the latter, 
we have a tubular iron shell inclosing a straight iron core and its windings, 
the combination of shell and straight core performing the same functions 
as the usual horse-shoe core. The turns of wire around the core of the 
extra magnet are equally divided, and the current traverses the two halves 
in opposite directions. Such a core is said to be differentially wound, be- 
cause the core is energized by the difference in strength of the currents in 
the coils ; but when the coils are equal in resistance, the equal currents, 
passing in opposite directions around the core, neutralize each other. If 
one of the coils is opened, the core at once becomes a magnet capable of 
holding the armature at the moment when, the repeater in operation, the 
" east " station opens his key, opening relay, E ; then transmitter, T ; then 
opening the " west" wire, which would open relay, W, transmitter, T', and 
therefore the east wire ; but the opening of transmitter, T', is prevented by 
the energizing at the critical moment of core W one coil of which is opened 



DUPLEX TELEGRAPHY. 



639 



when transmitter, T, opens. When the distant west hreaks and sends, the 
action begins with the west relay instead of the east, and follows the same 
course. 

DIPIEX TEJLEGHJLJPHY. 

That method of telegraphy by which messages can be sent and received 
over one wire at the same time is called duplex ; and the system in general 
use, known as the polar duplex, is illustrated in the accompanying diagram. 
In single telegraphy all the relays in the circuit, including the home one, 
respond to the movements of the key ; the duplex system implies a home 
relay and sounder unresponsive, but a distant relay responsive to the move- 
ments of the home key ; and this result is effected by a differential arrange- 
ment of magnet coils, of which the extra magnet coils in the Weiny-Phillips 
repeater furnished an example. A current dividing between two coils and 
their connecting wires of equal resistance will divide equally, and passing 
round the cores, will produce no magnetic effect in them. This condition 



WEST 




IH 



^^ 



Mil 



EAST 




THEORETICAL DIAGRAM OF POLAR DUPLEX 
balancing switch omitted 
Fig. 5. 



is established when the resistance of the wire marked — > <— in the diagram 
is balanced by the resistance of a set of adjustable coils in a rheostat marked 
R. This is called the ohmic balance (from ohm, the unit of resistance) ; and 
tbe static balance is effected by neutralizing the static discharge on long 
lines by means of an adjustable condenser, C, and retardation coil, r, shunt- 
ing the rheostat as shown. In the single line relay the movement of the 
armature is effected by the help of a retractile spring in combination with 
alternating conditions of current and no current on the line. In the polar 
relay the spring is dispensed with, and the backward movement of the arm- 
ature is effected, not by a spring, but by means of a current in a direction 
opposite to that which determined the forward movement. This reversal 
of the direction of the current is effected by means of a pole-changer, PC, 
whose lever, T, connected with the main and artificial lines, makes contact, 
by means of a local circuit and key, K, with the zinc ( — ) and copper (-(-) 
terminal of a battery alternately. Tbe usage in practice is zinc to the line 
when the key is closed ; copper, when open. The law for the production of 
magnetic poles by a current is this: When a core is looked at "end on" 
a current passing round it in the direction of the hands of a clock produces 
south-seeking magnetism, S ; in the opposite direction, north-seeking mag- 
netism, marked N. A springless armature, permanently magnetized and 



640 TELEGRAPHY. 

pivoted, as shown in the drawing, will, if its free end is placed between S and 
N magnetic poles, be moved in obedience to tbe well-known law that like 
poles repel, while unlike poles attract each other. The " east " and " west " 
terminal is each a duplicate of the other in every respect ; and a description 
of the operation at one terminal will answer for both. 

Under the conditions shown, the keys are open ; and the batteries, which 
have the same E.M.F., oppose their copper (+) poles to each other, so that 
no current hows in the main line. But in the artificial line the current 
flows round the core in such direction as, according to the rule just given, 
to produce N and S polarities as marked, opening the sounder circuits at 
both terminals. If, by means of key, K', the pole-changer, PC / , of " east" 
station is closed, the connections of battery, W, are changed ; it is said to 
be reversed; and it now adds its E.M.F. to that of battery B, the current 
flowing in a direction from " west" to " east" ; i.e., from copper to zinc. 
But the current in the main line is to that in the artificial as 2 to 1 ; and if 
the relative strength of the resultant magnetic poles is represented by small 
type for that produced by the current in the artificial line, and by large type 
for the main, the magnetic conditions can be graphically shown, as they are 
produced on each side of the permanently magnetized armatures marked 
(N) and (N 7 ). In relay, PB/, it is Sn (N 7 ) sN, causing it to remain open ; in 
relay PR it has changed to Ns (N) nS — just the reverse of that shown in 
the diagram — the relay therefore closes, and the sounder also. If key, K, 
of the west station is closed at the same time, the batteries are again placed 
in opposition, but with zinc (— ) poles to the line, instead of, as in the first 
instance, copper (-|-) poles. The result is no current on the main line ; but 
the current in the artificial lines, flowing in the direction from the ground 
(whose potential is 0) to the zinc ( — ) of the batteries, the magnetic condi- 
tion at " east" station is represented by n (N 7 ) s, which closes relay, PR 7 ; 
and at " west " station by n (N) s, which closes relay PR. The conditions 
necessary to duplex work, viz., that the movement of key, K 7 , should have 
ho effect on relay, PR 7 , but should operate the distant relay, PR, are thus 
fulfilled, and the transmission of messages in opposite directions at the same 
time is made practicable. In the case of the Wheatstone Automatic duplex 
this exchange goes on at high rate of speed, the maximum rate being 250 
words a minute. 

Duplex Repeater. 

In wires worked in the duplex or quadruplex system, the static capacity 
of the wire, which plays little if any part in the operation of circuits by the 
single method, places a limit on the length of the continuous circuit. But 
the distance between working stations can be greatly extended by the use 
of repeaters in which, by an arrangement perfectly simple, the pole-changer 
of a second circuit is controlled by the relay points of the first. The long- 
est regular circuit in the United States is that worked between New York 
and San Francisco, with six repeaters. 

The quadruplex system of telegraphy allows of two messages being sent 
in either direction, over the same wire, and at the same time. In theory it 
is an arrangement of two duplexes, so different in principle as to permit 
of their combination for the purpose designated. If the accompanying dia- 
gram of the quadruplex is examined, there will be noticed in it the pole- 
changer, polar relay, and all the apparatus of the polar duplex. The polar 
relay at the " east" station (not shown) will respond to signals sent by the 
pole-changer, PC, at the " west " in the manner described in the paragraph on 
the Polar Duplex, so long as the working minimum of current is main- 
tained. This working minimum can be doubled, trebled, or quadrupled 
without appreciable difference to the polar relays. In the paragraph on 
Single Telegraphy, the operation of the single relay, fitted with a retractile 
spring, was effected by opening and closing the key ; or, in other words, by 
alternating periods of "no current" and "current "on the wire. It was 
further stated, in anticipation of its introduction at this point, that the 
spring could be so adjusted that a weak current, though flowing all the 
time through the coils, would not close it. To effect the closing an increase 



THE STEARNS DUPLEX. 



641 



of battery, and therefore of current strength is necessary, so that the relay, 
instead of, as in the first instance, responding to alternating periods of " no 
current " and " current " could be operated by alternating periods of " weak 
current" and "strong." In the diagram, transmitter T, when its key is 
open, admits to the line a current sufficient to operate the polar side ; and 




THE QUADRUPLEX (one terminal) 
Fig. 6. 

at the " east " station (not shown) there is a differentially wound relay, M', 
the duplicate of relay M in the diagram, the tension of whose spring makes 
it unresponsive. But when all the battery is on, a condition which obtains 
when the key closes transmitter, T, the distant relay, M', is closed. In short, 
there is in the quadruplex a pair of polar relays which respond to changes 
in the direction, not in the strength of the current ; and a pair of neutral 
relays, which respond to changes in the strength, not to the direction of the 
current. The diagram shows the apparatus in its simplest form ; there are 
a number of details in connection with its operation, the complete connec- 
tions for which are rather too complicated for this book. On page 199 of 
Mavers's American Telegraphy will be found a diagram embodying the full 
scheme of connections ; and Thorn and Jones' Telegraphic Connections con- 
tains diagrams and detailed descriptions of the systems in general use. 

THE KTKARXM DUPLEX. 

The operation of differential relays like M in the diagram of the quadru- 
plex, by alternations of "no battery "and "battery," is tbe principle of 
the Stearns duplex which, as the first condenser-using, and therefore static- 
eliminating duplex in the world, has a certain historic interest. In Febru- 
ary, 1868, there were in use by the Franklin Telegraph Company a duplex, 
set New York to Philadelphia, and another to Boston ; and in August, 1871, 



LjvWW— — 




STEARNS DUPLEX 

(ONE TERMINAL) 



642 TELEGRAPHY. 

by the Western Union Telegraph Company, a duplex, New York to Albany 
— all without condensers. In March, 1872, the Stearns Duplex, with con- 
denser, went into operation between New York and Chicago, but it has been 
superseded by the polar system. 

Reverting to the diagram, the pole-changer with its adjuncts, and the 
polar relay of the quadruples, are omitted ; one pole of the battery is 
grounded, and the lever of transmitter, T, is grounded through a resistance 
equal to that of battery, B. This grounds the line through tongue, T, and 
leaves the battery open at the post, P. The " east " station (not shown) is a 
duplicate of the " west," and the control of relay, D, by the distant trans- 
mitter, T', may be traced as follows. Suppose distant transmitter, T', sends 
copper to the line when closed, the current dividing equally between the 
main and artificial lines in distant relay, D', has no effect upon it ; but at the 
west station there is no current in the artificial line in relay, D, so that 
the current in the main line closes it. Open the key, K.', and the line is 
grounded through the lever of transmitter, T v ; battery P/is open, and there 
being no current on the wire, relay, D, is open in response to the opening of 
distant key, K'. Let transmitter, T, now be closed, and trace the control of 
relay, D, by the distant key, K'. The current, which now flows from the 
ground through the lever of open transmitter, T x , to the zinc pole of battery, 
JB, is neutralized in relay, D, by an equal current flowing from the ground 
through its artificial line in the opposite direction around its cores, so 
that relay, D, remains open. Now close distant transmitter, T', and the 
current in the artificial line (i.e., through the rheostat, R) of relay D is over- 
powered as to its effects by a current on the main line of twice its strength, 
and relay D is closed. It is thus shown to be controlled by the distant key, 
K7, irrespective of the position of home key, K, and the conditions necessary 
to duplex telegraphy are met. 

TELEGRAPH CODES. 

morse, used in the United States and Canada. 
Continental, used in Europe and elsewhere. 
Phillips, used in the United States for "press " Avork. 

Dash — 2 dots. 

Long dash = 4 dots. 

Space between elements of a letter = 1 dot. 

Space between letters of a word = 2 dots. 

Interval in spaced letters = 2 dots. 

Space between words — 3 dots 

JLetters. 

Morse. Continental. 

E — — 

I 

L 

N ~~ 

R 



TELEGRAPH CODES. 643 

Morse. Continental. 



Numeral*. 

Morse. Continental. 



Punctuations, etc. 

Morse, Continental. 



, Period 

: Colon 

: — Colon dash 

; Semi-colon 

, Comma 

? Interrogation 

! Exclamation 

Fraction line 

— Dash 

- Hyphen 

' Apostrophe 
£ Pound Sterling 
/ Shilling mark 
$ Dollar mark 
d pence 

Capitalized letter 
Colon followed ) 

hy quotation : " J 
c cents 

. Decimal point 
U Paragraph 
Italics or underline 
( ) Parentheses 
[ ] Brackets 
" " Quotation ) 

marks. 
Quotation within 

a quotation 



. Period 

: Colon 

: — Colon dash 

; Semi-colon 

, Comma 

? Interrogation 



Phi Uips 



644 TELEGRAPHY. 



! Exclamation 

Fraction line — 

— Dash 

- Hyphen ■ 

' Apostrophe 

£ Pound Sterling 

/ Shilling mark 

$ Dollar mark 

d Pence 

Capitalized letter — 

Colon followed by quo- \ 

tation : " j 

c cents — 

. Decimal point 

IT Paragraph 

Italics or underline 

{ ) Parentheses 

" " Quotation marks 

Quotation within a ) 

quotation " ' '" j 

Abbreviations in Common Use. 

Min. Minute. Bn. Been. 

Msgr. Messenger. Bat. Battery. 

Msk. Mistake. Bbl. Barrel.* 

No. Number. Col. Collect. 

Ntg. Nothing. Ck. Check. 

N.M. No more. Co. Company. 

O.K. All right. D.H. Free. 

Ofs. Office. Ex. Express. 

Opr. Operator. Frt. Freight. 

Sig. Signature. Fr. From. 

Pd. Paid. G.A. Go ahead. 

Ok. Quick. P.O. Post Office. 

G.B.A. Give better address. B.B. Repeat. 



TELEPHONY. 



THEORY OF THE MACHIfET TEIEPHOHTE. 




Fig. 1. 

Field of Bell Telephone. 



Tlie Receiver. — The following cut is meant to illustrate in a simple 
manner about all that is known of the theory of the magnet or Bell telephone. 
It is well known that the lines of force in a bar magnet curve backward and 
around from one end or pole to the other. If a piece of iron, or say a dia- 
phragm, be placed across one end of the bar, but not touching it, many of 
the lines will traverse the diaphragm, as the path so provided is magnetic- 
ally easier than air. Now, if the diaphragm be moved backward and forward, 
or to and from the end of the bar, a change will take place in the position 
and condition of the lines of force surrounding that end of the magnet ; and 
if a coil of fine wire be placed on the end of the bar close up to the dia- 
phragm, then the changes produced in the lines of force will react on the 
coil of wire (as in a dynamo when the armature is moved across the lines 
of force), and an E.M.F. will be produced in the coil. This is the exact 
condition illustrated in the cut below. 

Now, if the ends of the wire of the coil be extended, and connected to.the 
terminals of an exactly similar instrument, any movement of the diaphragm 
of one will be exactly reproduced in the other 
instrument ; and, therefore, if one talks against 
and so vibrates one diaphragm, the other will 
be vibrated, and speech will thus be repeated. 
"While authorities seem to think that this simple 
theory is scarcely enough to account for all the 
results found in a telephone receiver, yet it 
apparently covers the greater part. 

Based on the above theory, good transmission 
of sound needs : 
A powerful magnet and magnetic field. 
A diaphragm that will vibrate freely. 
A wide, shallow coil, in order to take in as many lines of force as 
possible. The permanent magnet is essential to reproduce the pitch. 

Tlie Transmitter. — Although the Bell receiver proved to be an in- 
strument of the most extraordinary sensitiveness, and as a receiver has 
never been superseded, yet as a transmitter its range is extremely limited, 
and much time has been spent by many minds in developing instruments 
to extend the range of telephonic transmission. 

While many inventors have tried to design a 
transmitter in which the circuit is broken at 
each and every vibration of the receiving dia- 
phragm, yet none have succeeded ; and success- 
ful telephones are based in principle on the 
change of resistance in a circuit, whicb produces 
undulatory curents, and that is exactly the point 
patented by Professor Bell. 

Edison, taking up the principle, devised the 
transmitter known by his name, in which, to pro- 
duce the undulatory currents, he utilized the 
change in resistance of carbon under varying 
pressure. 

The cut herewith shows the design of the Edi- 
son Carbon Transmitter, which was quite a suc- 
cess as a loud-speaking instrument, and was 
doubtless the forerunner of the modern trans- 
mitters. The instrument consists of a button 
of lamp-black, compressed between two metal 
plates to which the conductors are connected, 
with a battery in circuit. An ivory button 
presses against the cake of lamp-black, or carbon, 
and is in turn pressed by the diaphragm. 
Hughes next determined, by his experiments 

645 




Fig. 2. Edison Carbon 
Transmitter. C, Carbon 
Disk ; B, Button ; D, 
Diaphragm. 



646 



TELEPHONY. 



with the microphone, that the maximum effect is produced when the contact 
with or between the particles of the carbon is a loose one. He showed many 
beautiful experiments with that crudely made instrument which is shown 
in principle and as used in the following cuts. 




r 



W 



H 



^=ti 



Fig. 3. Hughes Car- Fig. 4. Diagram of simple telephone circuit for trans- 
bon Microphone. mitting in one direction. C, pressure button ; Z>, dia- 
phragm ; T, loose carbon contacts ; B, battery ; P, pri- 
mary of induction coil ; S, secondary ; E, bell receiver. 

The well known principle of the induction coil was then utilized to mag- 
nify the effects of the undulations ; and thus Avere devised all the essential 
features of the modern telephone transmitter, which are in use to-day in 
every commercial instrument. The following cuts show the simple form in 
which all the above mentioned principles are connected to form a practical 
telephone. 

The principles are : 

The diaphragm, operated by sound vibrations, varying the pressure on 
loose carbon contacts, and varying the resistance in the local circuit so as to 
produce undulatory currents, which are reproduced in the secondary cir- 





FiG. 5. Diagram of simple telephone circuit for conversing, or transmitting 
in both directions. Letters all the same as in previous cut. 



cuit of the induction coil, transmitted over the line circuit to the receiver, 
where the undulatory currents cut the lines of force surrounding the coil, 
and produce exactly similar vibrations in the diaphragm adjacent to it, 
thus vibrating the surrounding air, and producing sound waves identical 
with those directed at the diaphragm of the transmitter. 

Rec«iv«i'8, — The Bell receiver is almost universally used to-day. It 
varies in its construction only in using a single-pole magnet for ordinary 
work, a double-pole magnet for long-distance circuits, and the watch-case 
receiver for desk, speaking-tube and operators' sets. All are shown in the 
accompanying cuts. 

It has been found that a very narrow air-chamber between the diaphragm 
and mouth-piece produces the best results, and that a small hole through 
the rubber of the cap helps also. 

Few if any improvements have been made excepting in the use of better 
quality of materials and better construction. 

The reader is referred to the "Telephone Hand Book" by Herbert Laws 
Webb (Electrician Publishing Co., Chicago), for description of foreign and 
other instruments. 



THEORY OF THE MAGNET TELEPHONE. 



647 



Fig. 6. Magnet 
of Single Pole 
Receiver. 






Fig. 8. Double 
Pole Receiver. 



Fig. 9. Watch 
Receiver. 



Transmitters. — After Edison designed his carbon transmitter, and 
Hughes made the microphone experiments, the Bell receiver was no longer 
used for transmitting purposes, and numerous forms of battery transmitters 
were designed. To-day they are legion, and differ, generally speaking, only 
in inessential details. Only those forms mostly in use will be described here, 
as they illustrate in principle nearly all others. 

None but carbon transmitters are used to-day, and these are in three prin- 
cipal forms or classes ; the first using single contacts, of carbon for varying 
the resistance, as in the Blake ; the second using several contacts ; and the 
third class, known as the Hunning type, using granulated carbon. Granu- 
lar carbon transmitters are more used than any other type. 

Transmitters of the second class are not used to any great extent in the 
United States. The Blake, of the first class, and the " solid back," of the third 
class, are the forms most used by American companies, the latter largely 
predominating since the extensive adoption of metallic circuits. 

I can do no better than quote, in describing these instruments, from 
Webb's " Telephone Hand-Book." 

Blake Transmitter. — For lines of moderate length, the.Bfo.Jte trans- 
mitter will give good service if kept in good adjustment. It is of simple con- 
struction, low first cost, and requires but little battery power. It has the 
disadvantage of needing careful adjustment when set up, and frequent in- 
spection and adjustment while in service. 

Each of the parts has an important function to perform, and on all being 
in good condition depends the efficient working of the instrument. See Figs. 
10 and 11. 

The variable resistance is made in the 
following way : A slender spring, carry- 
ing a platinum contact point, bears on 
the centre of the diaphragm. A second 
spring carries a button of compressed 
carbon let into a rather heavy socket of 
brass. The face of the carbon button 
presses lightly on the platinum contact 
point of the first spring. The vibrations 
of the diaphragm cause the pressure of 
the platinum point on the carbon button 
to vary, resulting in a variation of the 
resistance at the contact. The secret of 
the good working of the instrument is 
that the two sides of the contact have no 
rigid bearing. In Edison's first trans 




Fig. 10. Blake transmitter. I), Dia- 
phragm ; B, rubber band; C, clip ; 
A, damper ; L, iron bracket ; F, 
adjusting-screw. 



mitter he made one carbon contact solid with the case, and the other solid 



648 



TELEPHONY. 



with the diaphragm. Consequently, the variable contact was not sufficiently 
" sympathetic," as it were, with the vibrations of the diaphragm, and the 
instrument did not work well. Blake discovered the reason of the defect, 
and applied the remedy. 

In the Blake transmitter the carbon button " stands up " to the platinum 
contact, securing the full effect of the variations in pressure, because of the 
weight of the brass socket ; that is, because of its inertia, or resistance to be 
set in motion. The platinum contact is held against the diaphragm by the car- 
bon button, but the normal set of its spring is toward 
the button and away from the diaphragm. Conse- 
quently we have a delicately balanced arrangement, 
susceptible to change by the least vibration com- 
municated by the diaphragm to the platinum point. 

The arrangement of the parts to allow of proper 
adjustment of the springs is very ingenious. An iron 
ring is attached to the inside of the case, this ring 
having a bracket, or projection, top and bottom. To 
the top bracket is attached a piece of angle iron bent 
at its upper part to a right angle, at the lower part 
to an obtuse angle. The lower bracket serves as a 
bearing for the screw by which the iron support may 
be adjusted. The top part of the support carries the 
two springs, which are insulated from each other by 
hard-rubber washers. The carbon spring is sheathed 
of with a rubber sleeve, the diaphragm (generally of 
iron) is clamped over a rubber gasket, and is pro- 




Fig. 11 
Blake 



Section 
transmitter. 



Djdiaphragm; S,car- vided with a damper, consisting of a metal spring 
bon spring ; S 7 , plat- screwed to the inside of the case. This damper is 
inum spring ; L, iron rubber-covered, and has a little cloth pad that presses 
bracket; F, adjust- on the diaphragm near its centre. The damper 
ing-screw. checks the vibrations of the diaphragm as quickly as 

they have done their work, preventing continued 
vibrations that would interfere with those following. The adjustment of 
the springs is effected by means of the screw bearing on the obtuse angle of 
the iron support. Turning the screw upward forces the support, and con- 
sequently the carbon button, toward the diaphragm, increasing the pressure 
between the button and the platinum contact. A reverse action of the screw 
allows the support to come away, by reason of the outward set of the spring 
by which it is attached to the iron frame, resulting in a decrease of the 
pressure between the button and the platinum contact. The normal set of 
the spring with the platinum contact gives it a tendency to follow the car- 
bon button, and, if the button is pulled back, the platinum contact should 
follow it nearly half an inch. The best adjustment is when the pressure of 
the carbon button on the platinum contact just holds it lightly against the 
diaphragm, not so lightly as to allow of any separation or break when the 
diaphragm is vibrated by the voice. The two springs of the transmitter 
are, of course, connected in circuit with the primary wire of the induction 
coil and with the battery. The induction coil generally used in the Blake 
transmitter has a resistance in the primary of half an ohm and in the sec- 
ondary of about 250 ohms. 

The " Solid-Back " Transmitter. — The transmitter case is of 
metal, and has much the form of the gong of an electric bell ; it is enclosed 
by a perforated metal lid or cover, to which is attached the mouthpiece. 
The cover carries the entire transmitter, which consists of two small carbon 
disks enclosed in a metal chamber having an insulating lining ; between the 
disks is a layer of finely granulated carbon, and the disks being slightly 
smaller than' the containing chamber, the surrounding space between the 
edges ot the disks and the side of the chamber is also filled with carbon 
granules. The back electrode is in metallic connection with the containing 
chamber, a little pin in the brass backing of the carbon disk fitting into a 
recess in the chamber, and holding it firmly seated. The front electrode is 
insulated from the chamber by the insulating lining of varnished paper and 
by a mica disk or washer, which encloses the chamber when the front elec- 
trode is placed in position. The front electrode is secured to the vibrating 
diaphragm of the transmitter by means of a pin, which extends from its 
brass backing through a hole in the centre of the diaphragm. This pin has 
two threads, one for a nut that clamps the mica washer over the end of the 



THEORY OF THE MAGNET TELEPHONE. 



649 




Section of Solid-Back 
Transmitter. M, mouthpiece ; 
D, diaphragm ; E, front elec- 
trode ; B, back electrode ; W, 
electrode chamber ; P, metal 
bridge piece ; d, set screw ; m, 
mica washer ;p, threaded pin on 
front electrode; e, rubber band; 
/, damper ; C, case ; E, cover. 



chamber containing the two electrodes, and a finer one for two small nuts 
that clamp the electrode to the diaphragm. 

The mica washer is held against the little chamber by a brass collar, 
which screws on the brass chamber itself, and secures the mica washer to it 
around its edge. The mica washer being clamped to the chamber at its peri- 
phery, and to the front electrode at the centre, has sufficient elasticity to 
allow of the electrode-responding to the vibrations of the diaphragm, and at 
the same time the transmitter chamber is effectually closed. The chamber 
has a projecting stud at the back which 
fits into a hole in a stout brass bridge, and 
is there secured by a set screw. The metal 
bridge is screwed to the cover of the trans- 
mitter case. The diaphragm, which is of 
metal, is secured to the cover, and is pro- 
vided with the usual clip and padded 
dampening spring. One end of the brass 
bridge carries a block of insulating mate- 
rial, and to a small binding-post on this 
block a fine wire, attached to the front -& +n 
electrode, is connected. The rear elec- 
trode, being in metallic contact with the 
bridge and through it with the case of the 
transmitter and the supporting arm, needs 
no special connection, one side of the pri- 
mary circuit being connected to the arm of 
the transmitter. The other side is con- 
nected by a cord, which passes through a 
hole in the bell-shaped transmitter-case to 
the binding-post on the insulating block. 

The vibrations of the diaphragm are communicated to the front electrode 
by the pin, which forms a rigid connection between them. The electrode, 
having a certain freedom of movement within the little chamber, varies the 
pressure on the layer of carbon granules between it and the back electrode, 
thereby setting up the usual variation of resistance required in a carbon 
transmitter. The design of the instrument is very good. The two elec- 
trodes, being of carbon, make excellent contact with the carbon granules, 
thus affording the best opportunity for wide variation of resistance under 
vibration, while the carbon electrodes, being soldered to brass disks, good 
metallic contact is obtained with the two sides of the primary circuit. The 

"packing" difficulty is, to a consid- 
erable extent, obviated by this form 
of transmitter. The space in the cham- 
ber around the edges of the electrodes 
contains a certain quantity of granu- 
lated carbon, which is not directly in 
the circuit, and does not become heated 
up rapidly by the current ; and any ex- 
pansion of the granules immediately 
between the electrodes through heating 
causes a displacement of part of the 
heated carbon into the cooler. "When 
the transmitter is out of circuit and 
cools off, the granules tend to resettle 
into their original position. 

The chamber containing the working- 
parts of the instrument is extremely 
small, and forms a sort of button at- 
tached to the front cover of the case. 
By unfastening the screws which hold the cover, the entire transmitter can 
be withdrawn, the connecting cord joined to the insulated binding-post 
having first been disconnected. On account of the smallness and delicacy 
of the parts, great care is required in handling the transmitter when assem- 
bling or taking apart. When properly set up, it needs no adjustment ; and 
indeed there is nothing that can be adjusted unless some radical defect 
exists. Figs. 12 and 13 show the details of construction by means of a sec- 
tion of the transmitter mounted, and a section of the various parts of the 
chamber, and a front view of the chamber 




Fig. 13. Details of 
Transmitter. fF,electrodecham- 
ber ; i, insulating lining; B, back 
electrode ; a, brass backing ; E, 
front electrode ; b, brass back- 
ing; p, thread for nut U; m, mica 
washer ; u, nut for clamping m 
in place ; p f , thread for t and V ; 
c, cover of W; TT, nuts for 
clamping front electrode to dia- 
phragm. 



650 



TELEPHONY. 



HEagrneto Generator and Bell. — The magneto generator has, in 
the United States, displaced every other device for a calling signal for use 
with telephones. 

It is simply a crude form of alternating-current dynamo having permanent 
magnet fields, and but one armature coil with its terminals led out. through 
the shaft, and one contact. To this dynamo circuit is joined a polarized 
hell or ringer. It is made up of a small electro-magnet that is connected in 
circuit with the wires from the small dynamo ; and when that instrument 
is brought into action by revolving its armature, current is sent through 
the coils of the electro-magnet, thus energizing it alternately, first in one 
direction, then in the other, and throwing its armature, or keeper, which is 
pivoted opposite the poles, back and forth, and so vibrating tbe hammer 
attached to the armature between the two gongs mounted above. The polar- 
ized bell has a small permanent magnet fixed to the frame carrying the 
eibctro-magnet, which tends to keep the armature pressed over in one direc- 
tion. Owing to the high resistance of the generator armature, this, when 
not in use, is cut out of circuit, and only the bell coils left connected to the 
line. There are many ways of effecting this change in the circuits automat- 
ically, but the devices employed are so varied that no description will be 
attempted here. The cuts shown embody the theories and general methods 
of connection. 

An extension bell should only be connected in the ringing-circuit, as shown 
in the cut. An extension bell is simply the ringing-portion of a magneto 
separated from the dynamo part, in order that it may be placed in some 
distant location, where it is necessary to get a signal from the telephone. 



^^ 





Fig. 14. 



Magneto-Generator and 
Bell. 



Fig. 15. 



Complete Magneto-Bell. 
Post Pattern. 



Automatic Switches. — In a complete telephone set or instrument 
there are several circuits, or parts of circuits, each having its own applica- 
tion. 

The ringing-circuit consists of the magneto-bell and generator, the arma- 
ture of the latter being individually controlled by an automatic device. 

The talking-circuit, consisting of the secondary of the induction coil, and 
the receiver. 

The primary circuit, consisting of the battery, the variable resistance of 
the transmitter, and the primary of the induction coil. 

The automatic switch must be so designed as to connect the ringing-cir- 
cuit to the line when the instrument is not in use, so that signals may be 
received from other telephones or from the exchange, and to cut out the 
ringing-circuit, and connect the line to the talking-circuit, and close the 
primary circuit when one wishes to talk. 



TELEPHONE CIRCUITS. 



651 



This is almost always done by using the weight of the receiver to hold 
down a switch that will make all the necessary contacts for cutting the 
ringing circuit in when the instrument is not in use. When the weight of 
the receiver is removed, a spring lifts the switch to an upper position, in 
which it closes another set of contacts through the talking and primary cir- 
cuits, and leaves the ringing circuit either open or short-circuited. 

There are so many of these switches that only a diagram of a standard 
plan can be included here. A second diagram shows the proper connection 
for an extension bell. 






JS-i.r 



^^-ur- 



extension npq w 

B ELL _!P lj> 



I Ho) laAAt- 

p/V\NV-[_ 



Fig. 17. Diagram showing proper 
Connections of Extension Bell. 



Fig. 16. Diagram of Connections 
of Series Magneto Bell and 
Telephone Set. 

Requirements of Metallic Circuits. — Metallic circuit telephone 
lines must fulfil the following conditions : — 

a. Both wires of the circuit must have substantially the same resistance. 

b. Both wires must have substantially the same electrostatic capacity. 

c. Both wires must have substantially the same insulation resistance. 
Overhead Circuits on JPoles. — The above three requirements mean 

practically that both wires must be of the same material, the same length, 
have the same methods of insulation, be carried on the same poles (or in the 
same cable), and in most cases should be on the same cross-arm, and always 
adjacent to each other. 

Electrostatic capacity is treated in the chapter on conductors. 

Mutual- and self-induction are also treated in the chapter on conductors, 
but there are some points applying especially to telephone circuits that will 
be mentioned here. 

The telephone is so sensitive that unless care be taken to prevent it, 
the induction from neighboring lines will produce noise and " cross-talk." 
Therefore, both lines of the circuit must be balanced in relation to adjacent 
lines, so that induction from them may be neutralized. 

This is usually accomplished by transposing the two wires of a circuit at 
certain intervals along the line, the frequency of such transposition varying 
according to the number of circuits on the line and the length of line. On 
the main long-distance lines it is usually done every quarter of a mile. 

The following cuts show the methods of transposition used in the United 
States and in England. 



1300 r 


1300 


n 


1300 FT 




u 


PPER CROSS 
















\ | 






















» | 
























r 






































" 1 








































A £ 


c 






* 


3 










ARM 
























13 > 












































x 




















































































I ! - 




: 






: 






4 1 . 


































Fig. 19. Transposition of 

Metallic Circuit. 



Fig. 18. 



In American practice if more than two cross-arms are used, odd-numbered 
arms are transposed as the upper arm in Fig. 18, and even-numbered arms 
are transposed as the lower arm in Fig. 19. 

In England it is sometimes the practice to change the position of the wires 




552 TELEPHONY. 

at each cross-arm, so that in four spans two wires of a circuit make a com- 
plete twist about each other. 

Aerial cables for telephone circuits are generally made up of No. 18 B. 
and S. copper wire, insulated with rubber to £</' '. 

The wires are twisted in pairs, and laid up into a cable containing the 
number of wires required. Each layer is taped, and the whole is wrapped 
with two strong tapes impregnated with a preservative compound, and laid 
on in reverse layers. 

In modern practice lead-covered dry-core cable is frequently used for aerial 
cable with very successful results. The lower cost and improved electrical 
conditions are substantial arguments in its favor. The chief disadvantage 
is the weight of lead-covered cable as compared with rubber. ' 

"llndergTOund Circuit*. — For many years after the introduction of 
the telephone the difficulties of working throu gh 
underground wires seemed insurmountable. 
The electrostatic capacity of the underground 
wires of early days was so much greater than 
that of overhead circuits as to materially in- 
terfere with telephonic transmission. In late 
years, however, the methods of insulation have 
been so much improved that many thousands 
of miles of telephone wire are now under 
Fig. 20. English method of ground ; and it may be said that underground 

of Transposing Metallic construction of telephone circuits is the gen- 
Circuit, eral rule in large cities, and is rapidly being 
adopted even in small towns. 

The electrostatic capacity of a submarine conductor is twenty times that 
of an overhead copper wire of equal resistance ; and the etectrostatic capa- 
city of the early forms of paraffined-cotton insulated cable was about twelve 
times as high as tbat of an overhead copper conductor, 104 mils diameter ; 
but the underground conductor, being of much smaller cross-section, has a 
higher resistance, about seven times that of the overhead wire in the case 
above cited. 

Underground Cables. — The standard type of cables for telephone 
work contains four hundred insulated wires, twisted in pairs with about 
"three-inch lay ; and the pairs are cabled in reversed layers, forming a cable 
about 2 inches diameter. The cable is always enclosed in a lead pipe with 
walls g inch thick, and for the size here under consideration about 2\ to 2£ 
inches diameter. 100-pair and 50-pair cable, and various smaller sizes, are 
used for distribution. Originally 50-pair was the standard size ; it was later 
replaced by 100-pair, and now 200-pair has practically become the standard 
cable for main routes. 

Cables are often made of other sizes, sometimes of 500 and even of 600 
wires ; but such large cables are difficult to handle, and 100-pair is the size 
most generally used in large cities. 

The insulationof cables is nowmostly of drypaper loosely wound on thewire. 
This method of construction secures a low capacity and a high insulation as 
long as the lead covering remains intact, preserving the dryness of tbe paper. 

Tbe standard size of copper wire for telephone cables is now No. 19 B. and 
S., which has a resistance of about forty-five ohms per mile. 

The average mutual electrostatic capacity is about .085 microfarad per 
mile, and runs as low as .07 microfarad per mile. 

The insulation resistance of ail conductors should exceed five hundred 
megohms per mile, after being laid and connected to the cable heads ; and 
in practice this resistance is nearly always much higher, often several thou- 
sand megohms per mile. 

The lead covering of underground cables is nearly always alloyed with 
three per cent of tin ; and in many cities where the gases are destructive to 
the lead, a covering of asphalted jute is served outside the lead. 

Submarine telephone cables are usually made up of stranded conductors, 
seven No. 22 B. and S. wires, insulated with rubber compound to 3 \inch. 

The cores are twisted in pairs the same as the paper insulated underground 
conductors, and cabled together much in the same way. Ten pairs of con- 
ductors is the usual limit for a submarine telephone cable. The cable 
formed by the cores is served with hemp, and armored with galvanized iron 
wires, the iron being protected by a layer of hemp soaked in a pitch com- 
pound. In situations where the risk of damage by anchors, etc., is not great 
dry core cables are now used for river crossing. The cable is iron-armored 
over the lead sheathing. 



THEORY OF THE MAGNET TELEPHONE. 



653 



lightning- and Current Arresters. — Telephone lines need pro- 
tection from : 

a. Lightning. 

b. Crossing with heavy currents that will immediately burn out the in- 
struments. 

c. Crossing with " sneak" currents, or currents feeble enough not to burn 
out at once, but by gradual or slow heating cause the destruction of the 
instruments or parts of them. 

A simple fuse wire would afford ample protection in most cases but for 
the danger that it will be replaced, when blown, by a copper wire. 

The fuse at the outer terminal of an underground cable is usually set to 
blow at eight amperes. 

A style of protector now extensively used, especially to protect the central- 
station instruments, is the one shown in the following cut. It has an air- 
space cut-out that blows if pressure on the circuit reaches 300 volts ; and a 
"sneak" current arrester that will ground the line within thirty seconds, 
under a steady current of .3 ampere. 

The air-space cut-out consists of two blocks of carbon, separated by a thin 
strip of mica, with a perforation in the centre. The upper carbon block has 
a drop of fuse-metal let into its lower face, which completes the short circuit 
when the current sparks across the space. 

The lower block rests on a metal strip that is grounded, and the upper 
carbon block is held in position by a spring connected to the line. 

The sneak current-arrester is a small spool of fine German-silver wire, 
having a resistance of 28 ohms. 

In the centre of this spool is a metal pin, which is normally prevented from 
passing clear through by a drop of fuse-metal, but which is released when 




Fig. 21. Combination protector. A, 
line-post ; F, instrument post ; B, 
German-silver spring ; CC, carbon 

blocks ; M, mica sheet ; S C, sneak Fig. 22. Plan of Combination Pro- 
coil ; P, releasing-pin ; G, ground- tector. 
ing-strip ; D, ground wire. 

the drop of fuse is melted by the heating of the coil by a foreign current, and 
allows the lower spring connected with line to fly up, and make contact with 
a ground strip. 

Notes on the Installation and maintenance of Tele- 
phones. — The subscriber's telephone should be placed in some location 
out of the usual route of office traffic, and on a solid wall or where it may be 
free from vibration. 

Use No. 18 B. and S. rubber-covered wire for connection to outer circuits, 
unless wires are to be much exposed, when it is better to use No. 16 B. and S. 
The rubber on No. 18 should be at least -^ thick, and on No. 16 at least ^. 

Following the rules of the National Conference of Underwriters (see index 
for insurance rules) will insure a good job ; and as they must be followed, 
it is hardly necessary to give other directions. 

Instruments should be periodically inspected, and all parts should be kept 
clean and bright. 

Go over all connections and binding-posts and see that all are tight, also 
that all screws are tight. 

Dirty contacts and frayed cords often cause much trouble. 

Examine the receiver by unscrewing the ear-piece. The diaphragm should 
not be bent or dirty or rusty ; the pole-piece should be clean, and the top 
should be 3 V inch from the diaphragm, no more, no less ; if it is farther 
away from the diaphragm, the field will be too weak, whereas if much 
nearer, the diaphragm is liable to stick. A good test for strength of magnet 
is to see if it will hold up the diaphragm by its edge. 



£54 TELEPHONY. 

In the magneto bell keep all contacts clean and bright, especial attention 
being givento those of the automatic switch and shunt. 

Gearing and armature bearings should work freely and be occasionally 
oiled. 

The bells should ring clearly, and when ringing dull are probably loose at 
centre. 

Short circuit the bell binding-posts and turn the crank ; the bell should 
ring. Place a resistance of several thousand ohms between bell and gen- 
erator, and the bell should then ring when crank is turned. A generator 
may be strong enough to ring its own bell on short circuit, and yet not do it 
through resistance. 

It is, however, of the most importance that the generator be capable of 
ringing the distant bell, or of throwing the drop at the central station. 

If the bell is known to be all right, and will not ring on short circuit, then 
the fault will be in the generator armature, and may be caused by a broken 
wire or a bad contact. If its contacts are platinized, clean with unglazed 
writing-paper ; if not platinized, use emery paper. 

Short circuit the binding-posts of the transmitter, then tap on the mouth- 
piece or diaphragm of the transmitter, and notice quality of the " side-tone," 
which will enable the inspector with some practice to judge of the condition 
of the transmitter and battery. 

In the Blake transmitter, the rubber band under the diaphragm, the pad, 
and the sleeve must be soft and elastic, and the rubber ring encircling the 
diaphragm must not stick to the casting. 

The platinum spring should touch the diaphragm only with its point. 

The platinum spring and that carrying the carbon should both be tightly 
clamped to the support. 

The contact between the platinum point and the carbon button must be 
clean ; and, as the platinum tends to dig into the carbon and to roughen 
itself, it is highly important that the platinum point be smoothed and bur- 
nished, and that the carbon be rubbed down with emery paper, giving the 
final polish with a clean piece of paper. The platinum point, if not too 
rough, can be polished with unglazed writing-paper. 

Make final adjustment with the bottom screw on the iron support. Test 
results with side tone until tho talk is clear. 

If the talk has a hollow sound, weaken the damper and slip. 

If the volume is poor, loosen the adjusting-screw, stiffen the damper, and 
see that the platinum point rests well against the diaphragm. 

If the sound is broken and confused, give the platinum spring more " fol- 
low" to the carbon button, and see that the diaphragm is firmly clamped 
on the rubber ring, and that there are no inequalities in the ring. If the 
sound is scratchy, clean the platinum and carbon, and see that the platinum 
spring is not twisted. 

A weak battery will give a weak transmission, as will also a high resist- 
ance in the primary circuit. 

Frying and buzzing sounds may be caused by loose battery connections or 
dirt on the carbon button. 

A bent diaphragm will give a metallic sound to the transmission. 

There is no adjustment to the solid-back; and its efficiency depends on its 
having been properly set up at first, and on the condition of the battery and 
its circuit. 

The good working of granular-carbon transmitters depends mainly on the 
battery. If the battery power be too low, the transmission will, of course, 
be weak ; but if it be too high, the transmitter may be overheated, which 
will injure it. 

Two cells of Fuller battery giving about 4.2 volts, or two cells of storage 
battery giving about 4 volts, are generally used with the solid-back instru- 
ments. 

The resistance of the primary circuit is very low when the transmitter is 
at rest, being for the transmitter itself about 1 ohm ; the current may then 
be 2\ to 3 amperes, and the heating may produce packing. 

"When the transmitter is spoken into, the resistance immediately rises to 
about 10 ohms, and the current decreases to .G amperes or less. 

Below is quoted from " Webb " the methods of locating trouble in a 
telephone. 

" When a telephone will not work, the trouble may be either in the line, 
the inside wiring, or in the instrument and its connections. If, on short- 



TELEPHONE SWITCHBOARDS. 655 



circuiting the instrument at the top binding-posts the bell rings and side 
tone is obtained, the instrument is all right. The inside wiring should 
then be tested by short-circuiting the wires if a metallic circuit, or attach- 
ing a temporary ground if a grounded circuit, at the point where the line 
enters the building ; if the bell then rings, the trouble is in the line, and 
must be found in. the ordinary way. If the bell does not ring, the fault is 
in the inside wiring, and can soon be traced out. If no side-tone is obtained 
at the first test, the instrument is at fault. Either the receiver or a detector 
galvanometer may be used in locating the defect. The receiver is most 
convenient, and it should be tested first by connecting it directly to the bat- 
tery ; if a good click is heard, it is all right ; if not, there may be a broken 
wire in the receiver, or the diaphragm may be out of order. If the receiver 
is good, the primary circuit should be tested by opening it at one of the con- 
nections, the automatic switch being up, and trying for current either with 
the receiver or by testing. If no current is found, the trouble may be a 
broken or disconnected wire, loose binding-post, corroded connection, bat- 
tery dry or zinc eaten off ; the automatic switch may have a bad contact 
through rust or dirt, or bent or loose springs, or broken wire ; the transmit- 
ter may have a broken wire or cord, or may be open at the variable resist- 
ance through bad adjustment or lack of carbon. All the various paths for 
the current in the primary circuit should be traced out from one pole of the 
battery back to the other, and the trouble will quickly be found. If the 
primary circuit tests O.K., the trouble must be in the secondary circuit ; 
and this can be tested by connecting one terminal of the battery to one bind- 
ing-post of the telephone and touching the end of a wire joined to the other 
terminal to various points in the secondary circuit, beginning with the second 
binding-post of the telephone. When a click is heard in the receiver, the 
trouble lies between the point just touched with the wire and the second 
binding-post of the instrument. 

The inspector's kit should contain the following tools and material : 

Pair cutting pliers, 

Pair long-nose pliers, 

Warner Battery gauge, 

Tack-hammer, 

Screw-driver, 

Soldering lamp and iron, 

File, 

Dusting brush, 

Coil of insulated wire, 

Rubber tape for covering joints, 

Candle for examining instruments, 

Solder and soldering fluid, 

Small bottle of oil, 

Trimming-knife, 

Box containing screws, staples, washers, nuts, etc., 

Chamois skin, cloth, and polishing paste, 

Spare parts of instruments, such as transmitter and receiver diaphragms, 
cords, hinges, bell-cranks, gongs, rubber bands, dampers, clips and springs, 
carbon buttons, and granulated carbon. 

The small articles are conveniently carried and kept in good order by using 
small round tin boxes to contain them. A separate stout bag should be 
used for battery material, and should contain a number of spare zincs and 
carbon plates or porous cups complete, a supply of sal-ammoniac, etc., a 
strong knife, a sponge, and a quantity of cotton rags or waste. 

The author feels it is necessary to offer some apology for having confined 
the foregoing text so largely to telephone instruments used by the Bell Com- 
pany only ; but principles only are meant to be treated, and there is little 
available data that would serve to make those principles plainer. Many of 
the so-called independent instruments are well designed and constructed, 
and are gradually making headway. The same methods of test and connec- 
tion in general apply to one as well as to the other. 

TDLEPHOIVE IWITCHBOARD§. 

The subject of switchboards will be treated only as to diagrams showing 
the general principles on which they are constructed. They differ much in 
details, and one company at least is carrying on a quite extensive business 



656 



TELEPHONY. 



with an automatic switchboard having no operator whatever. No descrip- 
tion is at this time available which does justice to the exceedingly ingenious 
instrument that makes the connections automatically between any two sub- 
scribers. 

Many improvements in detail have been introduced, and are continually 
being brought out, such as self-restoring drops, luminous indicators in place 
of drops, and various other devices which cannot be mentioned here. 

multiple Switchboard. — The multiple switchboard is in use in most 
of the large offices, and, while very complicated in practice, is simple in 
theory, and is designed to enable the operator to be independent of other 
operators, and to reach each subscriber's line without excessively long cords. 
The board is divided into sections, each being of such a size that an operator 
can reach either end, and yet three operators may work at the board with- 
out inconvenience. 

Every subscriber's line has a spring-jack at every section, but the drop or 
other visual signal is on one section only. There are usually 200 drops on a 
section; therefore when a subscriber calls "central," the operator inserts 
her plug in the spring-jack of the subscriber, learns with what number he 
wants to be connected, then connects one end of a cord from the calling 
subscriber's jack to the one he called, as the number called for has a jack 
on every section. The following diagram shows in simple form the connec- 
tions for three subscribers' circuits for three sections of a multiple circuit 
board. This diagram (Fig. 22a), as are those following, is from an article 
in the American Electrician by Kempster B. Miller. 

Line I. 




Line 2. 



Line's. 



This form of board is open to many 
defects, and is being replaced by an- 
other form to be next described. The 
series multiple board, as the above is 
sometimes called, has all the spring- 
jacks of a subscriber's line in series, 
and a weak spring or a particle of 
dust may open-circuit one of the 

jacks and put the line out of use. ^a i i p IG 22a 

The circuits are also liable to unbal- 
ancing. 

Branch Terminal Mriltiple- 
JBoard. — This is a multiple-board 

devised to overcome the defects of the series multiple-hoard previously de- 
scribed. The general distribution of circuits is the same, but the spring- 
jacks are connected to the subscriber's line in multiple instead of in series. 
There is a common ground-wire for all sections, and there is also a third 
wire through each section for each circuit of a subscriber. This line is so 
connected through the drop magnet as to automatically restore the shutter 
when connection is made to the calling subscriber's jack. 

The following diagrams (Figs. 226, 22c) give the scheme of the connec- 
tions. 

Express System. — As the number of subscribers increases, the multi- 
plicity of circuits, jacks, and connections increase as the square of the num- 
ber on all multiple-boards. 

Messrs. Sabin & Hampton of San Francisco devised a system that has 
been in use several years in the San Francisco office. It is much simpler 
than the multiple system, but not so handy to operate. Each subscriber's 



SWITCHBOARDS. 



657 



line has one line-jack, which is on a section of board which may he termed 
B boards. The' B" boards are divided into sections of 100 lines each, 
with an operator for each section. Another set of boards, called "A" 
hoards, are used as a sort of clearing-house, through which all connections 
from suoscnber to subscriber are made. Trunk-lines lead from the " B " 
boards to the "A" boards, and an order-wire connects the "A" board 
operator with the " B " board operators. When a subscriber calls the " B " 
operator on the section on which the calling subscriber's line-drop happens 
to be situated merely plugs a trunk-line into the subscriber's spring-jack 
The "A" operator inserts her listening-plug in the trunk-line iust con- 
nected, and asks what number is wanted. She then calls through the order- 
wire to the "B" section on which the required number is situated, asking 



y . Line I. 




Fig. 22c 



Ca "%Ury^ 



1 w 

Lj u 



r~"~-H j h 'Subscribers-Lines. 






that operator to plug a trunk-line in on the number required, which she 
does, and answers back giving the number of the trunk-line she proposes to 
use ; and the "A" operator then connects the ends of the two trunk-lines 
by a multiple cord, as on the multiple-board. The process would seem to 
be complicated, but is said not to cause unusual delays. 

No magneto bell is used ; the subscriber merely removing his telephone 
from its hook operates the calling drop, which immediately restores itself 
when the trunk-line is plugged 
in or the subscriber hangs up 
his telephone. The drop signal 
also operates at once, should the 
"B" operator pull the trunk- 
line plug before the subscriber 
has finished. One small storage 
battery is sufficient for a large 
exchange; and the entire plant, 
— boards, subscribers' instru- 
ments, and all, — is much less 
expensive than those of the or- 
dinary multiple type. 

The diagrams (Figs. 22d, 22e) 
show the scheme of connections 
in the Express System; the first 
one showing the subscribers' 
lines and their connections to 
the "B" boards, while the 
second diagram shows the ' ' cen- 
tral" connections. ~FiGc. 22d. 






4?1 



^ 



^L. 



(5,38 



TELEPHONY. 



Subscriber's Line 




C01WM[0]¥-BATTJEIIY SYSTEM:. 

The common-battery system, as its name implies, is a centralized energy 
system ; i.e., the transmitter and signalling batteries, or sources of energy, 
are all located at the central office or exchange. This centralization has 
numerous advantages : batteries at each station are done away with, thus 
lessening the inspection and maintenance charges ; hand generators are not 
required at each station, thus decreasing the investment ; and the apparatus 
at stations is made much more compact and neater. The power-plant at 
the central office is, however, more expensive to instal and maintain than 
in the magneto system. The service is quickened, and the labor on the part 
of the subscriber is diminished. 

The underlying principle of the common-battery system is the insertion of 
a battery into the line connecting two stations, the battery being a part of 
the cord circuit completing the connection, between the stations, at the 
exchange. 

The line from the station enters the exchange, passes through the contacts 
of a cut-off relay, then one side of the line passes directly to ground, while 
the other side passes through a line relay, and battery to ground. A line 
lamp signal, an auxiliary relay and battery, are connected through the con- 
tacts of the line relay, the auxiliary relay controlling a pilot lamp signal. 
The cord circuit contains a repeating coil and battery. Supervisory relays, 
controlling lamp signals, are placed in both the answering and the calling 
sides of the cord circuit at the exchange. The calling side also contains a 
combined ringing and listening key, or separate keys. 

The operation of this system is briefly as follows : Nominally the receiv- 
ers are on the hooks, and the line-circuits are open. Removing the receiver 
from the hooks closes the line circuits through the contact of the hook- 
switch, current then flowing through the line from the central office. This 
flow of current energizes the line relay, closes its contact, thus lighting the 



PARTY LINES. 659 

line lamp signal, and closing the contacts of the auxiliary relay which in 
turn lights the pilot lamp. The pilot lamp acts as a safeguard in case the 
line lamp is broken, and also gives the supervising operator an indication as 
to the line operators' punctuality in answering calls. The lighting of the 
line lamp indicates that a station is calling. The operator takes the answer- 
ing plug of the cord circuit and inserts it into the jack of the calling line. 
This introduces grounded battery through the sleeve of the plug, energizes 
the cut-off relay, opens the circuit of the line relay, and thus extinguishes 
the line and pilot lamp signals. Having ascertained the number called for, 
the operator inserts the calling-plug into the proper jack, and rings the called 
for station. As long as the receiver at the called-for station remains on the 
hook the supervisory relay in the calling side of the cord circuit is not en- 
ergized, and the supervisory lamp is lighted. As soon as the receiver is 
removed from the hook the supervisory relay is energized, and the lamp is 
shunted out by a low resistance, and thus extinguished. 

When neither of the supervisory lamp signals in the cord circuit gloAvs, 
the operator knows that both receivers are off the books. The operator 
can supervise the conversation, if necessary, by means of tbe listening-key. 
If neither station hangs up its receiver, the supervisory relay armature, is 
released, and the corresponding lamp signal glows. When both lamps glow, 
the operator knows that both stations have hung up their receivers and that 
the connection is at an end, whereupon she disconnects by removing the two 
plugs from their jacks. If during the connection one station wishes to 
attract the attention of the operator, he can do so by moving the receiver 
hook up and down, thus causing the supervisory lamp signal to flash. 

Lamp signals as above described are much used in the larger exchanges, 
and are rapidly coming into more extended use. The magnetic signals are, 
however, largely employed in the smaller exchanges. 

In furnishing many lines with currents from the same battery, precautions 
must be taken to eliminate cross-talk. This is accomplished by using sto- 
rage-batteries of large capacity and very low internal resistance, and of cop- 
per bus-bars of large cross-section. The multiple board is largely used, 
usually of the divided type. A good description of the common-battery 
system is to be found in Miller's " American Telephone Practice." 



PARTY HIES. 

Until 1896 or 1897 no party-line system seems to have been invented that 
was at all satisfactory for regular use ; but the advent of the " B.W. C." sys- 
tem, put forward by the Bell Co.'s, has changed all that, so that in residence 
districts lines with six or more subscribers are becoming very common ; and, 
as the charge for such installations is materially less than for the direct 
line-system, and only the latest and best instruments with metallic circuit 
are used, the service is equal to the best. 

A good description of the " B. W. C." (Barrett, Whittemore, Craft) system 
has been published in the American Electrician for January and February, 
1899. 

No special systems can be described here except in illustration of prin- 
ciples of Avorking. 

As the telephonic current is undulatory, it is retarded by coils of wire 
having self-inductiOn ; and all such coils connected into the line hinder the 
good working of its instruments. For this reason but few telephones can 
be connected in series and work with any kind of satisfaction, as the self- 
induction of the bell-magnets soon cuts down the transmission below the 
working-point. In practice, telephones for party lines are connected in 
multiple ; and J. J. Carty, of the New York Telephone Co., invented the so- 
called bridging-bell, which enables us to couple up ten to thirty stations in 
parallel. 

The magnet-coils of the bridging-bell are wound with a large number of 
turns of No. 33 B. and S. wire, and measure 1000 ohms resistance. 

The magnets, therefore, have high self-induction, which stops off tele- 
phone currents, but does not prevent the bell ringing. The disadvantage is 
that all the bells ring when any one of them is started ; and it is necessary, 
therefore, to have some code of signals by which calls for different stations 
may be distinguished. 



660 



TELEPHONY. 



The generator armature of the bridging-bell is wound with low resistance, 
so^ as to give plenty of current for ringing the bells. 
The following three diagrams show the bridging-bell and its connections. 





Fig. 24. Polarized Bell with long core 
for Ringer of Bridging-Bell. 



The Bridging-Bell 




Fig. 25. Diagram of Connections of 
Bridging-Bell. 



lOUfft-DIiTAUfCE LOE§. 

In American telephone parlance the term " long distance " has come to 
mean lines of the very best construction, and instruments of the latest and 
best pattern. 

The standard size of wire used on long distance lines is No. 12 N. B. S. G., 
104 mils, hard-drawn copper, weighing 172 pounds to the mile. On the longer 
lines No. 8 wire, 165 mils, weighing 435 pounds to the mile, is used. 30-ft. 
poles are used, set 130 feet apart and 6 feet in the ground. 





Fig. 26. Standard Repeating-Coil. Fig. 27. Diagram of Connections 

of Repeating-Coil. 

Cross-arms are 10 feet long, 3| x 4£ inches. They are placed 12 inches 
apart, secured to the poles by bolts, and supported by iron braces. 

Double cross-arms and transposition insulators are provided on every 
tenth pole ; and at each such pole some of the circuits are transposed in 
order to avoid inductive disturbance. 



DUPLEX AND MULTIPLEX TELEPHONY. 



661 



Great care is taken to keep each side of long-distance circuits balanced ; 
and for this reason all central-office appliances are connected in " bridge." 

For joining local or grounded lines to the long-distance so as not to dis- 
turb the balance, the circuits are connected through a repeater, which is an 
induction coil, well made, and proportioned for the purpose. 

Figs. 26 and 27 show the standard repeating coils, as connected and as 
made up. There is a closed core of tine iron wire, with its ends interwoven 
and spliced after the two coils are wound on as shown. There are 10,000 
turns of No. 30 B. and S. wire wound in four coils, one-half of one circuit 
being the inner half of each coil, the two being connected in series. The 
other circuit is wound outside of these coils, one-half over each side. 

The following diagrams show the method of connecting grounded, local, 
and long-distance lines together through repeaters. 




ji=Kl 



LONG DISTANCE 
METALLIC LINE 



FlQ. 28. Long-distance circuit connected to grounded circuit through 
repeater coil A. 




I\ 



Fig. 29. 



Two distant grounded circuits connected through repeating coils 
A and B to a long-distance metallic circuit. 



l*=Qf 



>=d 



Fig. 30. 



Local metallic and long-distance metallic circuits connected 
through repeating coil A. 



DUPLEX .AJtfI> MULTIPLEX TELEPHONY. 

The following diagrams show a method of duplexing and multiplexing tel- 
ephone lines invented by Frank Jacobs. They are interesting, but have not 
yet proved to be of great practical use. 

The duplex system is an arrangement by Wheatstone bridge, with resis- 
tances Rj, R 2 , R 3 , Pv 4 , connected as shown. Those at either end must be 
equal to each other, but the two ends need not be the same. 

These resistances must be greater than that of the line in order that the 
currents from T 3 and T 4 may pass along the line rather than around the 
coils. The condensers may be placed in shunt to the coils in order not to 
retard the current, so that T x and T 2 may work better. 




Fig. 31. Duplex Telephony. 



662 



TELEPHONY. 



The second diagram shows the method of multiplexing; but it is easily 
seen that 1\, T 2 , T 3 , T 4 , will not work well owing to the resistances interposed. 




Fig. 32. Multiplex Telephony. 



§IlHrLTAHEOU§ TELEGRAPHY .4»'W TEL- 
EPHOSY. 

A system of simultaneous telephony and telegraphy is extensively em- 
ployed in the United States, and is an improvement upon the system invented 
by Van Rysselberghe of Belgium, the system being often called by his name. 
The figure, taken from Maver's "American Telegraphy," gives a general 
idea of the working of the system. 




Fig 33. 



It consists of a combination of telephone and telegraph apparatus with 
condensers and retardation or impedance coils so arranged that the Morse 
signals do not react upon the telephone apparatus and the telephone cur- 
rents do not react upon the telegraph apparatus. The letters attached to 
the component parts of the figure are self-explanatory. The retardation 
coils in the line circuit keep back the telephone currents, and the condensers 
in the telephone legs keep back the Morse currents. 



INTERIOR TELEPHONE SYSTEMS. 



663 



INTERIOR TELEPHONE SYSTEMS. 

Condensed from articles by W. S. Henry in Am. Elec. — 1900. 

The systems considered may be divided into series party lines, bridging 
party lines, intercommunicating systems, and small central switchboard 
systems. As the last system differs practically only in size from the regular 
central station system no description of it will be undertaken here. In 
these systems either magneto or microphone transmitters may be used, and 
the signaling apparatus may be either magneto bells and generators or the 
common vibrating bell and battery. 

Where microphone transmitters or vibrating bells are employed, the 
batteries may be distributed at the various stations or, in some cases, all 
concentrated at one place. It is generally desirable, although not really 
necessary, so to arrange the circuits that the bell at the calling station, or 
the home bell as it is called, should ring when calling up another station. 
This assures the person signaling that his own circuit and probably the 
whole system is in working order, and that his call is being transmitted to 
the desired station. 

One of the simplest telephone systems comprises magneto instruments 
connected in series in one line. Fig. 34 shows an arrangement of this kind 
requiring at each station two magneto instruments ; T is the transmitter 
and R is the receiver. An ordinary vibrating battery bell, V, a battery, B, 
of two or more cells, and a hook switch, H, complete the equipment. When 
the receiver, R, is hanging on the hook, the line is connected to the lower 
contact ; when the receiver is removed, a spring pulls the lever up against 
the contact, b. The smaller auxiliary switch, I, is arranged to normally 
rest on the contact, c. It may be pressed down upon d, but when released 
it should be returned to c by a stiff spring. 



TF~ 



j] 



l~f 



~WT] 



Fig. 34. Series System with Magneto Transmitters and Signaling 
Batteries. 

In Fig. 35 a very similar arrangement is shown, the only difference being 
the use of magneto generators, G, in the place of the signaling batteries, 
B, of Fig. 34, and the substitation of magneto bells for the simple bells used 
in the first system. The signalling key, K, has only the upper contact, to 
normally short-circuit the generator, G, as indicated in the sketch. Some 
magneto generators are provided with an automatic arrangement on the 



RTF! 

6TATW!lt * 


8TATION2 ^ ^-= p. 


UTF~ 

8TAT10N 8 ,* ,» 


_ fi -^J 


jXr 



Fig. 35. Series System with Magneto Transmitters and Generators. 

spindle which short-circuits the armature of the magneto whenever the 
spindle is at rest. The act of turning the handle of the magneto removes 
the short-circuit and allows the induced current to pass out to the line. 
When this type of magneto is used, the push button, K, is, of course, 
unnecessary. 



664 



TELEPHONY. 



The arrangements described are known as series party lines, meaning that 
all of the stations connected up are in series with each other. As intimated 
above, when this arrangement is used even for a small number of stations, 
the bell magnets should have as low resistance and as few turns of wire on 
them as possible, in order to reduce the impedance of the circuit; and the 
generators should be wound with rather fine wire, because the current gen- 
erated must pass through all of the bells in series. 

In order to avoid forcing the talking current through the magnets of the 
signaling bells, the latter may be " bridged " directly across the circuit, as 
shown in Fig. 36, in which case the bells may be wound for high resistance 
and impedance so that the talking currents will be turned past them. 



pnn 



t.^Y 




[H~l 



,_? 



Fig. 36. Bridging System, Avith Magneto Transmitters and Generators. 

In Fig. 36, three different methods of bridging are shown. At Station 1 
the bell is removed entirely from the circuit when the receiver hook is up ; 
at Station 2 the bell remains constantly across the circuit in series with the 
transmitter and receiver, but when the hook is up it is short-circuited by 
the hook and its upper contact through the wire, a ; at Station 3 the bell 
remains permanently connected across the circuit, and when the receiver 
hook is up the transmitter and receiver are connected in parallel with it. 





r+p 



U 



"#* 



Fig. 37. Series Systems with Microphones and Batteries. 

Fig. 37 shows the simplest method of using microphone transmitters. The 
instruments are a transmitter, T; an ordinary receiver, R; a vibrating 
bell, V, and one or two separate batteries at each station. The battery, B, 
is used only for ringing the bells ; the battery M. B., only for operating the 
microphone transmitters, and the battery IJ, for both purposes. In this 



6TATI0W 1 

" H 

TfcT 


> 


STATION 1 


) 


STATION 3 

yd 

n2r 



FIG. 38. Series System with Microphones and Magnetos, 



INTERIOR TELEPHONE SYSTEMS. 



665. 



arrangement, as well as in the one shown by Fig. 3S, the microphones, 
receivers, and microphone batteries are directly in series with the line, no 
induction coils being used. 

Instead of vibrating bells and batteries for ringing, we may use a polar- 
ized bell, C, and a generator, G, as shown in Fig. 38. In such an arrange- 
ment the talking current must pass through all the polarized bells except 
those at the stations where the receivers are removed from the hooks. 





+j* 




Fig. 39. Bridging System with Microphones and Magnetos. 



A better arrangement is to use high-impedance bells bridged across the 
two-line wires, as shown in Fig. 39. The generator, as explained in connec- 
tion with Fig. 36, is normally on open circuit. 

Three bridging methods are shown. At Station 1 some of the current 
from the battery, M.B., can flow through the bell when the receiver is off 
the hook, but this will do no harm ; in fact, it may be beneficial, for it 
allows a larger direct steady current to flow through the microphone. The 
fl actuations in the current produced by the microphone cannot pass 
through the bell-magnet coils, but will pass through the line circuit on 
account of the lower impedance of the latter. At Station 3 the bell is cut 
out when the hook switch is raised, and at Station 2 both the generator and 
bell circuits are cut off by raising the hook. An extra contact, d, is 
required at these two stations, but on the other hand, there are two bells 
less across the circuit to form shunts or leaks for the current when two 
parties are conversing. On the whole, the arrangement at Station 3 is the 
best of the three. 

Fig. 40 represents a series party system (corresponding with that which 
was shown at Station 1 in Fig. 37) in which a battery, £, and vibrating bell, 
V, are used for signaling, and an induction coil, I, is added to the speaking 
apparatus. The primary of the induction coil is in series with the micro- 
phone transmitter, T, and its battery, MB., and the secondary is in series 
with the telephone receiver and the line. 

The connections at Stations 1 and 2 are identical ; when the receiver 
hook, H, is down the talking instruments are entirely cut out, and when it 




Fig. 40. Series Party System, with Induction Coils and Signaling 
Batteries. 

is up the signaling key, battery and bell are thrown out of circuit and the 
main circuit passes through only the telephone receiver and the secondary 
of the induction coil. At Station 3 the connections are different ; when the 
receiver hook is down the telephone receiver and secondary of the induc- 
tion coil are merely short-circuited, while the transmitter, its battery, and 



666 



TELEPHONY, 



the primary of the induction coil are open-circuited. When the hook is up, 
the talking instruments are connected up for service and the signaling part 
of the apparatus is short-circuited. Fig. 41 corresponds with Fig. 40, except 
that magneto-generators, G, and magneto bells, C, have been substituted in 
the place of the signaling battery and vibrating bells shown in Fig. 40. The 
station connections correspond also, the receiver hook, B, at Stations 1 
and 2 being arranged to throw in and out of circuit the talking apparatus 
and the signaling apparatus, while the hook at Station 3 merely short- 
circuits the signaling apparatus or the receiver circuit, according to its 
position. This arrangement is the preferable one of the two, for the reason 
that faulty switch contacts at the receiver hook will not open the circuit, 
so that there will always be a continuous line through which one may 
signal. 




Fig. 41. Series Party System Using Induction Coils and Signaling 
Magnetos. 

A simple system installed where there was considerable noise, dirt, and 
vibration, is represented diagrammatically by Fig. 42. Here, there are three 
line wires, a, b, and c, the line c forming a common return for both the 
signalling and the talking circuits, a and b, on which the apparatus is ar- 
ranged in series. In this system the talking line is never open-circuited, the 
telephone hook, H, serving to merely short-circuit the receiver and the 
secondary of the induction coil when down, and to remove the short-circuit 
and close the local circuit of the transmitter and induction coil primary 
when up. It is obvious that the middle line wire, c, gives a free path to the 
talking current, instead of its being forced through the signaling bells. Such 
an arrangement facilitates the separation of the signaling and talking ap- 
paratus, so that the call bells can be located where they can be easily heard, 
while the transmitter and receiver may be put in a sound-proof closet. The 
disagreeable noises due to induction from lighting or power circuits may be 
overcome by using a twisted three-conductor cable between stations. Such 
an installation is greatly superior to the series system shown by Figs. 40 
and 41. 




Three-wire Series Party System. 



Fig. 43 shows a series system in which one battery is used both for signal- 
ling and for talking. In this system the connections are alike at all stations ; 
when the receiver hook, H, is down and the signaling key, /,is up, there are 
included in the line circuit only the vibrating bells. Depressing the signal- 



INTERIOR TELEPHONE SYSTEMS. 



667 



irig key I, puts the battery in the line and causes all the bells to ring. It is 
preferable to have the batteries so connected up that if two or more signal- 
ing keys should be depressed at once the batteries will agree in polarity. 
When the receiver hook is up the battery is connected in series with the 
transmitter and the primary of the induction coil, while the signaling key 
and bells are thrown out of circuit and the telephone receiver and secondary 
winding of the induction coil are included in the line, as shown at Station 3. 




Fig. 43. Series Party System using only Battery at each Station for both 
Talking and Signaling. 

In this, as in previous series systems, with the exception of Fig. 42, the 
talking current must flow through the signaling bells at idle stations. The 
advantage of the system is obviously that it eliminates half the batteries, 
only the one battery being used at each station for both signaling and talk- 
ing. As in all series systems where vibrating bells are used, the vibrators, 
should be short-circuited on all bells except one. 

The best method for connecting a large number of telephones on a single 
system where only two line wires may be used is to bridge them, as shown 
in Fig. 44. The dots A and A', represent the binding-posts of each complete 
outfit. The bells are permanently bridged between the two line wires at 
Stations 1, 2, and 4, irrespective of the position of the receiver hooks. The 
magneto generator is also bridged across the two line wires in an independ- 
ent circuit, Avhich is normally kept open either by a push-button, 1c, or by an 
automatic device on the magneto spindle. 





y# Hajr 





Fig. 44. Bridging Party-Line System; Three Arrangements of Station 
Instruments. 

At Station 3 the magneto generator is bridged permanently across'the line 
as in Stations 1, 2, and 3, but the bell is connected across only when the re- 
ceiver hook is down, being thrown out when the hook is up. At Station 5 
the bell and generator are bridged across the line wires when the receiver 
hook is down, and are cut out entirely when it is up. At all of the stations 
a third bridging circuit includes the receiver and the secondary winding 
of the induction coil in series, this circuit being open when the receiver 
hook is down, and closed when it is up. The hook also closes the local 
transmitter circuit in the usual way when it is up, and opens it when it is 
down. The connections shown at Stations 3 and 5 possess the advantage of 
cutting out their signaling bells entirely when the receiver hooks are up, 
instead of leaving the bells shunted across the line continuously, as is the 
case at Stations 1, 2, and 3. 



668 



TELEPHONY. 



larTERCOOTiiiusricAiiurG systems. 

An intercommunicating system may be defined as a system having three 
or more telephones connected to the same system of wiring in such a manner 
that one may from any station call up and converse with any other station, 
without requiring any central-station switchboard whatever. Intercom- 
municating systems require one wire from each station to every other station 
and at least one more wire running through all the stations. Where vibrat- 
ing bells and one common ringing battery are employed, at least two more 
wires than there are stations are necessary. At each station there must be 
a switch of some kind whereby the telephone at each station may be con- 
nected to any one of the wires belonging to the other stations. Intercom- 
municating systems are very practical and satisfactory up to fifteen or even 
twenty stations ; beyond that, the large number of wires running through 
all stations makes the cost of the system increase rapidly, especially when 
the stations are some distance apart. For a large number of stations well 
scattered, a simple central-station switchboard system is preferable. 

Fig. 45 shows a very common but not a good method of interconnecting a 
number of telephones, where each station is equipped with ordinary series 
bells and magneto generators. Theoretically any number of telephones may 
be connected on such a system, but practical consideration would place the 
limit at about twenty. In this figure there are four stations ; at Nos. 1, 2, 
and 4 the telephone connections are draAvn in full, while at No. 3 is shown 
the telephone outfit as it usually appears. There are four individual line 
wires, numbered 1, 2, 3, and 4, and a common return wire. Thus there is 
one more wire than there are stations, and all these wires run through all 
the stations, each Avire being tapped at each station and not cut. At each 
station there is one ordinary telephone instrument consisting of the usual 
talking apparatus, magneto-generators and polarized bells. BeloAV each 
telephone there is an intercommunicating sAvitch, the buttons of which are 
connected to the respective line wires, and the common return wire. When 
not in use tbe switch at each station should remain on the home button. 



fri 




Fig. 45. Intercommunicating System, with Magneto Signaling Gener- 
ators and Polarized Bells. 



With all the levers in this position, a person at any station can call up 
any other station by moving the switch lever to the button connected with 
the individual line of the station desired, and turning the generator 
handle ; only the bells at the home station and at the station called up will 
ring. The ringing and talking currents pass through only the instruments 
at the stations in communication. After 'finishing the conversation, the 
switch lever at the home station must be returned to its home position, 
otherAvise the system Avill be crippled. 



INTERCOMMUNICATING SYSTEMS. 



669 



In Fig. 46 is shown a method of wiring the intercommunicating switch 
that avoids the principal objection mentioned in connection with Fig. 45, 
that is, the failure to return the switch to the home position does not leave 
the station so that it cannot be called up. Only four stations are shown, 
but the system can be extended to include as large a number as may be 
desirable. The usual telephone sets, consisting of a microphone trans- 
mitter, induction coil, receiver, hook switch, two cells of battery, a series 
magneto-generator and polarized bell, are included in the outfits indicated 
by Tjj T 2 , etc. The inside connections of these telephones are the same as 
shown in the preceding figure. 



Common Return Mr, 




Fig. 46. 

In Fig. 46 one binding-post of each telephone is connected to the common 
return wire, and the other binding-post is connected to both the lever arm, 
s, and the individual line wire belonging to that particular station. 

The home button in this last system is the first on the left and is not con- 
nected to anything ; it is really a dummy button, but it should be there by 
all means, for the lever, s, of the switch should always be returned to it 
when the original calling party leaves the telephone. If all switch arms, s, 
are on the home buttons it will be found that the circuits of all instru- 
ments are open and no bell will ring, no matter what generator is turned. 
If Station 2 desires to call Station 1 it will be necessary to first move the 
switch arm, s, at Station 2 to bixtton 1. 

Fig. 47 is a system similar to that shown in Fig. 46, but arranged for vi- 
brating bells and one common calling battery, CB, in place of magneto- 



.Blllery Wire 
Common Return Wire 





mf* 



Fig. 47. Common Signaling-Battery System, 



670 



TELEPHONY. 



generators and polarized bells. A battery is used at eacb station for oper- 
ating the transmitter. This is probably the best arrangement of batteries 
for such a system where vibrating bells are used. This system requires one 
more wire than that shown in Figs. 45 and 46 where magneto-calling ap- 
paratus is employed; thus there are two more wires throughout than there 
are stations. The calling battery, CB, must be connected to the two wires 
shown, but it may be located at any convenient place. In this arrangement 
only the bell at the station called will ring, the bell at the calling station 
remaining silent. If the bells are not arranged in this manner, the vibra- 
tors on the two bells that happens to be connected in series when making a 
call might interfere more or less with good ringing. Furthermore, it would 
not do to short-circuit any of the vibrators, because there is no telling which 
two stations may be connected together in making a call. 



Battery Wins 

Common Return Wire 






Fig. 48. Common Signaling-Battery System. 

Trouble is experienced with intercommunicating systems similar to that 
of Fig. 47 by reason of the user carelessly leaving the selective switch S, off 
the home button after using the telephone. Fig. 48 shows a method of wir- 
ing such a system which obviates to a considerable extent this trouble. 
Here, the vibrating bell is permanently connected to the home button, and 
the pivot of the switch, S, is connected to the arm of the push-switch, K. 
Any station can still be called up, no matter on what button its switch, S, 
may be left. 






Fig. 49. 



The same system of wiring employed in Fig. 48 is applied to the system 
shown in Fig. 49, in which magneto-generators, G, and polarized bells, C, 
are used in place of the battery and vibrating bells. There is no need of 
having a push button or automatic shunt on the generator, although it will 
do no harm. The generator is normally on open circuit because one of its 
terminals is connected to the under contact of the push switch, K. In order 
to call up a station, the switch, S, is placed on the button belonging to the 
station desired, the push switch, K, depressed, and the generator handle 
turned. Since no common battery is employed for ringing, this system 
requires one less wire through all the stations than the preceding arrange- 
ment, 



INTERCOMMUNICATING SYSTEMS. 



671 



In Fig. 50 is shown an arrangement in which one conveniently located 
common battery, C B, supplies current for ringing and also for all trans- 
mitters. No matter where the lever of the selective switch is left, the bell 
can still be rung, but conversation cannot be carried on until the switch at 
the station called is returned to the home button. This system includes a 
piece of apparatus at each station that has not been required in any of the 
systems previously described, to-wit : the impedance coil E. Where a 
common battery supplies all the local microphone circuits with current in 
systems of this kind, there is very apt to be cross talk between two pairs of 
telephones that may be in use at the same time, in which case the battery 
will be supplying current to four microphones. 



eATTERY WIRE 




Fig. 50. Common Battery System with Impedance Coils. 



The cross talk is due to the variation in the fall of potential along the 
battery and common return wires. 

The cross talk may be greatly reduced by using batteries of very low in- 
ternal resistance, such as storage cells, and making the common return 
and battery wires extra large, that' is, small in resistance, so that the vari- 
able fall of potential through the battery and in these two wires may be 
small. However, it is impractical to make the resistance of these two 
wires low enough, especially where they are of considerable length, to 
eliminate all cross talk. 

Another way to reduce the trouble from cross talk is to insert an impe- 
dance coil in each microphone circuit, as shown in Fig. 50. This makes 
the impedance of each microphone circuit large compared to that of the 
two lines and battery, and in order to get the same current as before in 
each microphone the e. m. f . of the battery must be increased. These im- 
pedance coils reduce the efficiency of the system, but the reduction in 
cross talk compensates for this loss to a great extent. 




*W^ 





Fig. 51. Radial System ; Selective at One Station Only. 



672 



TELEPHONY. 



It sometimes occurs that a system is required to be so arranged that one 
station can call up any one of the others, but the others can call up and 
converse with the first station only. Fig. 51 is a diagram of such a system; 
Station No. 1 or No. 2 can call up station C hy merely depressing the push 
switch Kl or K2, but they cannot call up or converse with each other. 
Station by means of the switch, S, and push, K, can call up either 
Station No. 1 or No. 2. There are only two wires that must run through all 
the stations. There is one wire, however, from Station C to each one of 
the other stations. These wires, Call Wire No 1 and Call Wire No. 2, are 
used only when Station C calls up one of the other stations. One wire 
could be made to answer if there Avas no objection to having all but the 
home bell ring when Station C makes a call. In this case a certain num- 
ber of rings would be necessary for each station except C, and the one 
common call wire would be connected to the signaling key at a, Station C, 
and there would be no need of the switch, S. 

As arranged in the diagram, the push switch, K, is normally open. When 
Station C desires to call Station No. 2, for instance, the switch, S, must be 
turned to button 2 and the push switch, K, depressed. The one common 
battery, B, furnishes current for all ringing and talking. At each station 
there is an ordinary receiver, microphone transmitter, and vibrating bell. 
There is only one bell in circuit when a call is made so that each bell must 
have a vibrator. It makes no difference upon what button the switch, S, 
is left. 

In the systems so far described there is nothing to prevent the intercom- 
municating switch from being left off the home button when the conversa- 
tion is finished and the receivers hung up. 




Fig. 52. Ness Automatic Switch. 



An example of a device obviating this trouble is the Ness automatic 
switch, illustrated by Fig. 52, arranged so that the replacing of the re- 
ceiver upon the hook causes the switch to fly back to its home position. 
In the engraving S is the lever of the selective switch, adapted to be ro- 
tated over the various contact buttons, 1, 2,3, etc. It is mounted upon a 
shaft, A, passing through the front board of the box and carrying a ratchet- 
wheel, E, inside the box. This ratchet-wheel is held in any position to 
which it may be rotated by a pawl, F, and thus prevents the lever S, from 
turning backward. Upon the short arm of the hook lever, H, is pivoted a 
dog, G, adapted, when the receiver is removed from the hook, to engage a 
notch in the pawl, F; when the receiver is replaced, the dog, G, is pulled 
upwards and lifts the pawl out of the engagement with the ratchet-wheel, 
allowing a spiral spring around the shaft, A, to return the switch lever, S, to 
the home button. After raising the pawl out of the notch on the ratchet- 
wheel the dog slips out of the notch on the pawl, thus allowing the latter to 
return into contact with the ratchet-wheel in order to be ready for the next 
use of the telephone. In order, however, that the pawl may not engage the 
ratchet-wheel before the lever, S, has fully returned to its normal position, 



INTERCOMMUNICATING SYSTEMS. 



073 



a second dog, J, is provided which is pressed by a spring so as to occupy a 
position under the pin,£>, carried on the pawl, F, thus holding it out of 
engagement with the ratchet-wheel until the rotation of the lever is com- 
pleted. .At this point a pin on the farther side of the ratchet-wheel pushes 
the dog, J, out of engagement with the pin, j?, and allows the pawl, F, to 
drop into contact with the ratchet-wheel. 




Fig. 53. Common Signaling Battery System ; Individual Talking 
Batteries. 

In Fig. 53 are shown the circuits of a four-station system using one com- 
mon battery, CB, for ringing up the various stations, each station having 
an ordinary vibrating bell, C. The circuits of Stations 1 and 4 are shown in 
full, Avhile those of the intermediate stations, being exactly the same, are 
partially omitted. It will be noticed that the switch lever, S, at each 
station is connected with the line wire bearing the same number as that 
station, by means of the wire, d. Each line wire is also connected at each 
of the stations not bearing its own number with a button on the switch of 




Fig. 54. System having Common Talking and Signaling Battery. 



674 TELEPHONY. 

that station which does hear the same number in the manner pre- 
viously described, by means of tbe wire, e. In this common-battery call 
system two additional wires are run, one being termed tbe " call wire " and 
the other the " common talking wire." The call wire and the talking wire 
are connected through tbe calling battery CB, as shown. It is evident that 
the number of wires passing through all the stations will be two more than 
the number of stations, irrespective of that number. 

If Station 4 desires to call up Station 1, for example, No. 4 will turn his 
switch lever until it rests upon button 1, then a slight pressure upon the 
switch knob causes the switch lever, S, to touch the contact strip, I), com- 
pleting a circuit from the battery, CB, to contact strip, JD, lever, S, and 
button, 1, at Station 4; line wire, 1, wire, d, switch, H, and bell, C, at 
Station 1, and back to the battery through the common talking wire. 
When both subscribers remove their receivers from the hooks, the circuits 
are completed over line wire 1 with the common talking wire as a return. 
At the close of the conversation the receiver is simply hung upon the hook, 
and the automatic mechanical device returns the lever to the home po- 
sition. 

Fig. 54 shows the application of the Ness automatic switch to an inter- 
com muicating system, using one common and centrally located battery for 
supplying both the ringing and talking current. The section, TB, of the 
battery supplies all the microphone transmitter circuits, and the whole 
battery, KB, supplies the current for ringing the ordinary vibrating bells 
that are used in this system. In this arrangement it is evident that the 
number of wires passing through all the stations will in any size of system 
be three in excess of the number of stations. 



ELECTRO-CHEMISTRY. - ELECTRO- 
METALLURGY. 

X L E<J TIIO-C II E Jl IKTIl IT . 

Electrolysis. 

The separation of a chemical compound into its constituents by means of 
an electric current. Faraday gave the nomenclature relating to electroly- 
sis. He called the compound to be decomposed the Electrolyte; and the pro- 
cess Electrolysis. The plates or poles of the battery he called Electrodes. 
The plate where the greatest potential exists he called the Anode, and the 
other pole the Cathode. The products of decomposition he called Ions. 

Lord Rayleigli found that a current of one ampere will deposit 0.017253 
grain, or 0.001118 gramme, of silver per second on one of the plates of a sil- 
ver voltameter, the liquid employed being a solution of silver nitrate con- 
taining from 15 per cent to 20 per cent of the salt. 

The weight of hydrogen similarly set free by a current of one ampere is 
.00001044 gramme per second. . 

Knowing the amount of hydrogen thus set free, and the chemical equiva- 
lents of the constituents of other substances, we can calculate what weight 
of their elements will be set free or deposited in a given time by a given 
current. 

Thus the current that liberates 1 gramme of hydrogen will liberate 7.94 
grammes of oxygen, or 107.11 grammes of silver, these numbers being the 
chemical equivalents for oxygen and silver respectively. 

To find the weight of metal deposited by a given current in a given time, 
find the weight of hydrogen liberated by the given current in the given 
time, and multiply by the chemical equivalent of the metal. 

Thus: Weight of silver deposited in 10 seconds by a current of 10 amperes 
= weight of hydrogen liberated per second X number seconds X current 
strength x 107.11 = .00001044 X 10 X 10 X 107.11 = .1118 gramme. 

Weight of copper deposited in 1 hour by a current of 10 amperes = 
.00001044 X 3600 X 10 X 31.55 = 11.86 grammes. 

Since 1 ampere per second liberates .00001044 gramme of hydrogen, 
strength of current in amperes 

_ weight in grammes of H. liberated per second 

.00001044 
_ weight of element liberated per seco nd 
~~ .00001044 x chemical equivalent of element 

Resistances of Dilute Sulphuric Acid. 

(Jamin and Bouty.) 





Ohms per c.c. at 


Ohms per 


Cu. In. 


at 


Density. 








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ELECTRO-METALLURGY. 



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ELECTRO-CHEMISTRY. 



677 



Resistances of Sulphate of Copper at 10° C. or 50° F. 

(Ewing and MacGregor.) 





Ohms per 




Ohms per 


Density. 






Density. 








c.c. 


Cu. In. 




c.c. 


Cu. In. 


1.0167 


164.4 


64.8 


1.1386 


35.0 


13.8 


1.0216 


134.8 


53.1 


1.1432 


34.1 


13.4 


1.0318 


98.7 


38.8 


1.1679 


31.7 


12.5 


1.0622 


59.0 


23.2 


1.1829 


30.6 


12.0 


1.0858 


47.3 


18.6 


1.2051 } 


29.3 


11.5 


1.1174 


38.1 


15.0 


Saturated j 



Resistances of Sulphate of Zinc at 10° C. or 50° F. 




Ohms per 




Ohms per 


Density. 






Density. 








c.c. 


Cu. In. 




c.c. 


Cu. In. 


1.0140 


182.9 


72.0 


1.2709 


28.5 


11.2 


1.0187 


140.5 


55.3 


1.2891 


28.3 


11.1 


1.0278 


111.1 


43.7 


1.2895 


28.5 


11.2 


1.0540 


63.8 


25.1 


1.2987 


28.7 


11.3 


1.0760 


50.8 


20.0 


1.3288 


29.2 


11.5 


1.1019 


42.1 


16.6 


1.3530 


31.0 


12.2 


1.1582 


33.7 


13.3 


1.4053 


32.1 


12.6 


1.1845 


32.1 


12.6 


1.4174 


33.4 


13.2 


1.2186 


30.3 


11.9 


1.4220 { 
Saturated ) 


33.7 


13.3 


1.2562 


29.2 


11.5 



Specific resistance of fused sodium chloride (common salt) at various 
temperatures. 

Temperature Cent. 720° 740° 750° 770° 780° 
Ohms per cu. cm. .348 .310 .294 .265 :247 

Application of Electro-Chemistry. 

The various forms of primary and secondary batteries may be regarded 
as applications of electro-chemistry, but they are treated as special subjects 
mother parts of this book. Other important practical applications are the 
processes for producing chemicals by electrolysis or by electrical heating. 
Among the materials thus produced in large quantities are caustic soda, 
carbonate of soda, chlorine, bleaching powder, chlorate of potash, calcium 
carbide, phosphorus, cyanide of potassium, etc. 

The production of caustic soda may be effected by electrolysing a solution 
of common salt the reaction being NaClxH 2 0=NaOHxHy.Cl the products 
being caustic soda (NaOH) which remains in solution, hydrogen and 
chlorine that pass off as gases the latter being collected and used for mak- 
ing bleaching powder. 

There is a tendency to form a mixed product of caustic soda and salt and 
a certain amount of hypochlorite of soda. These difficulties are avoided 
by separating the caustic soda from the rest of the solution either by a 
porous diaphragm or by drawing it off as fast as produced. In the Castner 
process, mercury is used as the cathode and absorbs the metallic sodium 
deposited upon it. In another chamber the sodium decomposes water and 
forms caustic soda. 



ELECTRO-CHEMISTRY. 



ELECTRO-METALLURGY. 



Calcium Carbide is produced by heating a mixture of burnt lime and 
pulverized coke or anthracite coal in an electric furnace, the reaction being: 

CaO+3C=CaC 2 +CO 

The carbonic oxide (CO) passes off as a gas and the calcium carbide after 
cooling is a solid grayish mass which is broken up for use. A rotary form 
of furnace is used at the large works of the Carbide Company at Niagara 
Falls, the material being fed in at one side and the calcium carbide being 
taken out at the other. 

ELECTRO-HETALLURGY. 

Electro-metallurgy may be denned as that branch of science which re- 
lates to the electrical reduction or treatment of metals. 

The subject may be divided into three important and quite distinct 
branches, as follows: 

1. Electrolytic Metallurgy, which consists in reducing or separat- 
ing metals by the decomposing effect which occurs when an electric current 
is passed through their compounds while in the liquid state. These com- 
pounds may be rendered liquid either by dissolving or fusing them; hence 
there are: 

(a.) Wet methods with solutions. 

(6.) Dry methods with fused materials. 

Electrolytic metallurgy is applied to the following purposes: 

(c.) Electrotyping, which is the art of reproducing the exact form of 
type, engravings, medals or other articles by electrodepositing metal on the 
article itself or on a mould obtained from it. 

(d.) Electroplating , which is the art of coating articles with an adherent 
layer of metal by electrodeposition. 

(e.) Electrolytic reduction of metals, which is the art of obtaining metals 
from their ores or compounds by electrically decomposing such ore or 
compound in the state ^f solution or fusion. 

(f.) Electrolytic refining of metals, which is the art of eliminating im- 
purities by electrodepositing the metal itself, the foreign substances being 
left in the anode or liquid, or vice versa. 

2. Electrical smelting-, which consists in reducing metallic oxides 
by carbon at a high temperature produced by the passage of an electric 
current. 

3. Electrical working- of metals, which consists in treating 
metals mechanically with the aid of heat generated by electric currents. 
Various mechanical processes which are facilitated by softening or fusing 
the metal may be effected in this way, the principal ones being: welding, 

forging, rolling, casting. 

Electrotyping.— To reproduce an engraving,typographical composition, 
or other object, a mould of gutta percha, wax, plaster or fusible alloy is 
made from the object. If it is not a conductor it is coated with graphite 
to start the action, connection being made to it by a wire or clamp put 
around it. It is used as the cathode in a bath consisting of a saturated 
solution of copper sulphate acidulated with sulphuric acid. The anode is a 
plate of copper. The ordinary thickness of deposit is .01 to .02 inch. The 
" shell" thus formed is separated from the mould and backed by afllling of 
type metal. 

Electroplating an article with an adherent coating of metal re- 
quires the article to be thoroughly cleaned mechanically and chemically. 

Cleaning-. — Solutions for cleaning Gold, Silver, Copper, Brass and Zinc 
are prepared as follows: 



For copper and brass 

Silver 

Zinc 

Iron, wrought . . . 
Iron, cast .... 



100 
100 
100 
100 
100 



Nitric 
Acid. 



Sulphu- 
ric. 



100 

10 
8 
12 



Hydro- 
chloric. 



ELECTRO-METALLURGY. 679 



Lead, Tin, Pewter, are cleaned in a solution of caustic soda. 

Objects to be plated with gold or silver must be carefully and thoroughly 
freed from acids before transfer to the solutions. Objects cleaned in soda 
or those cleaned in acid for transfer to acid coppering solutions may be 
rinsed in clean water, after which they should be transferred immediately 
to the depositing solution. 

Baths for plating-. —The reader is referred to the various books on 
electroplating for particulars, as but few, and those the most used solutions 
can be referred to here. 

Solutions should be adapted to the particular object to be plated, and 
must have little if any action upon it. Cyanide of gold and silver act chemi- 
cally upon copper to a slight extent and the objects should be connected to 
the electrical circuit before being immersed. 

Solutions are best made chemically, but can be made by passing a current 
through a plate of the required metal into the solvent. 

Copper. — A good solution for plating objects with copper is made by 
dissolving in a gallon of water 10 ounces potassium cyanide, 5 ounces copper 
carbonate, and 2 ounces potassium carbonate. 

The rate of deposit should be varied to suit the nature and form of the 
surface of the object, large smooth surfaces taking the greatest rate of 
deposit. Electrotype plates must be worked at a slow rate, owing to the 
rough and irregular surface. 

Non-metallic Surfaces may be plated by first providing a conducting sur- 
face of the best black lead or finely ground gas coke. Care is required in 
starting objects of this sort, to obtain an even distribution of the metal, and 
hollow places may be temporarily connected by the use of fine copper wire. 

Copper on iron or on any metal that is attacked by copper sulphate is 
effected by an alkaline solution. One which can be worked cold is made 
up of I ounce of copper sulphate to a pint of water. Dissolve the copper 
sulphate in a half pint of water, add ammonia until all the first formed 
precipitate re-dissolves, forming a deep blue solution, then add cyanide of 
potassium until the blue color disappears. A heavy current is required with 
this solution, enough to give off gas from the surface. This solution will 
deposit at a high rate but ordinarily leaves a rough and crystalline surface, 
and will not do good work on steel. 

A cyanide solution is the most used, takes well on steel_or brass, as well as 
on iron, and permits of many variations. 

For each gallon of water use : 

Copper carbonate 5 ozs. 

Carbonate of potash 2 ozs. 

Potassium cyanide, chem. pure 10 ozs. 

Dissolve about nine-tenths of the potassium cyanide in a portion of the 
water then add nearly all the copper carbonate, which has also been dis- 
solved in a part of the water: dissolve the carbonate of potash in water and 
add slowly to the above solution stirring slowly until thoroughly mixed. 
Test the solution with a small object, adding copper or cyanide until the 
deposit is uniform and strong. For coppering before nickel plating, the 
coating of copper must be made thick enough to stand hard buffing, and for 
this reason the coppering solution must be rich in cyanide and have just 
enough copper to give a free deposit. Use electrolytically deposited copper 
for anodes, as it gives off copper more freely. Regulate the current for the 
work in the tanks, and it should be rather weak for working this solution. 

Brass Solutions of any color may be made by adding carbonate of zinc in 
various quantities to the copper solution. The zinc should be dissolved in 
water with two parts, by weight, of potassium cyanide, and the mixture 
should then be added to the copper bath. A piece of work in the tank at 
the time will indicate the change in color of the deposit. Two parts copper 
to one zinc gives a yellow brass color. For the color of light brass add a 
little carbonate of ammonia to the brass solution. To darken the color 
add copper carbonate. Varying the amount of current will also change 
the color, a strong current depositing a greater amount of zinc, thus pro- 
ducing a lighter color. 

Silver. — The standard solution for silver plating is chloride of silver 
dissolved in potassium cyanide. This solution consists of 3 ounces silver 
chloride with 9 to 12 ounces of 98 per cent potassium cyanide per gallon of 
water. Rub the silver chloride to a thin paste with water, dissolve 9 



080 ELECTRO-CHEMISTRY. ELECTRO-METALLURGY. 



ounces potassium cyanide in a gallon of water and add the paste, stirring 
until dissolved. Add more cyanide until the solution works freely. The 
bath should be cleaned by filtering. Great care sbould be taken to keep 
the proper proportions between current, silver and cyanide. A weak cur- 
rent requires more free cyanide than a strong one, and too much cyanide 
prevents the work plating readily, and gives it a yellowish or brownish 
color. If there is not enough cyanide in the solution the resistance to the 
current is increased and the plating becomes irregular. 

The most suitable current for silver plating seems to De about one ampere 
for each sixty (60) inches of surface coated. 

O-old. — Cyanide of gold and potassium cyanide make the best solution 
for plating with gold. The solution is prepared in the same manner as the 
silver solution just described, using chloride of gold in place of chloride of 
silver. The electrical resistance of the bath U controlled by the quantity 
of cyanide, the more cyanide the less the resistance, cut an excess of 
cyanide produces a pale color. Hot baths for hot gilding require from 11 to 
20 grains of gold per quart of solution and a considerable excess of cyanide. 
Baths for cold gilding and for plating should have not less than 60 grains 
per quart and may have as much as 320 grains, this quantity being used with 
a dynamo current for quick dipping. 

Nickel. —The solution now almost universally used for nickel plating 
is made up from the double sulphate of nickel and ammonia, with the 
addition of a little boracic acid under certain conditions. 

The double salt is dissolved by boiling, using 12 to 14 ounces of the salts 
to a gallon of water, the bath is then diluted with water until a hydrometer 
shows a density of 6.5° to 7° Baume. 

Oast anodes are to be pref arred as they give up the metal to the solution 
more freely. Anodes should be long enough to reach to the bottom of the 
work and should have a surface greater than that of the objects being plated. 

Current strength should be moderate, for if excessive the work is apt to 
be rough, soft or crystalline, voltage may vary from 3.5 to 6 volts and the 
most suitable current is from .4 to .8 ampere per 15 square inches surface 
of the object. Zinc is the only metal requiring more current than this, and 
takes about double the amount named. 

A nickel bath should be slightly acid in order that the work may have a 
suitable color. An excess of alkali darkens the work and an excess of acid 
causes " peeling." 

Iron. — A hard white film of iron can be deposited from the double 
chloride of iron and ammonia, which can be prepared by the current 
process. It is somewhat used for coating copper plates to make them 
wear a long time, the covering being renewed occasionally. 

The Electro -motive JTorces suited to the different metals are : — 

Copper in sulphate, Volt, 1*5- 2'5 

" cyanide, 4* - 6" 

Silver in " 1- -2- 

Gold in " -5-3- 

Nickel in sulphate, 2-5-5-5 

The Resistance will depend on the nature of the surface. Work is 
best effected with about equal surface of anode and objects, and the coating 
will be more even, the greater the distance between them, especially where 
there are projecting points or rough surfaces. 

Copper and silver should never show any sign of hydrogen being given off 
at the objects; gold may show a few bubbles if deep color is wanted. 
Nickel is always accompanied with evolution of hydrogen, but the bath 
should not be allowed to froth. 

The Rate of Deposit is proportional to current, as described under 
the head of " Electrolysis," in the proportions given in the table of electro- 
chemical equivalents except in the case of gold, the equivalent of which in 
combination with cyanogen is 195.7, but subject to modifications dependent 
upon the hydrogen action just described; there is also a partial solution of 
the metal, so that there is always a deduction to be made from the theoret- 
ical value. Thus : — 

Gold gives about 80 to 90 per cent. 
Nickel " SO to 95 " 

Silver " 90 to 95 

Copper "98 " 



ELECTROLYTIC REFINING OP COPPER. 681 



An ampere of current maintained for one hour, which serves as a unit of 
quantity called the " ampere hour," represents 

Gramme 0376 Grain 58 

Ounce Troy 00121 ' Ounce Avoir. . . .00132 

which multiplied by the chemical equivalent will furnish the weight of any 
substance deposited. 

Separation of Metals. 

Aluminum. — There are several successful processes in use. Hall's 
process is operated on a large scale at Niagara Palls. The cell is an iron 
vessel lined with carbon, which forms the cathode, and contains molten 
cryolite (sodium and aluminum double fluoride), into which is fed the 
alumina, Al 2 0. 6 , ; this is electrolysed, the oxygen passes off as C0 2 at the 
anode, which is a carbon cylinder. The aluminum having a higher specific 
gravity than the fluoride, settles at the bottom of the bath, from which it is 
tapped or ladled off. The temperature of the bath is 1,600° to 1,800° Pahr., 
while from 7 to 8 volts are required, and a current of 5,000 amperes is used, 
producing 1 pound of metal per 10 K. W. - hours. About 1 pound of carbon 
electrode is consumed per 1 pound of aluminum produced. 

The Cowles process is chiefly for producing alloys of aluminum and sili- 
con with copper and iron. Corundum (aluminum oxide) or bauxite is mixed 
with iron tilings or granulated copper, and is smelted in a furnace as fol- 
lows : — The furnace pit is built of tire brick with holes in the ends for 
admitting the carbon electrodes ; the furnace is lined internally with limed 
charcoal, the lime keeping apart the carbon particles, which would other- 
wise connect and make a short circuit. The carbon electrodes are brought 
together and the charge of corundum, &c, is put in, the furnace is then 
covered, and the current is gradually started. The electrodes are then 
gradually separated, and the current is increased and maintained for about 
an hour, when the reduced metal is drawn from the bottom of the furnace. 
\Vith the cupro-aluminum process the current is easily maintained steady, 
but with the ferro-aluminum process the conductivity of the charge varies 
greatly during the process, and regulation of current is very difficult. 

Electrolytic Refining- of Copper. 

The most important application of electrolytic metallurgy is the refining 
of copper which is carried on at many places in this country and abroad on 
a very large scale. The crude copper obtained from the smelting furnaces 
is cast or rolled in the form of plates which are used as anodes in electro- 
lytic cells. The electrolyte is a solution of copper sulphate acidulated with 
sulphuric acid to increase its conductivity. The cathodes are usually thin 
sheets of pure copper upon which the refined copper is electrodeposited, 
the impurities are left behind in the anodes or solution, or as a scum or 
sediment. In some cases the plates are arranged in series and in others in 
parallel. The former has the advantage of requiring electrical contracts 
to be made to the first and last plates only, whereas the parallel plan re- 
quires connection to each plate; but in the series arrangement there is a 
considerable leakage of current amounting to about 15 or 20 per cent. The 
pressure required is from .2 to .4 volt per cell with a current density of 10 to 
15 amperes per square foot. It requires in practice 400 to 475 ampere-hours 
per pound of copper, the theoretical amount being 382.6 ampere-hours. 
About 8 or 9 pounds of copper are produced per kilowatt-hour at about .3 
volt which is the ordinary value. The cost of the process is about .7 cent 
per pound of copper. A great advantage of the electrolytic method of refin- 
ing copper is the fact that the silver and gold contained in the copper is left 
behind in the sediment, from which it is extracted afterward usually by 
electrolysis. The silver and gold thus recovered constitute an important 
item in the output of an electrolytic refinery. 

The Elmore process consists in depositing the copper on a revolving iron 
mandrel which forms the cathode ; an agate burnisher travels along the 
mandrel and presses the crystals of metal into a fibrous form which is said 
to account for the superior strength of the metal deposited by this process. 
The copper is removed from the mandrel by expansion, for which purpose 



682 ELECTRO-CHEMISTRY. ELECTRO-METALLURGY. 



steam is used. Specimens tested by Prof. Kennedy Lave broken at 27 to 41 
tons per square inch with an extension of 5 to 7|- per cent. Tbe tubes may 
be cut into sheetd or strips for drawing into wire. The conductivity is very 
high, being sometimes 2 or 3 per cent above Matthiessen's standard. 

Silver is refined from copper bullion by taking anodes of the bullion £ 
inch thick and 14 inches square, and cathodes of sheet silver slightly oiled". 
The electrolyte consists of water with 1 per cent of nitric acid. When tbe 
current is started the copper and silver form nitrates of copper and silver 
and free nitric acid from which the silver is deposited, leaving the copper 
in solution. Trays are placed under the cathode for catching the deposited 
silver, and if there is any copper deposited owing to the solution contain- 
ing too little silver or a superabundance of copper, the copper falls into the 
trays and is re-dissolved. 

In the Moebius process the deposit is continually removed from tbe cath- 
ode by means of a mechanical arrangement of brushes, and falls into tbe 
trays above mentioned. 



ELECTRIC HEATING, COOKING AND 
WELDING. 

HEAT riVITi AJ¥J> E^UIVALEiTi. 

The unit of heat in mechanics is the "calorie" or " lesser calorie," which 
is the heat necessary to raise one cubic centimeter of water from 4° to 5° 
Centigrade in one second. 

The British Heat Unit, known as the " British Thermal Unit," or " B.T.U.," 
is the quantity of heat necessary to raise one pound of water from 60° to 61° 
Fahrenheit, and is equal to 778 foot pounds, or 1055 Joules. The Joule is 
the heat generated by a watt in a second. 

Joule's Law shows that the heat generated in a conductor is directly 
proportional to : 

Its resistance, the square of the current strength, and the time during 
which the current flows, or, 

H= I*Rt. 

According to Ohm's law, 7 = E -f- E, hence, 

l*Rt = % IRt = Elt = ~ 
And calling Q the quantity of electricity flowing, then 

»=§<• 

and Hr=. EQ or the heat = E.M.F. x Quantity, 

in which E.M.F. is the difference of potential between the ends of the 
conductor. 

The table on the following page clearly shows the equivalent values 
of the electrical and mechanical units. 

VARIOUS IHETHODS OF UTILIZOG THE HEAT 
GENERATED BY THE ELECTRIC CURRENT. 

I. Metallic Conductors (Uninterrupted Circuit). 

1. Exposed coils of wire or strips. 

(a) Entirely surrounded by air. 

(b) Wound around insulating material. 

2. Wire or strips of metal imbedded in enamel. 

(a) In the form of coils. ) Leonard, Carpenter, Crompton, and 

(b) In flat layers. J others. 

3. Wire or strips of metal imbedded in asbestos. 

(a) In the form of coils. 

(b) In flat layers. 

4. Wire imbedded in various insulating compounds. 

(a.) Crystallized acetate of sodium, etc. Tommasi. 

5. A Film of metal. 

(a) Rare metal fired on enamel. ) T> rnrnekth ~ n ~ 

(b) Rare metal fired on mica. f Prometheus. 

(c) Silver deposited on glass. Reed. 

6. Sticks of metal. 

(a) Crystallized silicon in tubes of glass. Le Roy. 

(6) Metallic powder mixed with clay and compressed. Rarville, 

083 



684 ELECTRIC HEATING, COOKING, AND WELDING. 



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'51 



ELECTRIC COOKING. 685 



II. Heat of the Electric Arc (Interrupted Circuit). 

1. The Electric Furnace. Siemens, Cowles, Parker, and others. 

2. Heat of Arc acting upon material, producing local fusion. 

Meritens, Werdemann, Bernardos, Howells, and others. 

3. Welding by bringing metals in contact. Thomson. 

4. Deflecting Arc by Magnet. Zerener. 

III. Hydro-electrothermic System, or Water-l*ail Forg-e. 

Burton, Hoho and Lagrange. 

Referring to the above classification, Section I., the methods referred to 
under subhead 1 and 3 require no further explanation. The method under 
subhead 2 consists in imbedding the resistance wire in some fireproof insu- 
lation such as enamel or glass. This insulation is of comparatively poor 
quality as a conductor of heat, and so thin that it affords the least possible 
resistance to the flux of heat from the heated resistance. 

Tommasi (subhead 4) imbeds the coil of wire in a material having great 
latent heat of fusion, such as crystallized acetate of sodium, hyposulphide of 
sodium, etc., the principle being that the material acts as a reservoir of 
heat. The heaters, it is claimed, are first heated by immersion in hot 
water, then the current is turned on, and after they have been brought 
to the desired temperature, the current is cut off, and the heaters remain 
active for about four hours more. 

The Prometheus System (subhead 5) is extensively used in Ger- 
many, and consists of firing a broad strip of rare metal on to an enamel, 
which forms the outside of the vessel. The efficiency of this apparatus has 
been found by Prof. Dr. Kittler to be between 84 and 87 per cent. 

The Reed method of depositing a layer of silver on glass was described 
in the Electrical World, June 5, 1895. 

The method employed by JLe Roy (subhead 6) consists of inclosing 
sticks of crystallized carbon, having a specific resistance 1333 as high as that 
of ordinary arc light carbon, in glass tubes. For 110 volts rods are 100 mm. 
long, 10 mm. wide, and 3 mm. thick. This takes about 150 watts ; and 
having a surface of 26 sq. cm., the dissipation of heat is at the rate of about 

5 kg. calories per sq. cm. of surface, or an absorption of electrical energy of 

6 watts per sq. cm. of surface. 

JParville (IS Eclair age Elec, Jan. 28, 1899) uses rods of metallic 
powder, mixed with fusible clay (quartz, kaolin), compressed under a press- 
ure of 2000 kg. per sq. cm., and baked at a temperature of 1350° C. A rod 5 
cm. long, 1 cm. wide, 0.3 cm. thick, has a resistance of 100 ohms, and absorbs 
16500 watts per kg. One quart of water boils in 5 minutes with 15 amp. and 
110 volts. 

Tbe above methods are utilized in the construction of electric cooking and 
heating apparatus, while those enumerated under sections II. and III. are 
employed for purposes of welding, smelting, and forging. 

EEECTMJC COOKING. 
Cost of Operating- Electric Cooking- Utensils. 

On account of the number of variables which enter into the determination 
of the cost of electric heating and cooking, it is impossible to present any 
general data. These variables may be classified as follows : 

1. Cost of current. 2. The skill 'of the operator from the cooking stand- 
point. 3. The skill of the operator from the standpoint of using the elec- 
trical apparatus economical^. 4. The type of apparatus employed. 

It is possible, however, by assuming an arbitrary cost for ctirrent, to 
calculate the cost of heating a given quantity of Avater. Let it be required 
to heat one gallon of water at a temperature of 50° F. (10° C), without 
actuallv boiling it, to the boiling-point, or 100° C. ; it would then be elevated 
90° C. Hence 3786 cubic centimeters would be raised 90° C. or 3786 x 90= 340,- 
740 water-gramme-degrees-centigrade of heat are produced. The unit cor- 



686 ELECTRIC HEATING, COOKING, AND WELDING. 

responding to a water-gramme-degree-centigrade is the calorie, which 
requires an expenditure of 4.18 joules, so that the work required to be done 
in raising a gallon of water to the temperature of 100° C. is equal to 340,- 
740 x 4.18 = 1,424,293 joules. Assuming the cost of electric current, in large 
quantities, to be 5 cts. per kilowatt-hour (which is equal to 3,600,000 joules, 
as 1 joule = 1 watt per second), the cost of raising one gallon of water to 
the boiling-point is approximately 2 cents. If we assume the current to cost 
15 cts. per kilowatt-hour, then the cost would be 6 cents. 

This calculation, however, is strictly theoretical, as the assumption is 
made that all the heat generated is utilized in raising the temperature of 
the water. This, of course, is not the case, as a certain amount of the heat is 
transmitted to the metal vessel and the air during the time of the opera- 
tion (about 15 minutes). Assuming the efficiency of the vessel to be 70 per 
cent, which represents the ratio between the useful and the total developed 
heat, then the actual cost of heating a gallon of water from 10° to 100° C. at 
a cost for current of 5 cts. per kilowatt-hour would be 2 x -V°<? = 2.86 cents, 
or at 15 cents per kilowatt-hour would be 3 X 2.86 = 8.58 cents. 

Before proceeding to cite actual results achieved with electric cooking 
apparatus, the following table, furnished by the American Electric Heating 
Corporation, may be of value : 

Time Required. 

Stoves and griddles are ready for use, i.e., have reached a temperature for 
cooking, in from 5 to 8 minutes from time current is turned on. Broiler, 12 
to 14 minutes ; Oven, 20 minutes ; Farina Boilers, 6 to 8 minutes ; Chafing- 
dishes, 10 minutes ; Stew-pan, 5 minutes ; Laundry-irons, 8 to 10 minutes 
very hot ; Tailor's Irons, 6 to 12 minutes ; Foot-warmers, 5 to 15 minutes ; 
Curling-iron Heater, 6 to 8 minutes ; Plate-warmer, 10 minutes ; Soldering- 
iron, 5 to 8 minutes ; Glue-pots, 15 to 30 minutes. 

To boil water, starting with water and heater cold, Stew-pan, 1 pint 16 
minutes ; small Teakettle, 1 pint 15 minutes ; Five O'clock, 1 quart 18 
minutes ; 6 inch stoves (using suitable flat-bottom vessel), 1 quart 18 min- 
utes ; Teakettle, 1 quart 15 minutes, 2 quarts 28 minutes ; Hot-water Urns, 
1 gallon, one-half full in 35 minutes, full in one hour ; 2 gallons, one-half 
full in 50 minutes, full in 1 hour 20 minutes ; three gallons, one-half full in 
37 minutes, full in 60 minutes ; 5 gallons, one-half full in 30 minutes, full in 
55 minutes. Very hot water, about 175 degrees F., can be had in about two- 
thirds the time stated for boiling. Water-heaters can be made to boil the 
quantities mentioned in about half the time, but the current required 
would be nearly double that mentioned for any standard articles. Coil- 
heaters when immersed in a covered vessel give the following results, using 
maximum current, and after water boils will maintain it at the boiling- 
point with one-fourth of the maximum. 

(400 Watts) 1 pt., 10 minutes ; 1 qt., 19 minutes ; 2 qts., 35 minutes. 
(660 " ) 1 pt., 7 minutes; 1 qt., 12 minutes ; 2 qts., 21 minutes; 

3 qts., 28 minutes. 
(880 " ) 1 pt., 5 minutes; 1 qt., 8 minutes; 2 qts., 15 minutes ; 1 

gal., 28 minutes. 
(1100 " ) 1 qt., 6 minutes ; 1 gal., 18 minutes ; 2 gals., 35 minutes ; 

3 gals., 45 minutes. 
(1650 " ) 2 qts., 8 minutes ; 1 gal., 14 minutes ; 2 gals., 26 minutes ; 

3 gals., 35 minutes. 

Practically the same results are obtained with immersion disk-heaters of 
the same watt capacity. 

Mr. Colin (Bui. Soc. Int. ties Elec, Feb., 1897) found that the surface tem- 
perature of a broiler should be from 270° to 280° C. The total heat emitted 
will then be 11922 calories per hour. The surface of such a broiler 20 cm. by 
14 cm., will require 140 watts per sq. decimeter for ordinary heating ; 120 
watts will give the best results. 

C. O. Grimshaw (Lond. Elec, Dec. 23, 1898) estimates the cost of electric 
cooking, based on 8 cts. per kilowatt-hour, as follows : — 



ELECTRIC COOKING. 



687 



Apparatus. 


Capacity. 


Cost per Hour 
in Cents. 


Cost for One 
Operation from 
Cold in Cents. 


Kettle 

Griller 

Saucepan .... 
Fish kettle . . . 


1J pints 
2 chops 
2 quarts 
16 quarts 


2.56 
4.48 
3.2 
9.12 


0.96 
1.06 
1.6 



At the Carmelite Hospice, Victoria Free Park, Niagara, an electric range 
has a heating surface of 6 sq. ft., each square foot consuming 15 amp. at 110 
volts. The two small ovens consume 23 amp. each, the large one 50 amp. 
The oven equipment is designed for four 25 lb. roasts at one time. In the 
small ovens bread is baked in 18 minutes. The current for water heating, 
cooking, and lights costs $25 per H. P., while the 75 H. P. used in heating 
the corridor and bedrooms is secured at about one-fifth this price per H. P. 

Mr. Dowsing, in the London Electrical Review, refers to a trial with a gas 
oven in which it was found that out of a total of over 13,000 heat units 
required in roasting a joint of 8.5 lbs. 2,203 units were actually used in the 
food itself, or about 16 per cent. 

In a lecture before the A. I. E. E. in 1897, Prof. J. P. Jackson made the 
following statement : 

To determine the relative cost of cooking with electricity and coal, the 
same foods were cooked on the No. 8 Othello coal stove ordinarily used by 
the family. The coal was carefully weighed. The results gave an average 
of 12.6 pounds per meal, which at $ 5.00 per ton gives a cost of 3.15 cents per 
meal. The results show the cost of cooking by coal to be about 19 per cent 
of the cost of cooking by electricity. 

Prof . Dr. Kittler made a series of tests of the " Prometheus " cooking 
apparatus, and from a table prepared by him the following data are taken: 



Quantity of 
Water Heated. 


Time 
required, 
Seconds. 


Energy con- 
sumed, 
Watt Seconds. 


Temp. 
Incr. 

Fahr. 


Efficiency 

of 
Apparatus. 


300 grams . . . 
400 grams . . . 


255 
327 


131,835 
169,400 


191.3 
191.3 


83.9% 
87.1% 



Mr. R. E. Crompton accurately measured the temperature of a number of 
electric heating utensils, and utilized the facts obtained in the compilation 
of the following table : 



Time 
in 

Minutes. 



Energy 
K.W. hrs. 



Cost at 
8 cts. per 
K.W. hr. 



Temp. 
Fahr. 

Scale. 



Table I. — Showing en- 
ergy required to raise a 
heater plate from 50° F. 
to 400° F. in half an 
hour. 



0.116 
0.164 
0.248 
0.404 



1.34 
2.00 
3.22 



50 
257 
332 
337 
400 



688 



ELECTRIC HEATING, COOKING, AND WELDING. 





Time 

in 

Minutes. 


Energy 

in 

K.W. hrs. 


Cost at 
8 cts. per 
K.W. hrs. 


Temp. 
Fahr. 
Scale. 


Table II. — Shows the 
energy required for a 
radiator plate such as 
is used for heating the 
air of a room. 


10 
30 
40 
50 
60 


'o.09l' 
0.277 
0.350 
0.430 
0.500 


0.728' 

2.2 

2.8 

3.44 

4.00 


50 
171 
240 
257 
261 
264 


Table III. — Shows the 

energy required to hoil 
1 lb. of water in a kettle. 


18 


0.075' 


0.64 ' 


50 

212 


Table IV. — Shows en- 
ergy required by a 
smaller kettle contain- 
ing | lb. of water, i.e., 
sufficient for two cups 
of tea. 


12 


'0.651' 


0.4 


50 

212 



This shows that the efficiency of the operation in Table III. is 63 per- 
cent, and that in Table IV. is 71.5 per cent. 

The following curves show the rise of temperature in the case of a heater 
plate and a radiator and also the energy consumed: 

400 















¥ 




10^, 




«•■ 




^•i"*" 


f 


J> 




*&&■■ 




" 




>P" 











20 30 40 

TIME IN MINUTES 
Fig. 1. 



Efficiency of Heating- Apparatus. 

In the foregoing references it will be seen tbat the efficiency of electric 
cooking apparatus varies from about 63 per cent to 90 per cent (for ovens), 
depending upon a number of variable conditions, such as time, size, quantity 
to be heated, temperature rise, etc. 

According to Mr. Crompton, the efficiency of an ordinary cooking-stove 
using solid fuel is only about 2 per cent, 12 per cent being wasted in obtain- 



ELECTRIC CAR HEATING. 689 



ing a glowing fire, 70 per cent going up the chimney, and 16 per cent being 
radiated into the room. 

In a gas-stove, considering that the number of heat units obtainable from 
the gas at a certain price is but small compared with solid fuel, the venti- 
lating current required for the operation alone consumes at least 80 per 
cent of the heat units obtained by burning the gas. 

In the case of an electrical oven, more than 90 per cent of the heat energy 
can be utilized ; and thus, although possibly 5 to 6 per cent only of the heat 
energy of the fuel is present in ths electrical energy, 90 per cent of this, or 
4£ per cent of the whole energy, actually goes into the food, and thus the 
electrical oven is practically twice as economical as any other oven, whether 
heated by solid fuel or by gas. 

ELECTRIC ItJUDIATOMS. 

Unless electricity is produced at a very low cost it is not commercially 
practicable to heat residences or large buildings. While this is true, the 
electric heater still has a field of application, in heating small offices, 
bathrooms, snuggeries, cold corners of rooms, street railway waiting 
rooms, the summer villa on cool evenings, and in mild climates a still 
wider range. It has the peculiar advantage of being instantly available, 
and the amount of heat is regulated at will. The heaters are perfectly 
clean, do not vitiate the atmosphere, and are portable. 

According to Houston and Kennelly, one joule of work expended in 
producing heat will raise the temperature of a cubic foot of air about 
i o jr_ 

The amount of power required for electrically heating a room depends 
greatly upon the amount of glass surface in the room, as well as upon 
the draughts and admission of cold air. 

In order to make a comparison between heating an ordinary city house 
by means of coal burnt in a furnace and by electricity furnished by a cen- 
tral station, let it be assumed that 100 lbs. of coal are' consumed per day in 
the furnace. Assuming the furnace to have an efficiency of 50 per cent, 
50 lbs. of coal are utilized throughout the building in the form of heat. 
Reducing this to actual horse-power we have 

50 X 14,000 , j . ., 
700,000 heat » nits - 

700,000 X 778 = 544,600,000 ft.-lbs. 

544,600,000 



33,000 
16,503 



= 16,503 H.-P. minutes. 



275 H.-P. hours. 



Assuming that a H.-P. hour is furnished at 5 cents the cost would be 
275 X .05 = $13.75. 

ELECTRIC CAR IIEATI\ft 

At the Montreal meeting of the American Street Railway Association in 
1895, Mr. J. F. McElroy read an exhaustive paper on the subject of car- 
heating, from which the following abstracts are taken : 

In practice it is found that 20,000 B. T. U. are necessary to heat an 18 to 
20 foot car in zero weather. When the outside temperature is 12^ ° F. 
only 16,000 B. T. U. are required, etc., which shows the necessity of hav- 
ing electric heaters adjustable. 

The amount of heat necessary in a car to maintain a given inside tem- 
perature, depends on : 1. The amount of artificial heat which is given to it. 
2. The number of passengers carried. The average person is capable of 
giving out an amount of heat in 24 hours which is equal to 191 B. T. U. 



690 ELECTRIC HEATING^ COOKING, A^fD WELDING. 




Fig. 2. 



Cost of Car Heatiiu 



The following table was compiled by Mr. McElroy from the reply re- 
ceived from the Albany Railway Company : 
Average fuel cost on Albany Railway, per amp. hour = .241 cent. 
Average total cost for fuel, labor, "oils, waste, and packings per amp. 
hour = .423 cent. 





Cost of fuel per hour for heating a car 

with electric heaters with coal at 

$2.00 per 2000 lbs. 




Position of Switch. 




1st 


2d. 


3d. 


4th. 


5th. 




Amperes equal. 




2.14 


2.88 


6.88 


8.09 


12.0 


Simple high speed condensing . . 
Simple low speed condensing . . 
Compound high speed condensing 
Compound low speed condensing 


cts. 

.43 
.40 
.39 
.36 


cts. 

.58 
.54 
.52 
.48 


cts. 

1.40 
1.30 
1.27 
1.17 


cts. 

1.62 
1.51 
1.47 
1.36 


cts. 

2.41 
2.24 
2/20 
2.03 



Average Cost Per Day for Stoves. 

33 lbs. of coal at $4.55 per ton $.075 

Repairs 005 

Dumping and removing coal and ashes, coaling up 
and kindling fire, including cost of kindling, 

and part of cleaning car 100 

Removing stoves for summer, installing for win- 
ter, repairing head linings, repainting, etc., 

average per day 0125 

Total $.1925 



ELECTRIC WELDING. 



691 



ELECTRIC IRONS FOR DOMEiTIC AND INDUS- 
TRIAL PVRPOi£§. 

Comparing the hand-irons heated by gas with those heated electrically, it 
is claimed that if gas can be purchased at $1.25 per 1000 cu. ft., and the 
cost of electricity is about 1 cent per H P., the two systems are about on a 
par, as far as cost only is concerned. 

According to the American Electric Heating Corporation, the power con- 
sumption for the various types of irons is as follows : — 

Watts 

4 lbs. Troy Polishing, diamond face 330 

3k lbs. Small Seaming (can be connected to lamp socket) . . . 200 

4lbs. Gentleman's Small Hat Iron 200 

5J lbs. Light Domestic 500 

5£ lbs. Light Domestic, round nose 500 

7 lbs. Domestic 600 

9 lbs. Heavy Laundry 680 

9 lbs. Hatters' 550 

9 lbs. Corset 500 

15 lbs. Hatters' Factory 550 

5£ lbs. Morocco Bottom 500 

Morocco Bottom, round nose 500 



ELECTRIC lVi:iJ>l\<; A .\ l» S OIM. I \ <- 

The current employed in electric welding may be either continuous or 
alternating. By the use of alternating currents, a slightly more uniform 
heating of the contact surfaces is obtained, because alternating currents 
tend to develop a greater heat at the surface of a large mass than at the 
central portions. 

Thomson Electric Welding* Process. 

The principle involved in the system of electric welding, invented by 
Prof. Elihu Thomson, is that of causing currents of electricity to pass 
through the abutting ends of the pieces of metal which are to be welded, 
thereby generating heat at the point of contact, which also becomes the 
point of greatest resistance, while at the same time mechanical pressure is 
applied to force the parts together. As the current heats the metal at the 
junction to the welding temperature, the pressure follows up the softening 
surface until a complete union or weld is effected ; and, as the heat is first 
developed in the interior of the parts to be welded, the interior of the joint 
is as efficiently united as the visible exterior. 

Horse-Power Used in Electric Welding-. 

The power required for the different sizes varies nearly as the cross sec- 
tional area of the material at the joint where the weld is to be made. 

Within certain limits, the greater the power, the shorter the time ; and 
vice versa. 

The following tables are based upon actual experience in various works, 
and from very careful electrical and mechanical tests made by reliable 
experts. The time given is that required for the application of the current 
only. 

Round Iron or Steel. 



Diameter. 


Area. 


H.-P. Applied 
to Dynamo. 


Time in 
Seconds. 


£in. 


.05 


2.0 


10 


£ in. 
h in- 


.10 


4.2 


15 


.22 


6.5 


20 


f in. 


.30 


9.0 


25 


| in. 


.45 


13.3 


30 



692 ELECTRIC HEATING, COOKING, AND WELDING. 
Extra, Heavy Iron JPipe. 



Inside 


Area. 


H.-P. applied 


Time in 


Diameter. 


to Dynamo. 


Seconds. 


i in. 


.30 


8.9 


33 


I in. 


.40 


10.5 


40 


1 in. 


.60 


16.4 


47 


li in. 


.79 


22.0 


53 


H in. 


1.10 


32.3 


70 


2 in. 


1.65 


42.0 


84 


2h in. 


2.25 


63.7 


93 


3 in. 


3.00 


96.2 


106 



General Table. 



Iron and Steel. 


Copper. 


Area in 


Time in 


H.-P. applied 


Area in 


Time in 


H.-P. applied 


sq. in. 


Seconds. 


to Dynamos. 


sq. m. 


Seconds. 


Dynamos. 


0.5 


33 


14.4 


.125 


8 


10.0 


1.0 


45 


28.0 


.25 


11 


23.4 


1.5 


55 


39.4 


.375 


13 


31.8 


2.0 


65 


48.6 


.5 


16 


42.0 


2.5 


70 


57.0 


.625 


18 


51.9 


3.0 


78 


65.4 


.75 


21 


61.2 


3.5 


85 


73.7 


.875 


22 


72.9 


4.0 


90 


83.8 


1.0 


23 


82.1 



Axle Welding-. 

\" round axle requires 25 Horse-power for 
1" square " " 30 " 

\\" round " " 35 " 

\\" square " " 40 " 

2" round " " 75 " 



2" square " 



90 



45 seconds. 
48 " 
60 
70 
95 
100 



The slightly increased time and power required for welding the square 
axle is not only due to the extra metal in it, but in part to the care which it 
is best to use to secure a perfect alignment. 



1" 

¥ 

2" 



Tire Welding-. 

x A tire requires 11 Horse-power for 15 seconds. 

x I" " " 23 " " " 25 

xf" " " 23 " " " 30 

x i// « u 23 " " " 40 

X i// u «« 29 « « .. r, 5 

x a// u u 42 „ u « G2 



The time above given for welding is of course that required for the actual 
application of the current only, and does not include that consumed by 
placing the axles or tires in tlie machine, the removal of the upset, and 
other finishing processes. 

From the data thus submitted, the cost of av elding can be readily figured 
for any locality where the price of fuel and cost of labor are known. 



HYDRO-ELECTROTHERMlC SYSTEMS. 693 



HYDRO-EIECTROTHERMIC SYSTEMS. 
13 olio and Eagrange System. 

In this system an electrolytic bath is employed, into which an electric 
current of considerable E.M.F. is led, passing from the positive pole which 
forms the boundaries of the bath and presents a large surface to the elec- 
trolyte and thence to the negative pole, consisting of the metal or other 
material to be treated, and Avhich is of relatively small dimensions. 

Through the electrolytic action hydrogen is rapidly evolved at the nega- 
tive pole and forms a gaseous envelope around the pole ; as the gas is 
a very poor conductor of electricity, a large resistance is . thus introduced 
in the circuit, entirely surrounding the object to be treated. The current in 
passing through this resistance develops thermal energy, and this is com- 
municated to the metal or other object which forms the negative pole. 

This system has been extensively used in England, and is described in 
The Electrical World, Dec. 7, 1895. 

Burton Electric Forge. 

In a patent granted to George D. Burton on an electrolytic forge, the 
portion to be heated is placed in a bath consisting of a solution of sal soda, 
or water, carbonate of soda, and borax. The tank is preferably made of 
porcelain or fire-clay. The anode plate has a contact surface with the 
liquid much greater than the area of contact of the article to be heated. 
This plate is composed of lead, copper, carbon, or other suitable conducting 
material. 

Zerener System. 

In this system an arc is used in combination with a magnet which deflects 
the arc, making a flame similar to that of a blow-pipe, but having the tem- 
perature of the arc. The apparatus contains a self-regulating device 
which is driven by a small electric motor ; for welding iron a current of 40 to 
50 amperes at 40 volts Avill suffice for strips of metal three mm. thick. 

Bernardoi System. 

In this system the article to be operated upon is made to constitute one 
pole of the electric circuit, while a carbon pencil attached to a portable 
insulated holder, and held by the workman, constitutes the other pole, the 
electric arc — which is the heating agent of the process — being struck 
between the two poles thus formed. This system has been used extensively 
in England for the repair of machinery. The Barrbeat-Strange Patent 
Barrel Syndicate use this system for the welding of the seams of sheet- 
steel barrels. 

Voltex Process for "Welding- and Brazing 

Consists in the use of an electric arc formed between two special carbon 
rods inclined to each other at an angle of about 90°. The whole apparatus 
can generally be held in one hand. With gas and coke, gas costing only 
70 cents per 1000 cubic feet, it is claimed the complete cost of brazing and 
filling up a bicycle frame is .$1.43, while with the Voltex process, at 6 cents 
per kilowatt hour, it is only 46 cents. 

Stassano Process of Electric Smelting* 

Consists of heating, in an arc furnace, briquettes composed of iron ore, 
carbon, and lime made into a paste with tar. The smelting process occurs 
in a blast furnace, the iron being reduced, and the siliceous matter of the 
ore slagged off. 

Annealing- of Armor Plate. 

The spot to be treated is brought to a temperature of about 1000 ° F. 
The current used is equivalent to 40,000 amperes per square inch, a density 
which is only possible by the use of cooling by water circulation. The 
operation generally takes seven minutes. 



694 ELECTRIC HEATING, COOKING, AND WELDING. 



Electric Hail Welding-. 

The " Electric " joint, applied by the Lorain Steel Co., is made by Avelding 
plates on both sides of the web of the rail. The plates shown in Fig. 4 
are 1 inch by 3 inches, by 18 inches, and have three bosses, three welds 



OlAGRANi OF CONNECTIONS OF RAIL WELDER 



T • TROLLEY 
CM-CIRCUIT BREAKER 

R.R-RHEOSTATS 
M - UOTQR 
B - BOOSTER 




» T' ROTARY TRANSFORMER 

W.T MELOING TRANSFORMER 

a.W'SWITGH 



<£T 



& 



RC' REACTIVE COIL 
n.C-WElDING CLAMP 



SKETCH OFB A IK USED IN WELDING 




o 




o 


• 
■ 

i 

• 

T 


1 


8' 




[ 


i 


( _^ 


£_ 


K r— *- 






1 -^ 



Web Plates 

Figs. 3 AND 4. — The Lorain Steel Company Method of Electric Welding. 

being made at each joint. Great pressure up to 35 tons is maintained on 
the joint whilst making and cooling. The welding current runs as high as 
25,000 amperes. The connections are shown in Fig. 3. 

IUSB DATA. 

In a lecture on " The Rating and Behavior of Fuse Wires," before the 
A. I. E. E., in October, 1895, Messrs. Stine, Gaytes, and Freeman arrived at 
the following conclusions : 

1. Covered fuses are more sensitive than open ones. 

2. Fuse wire should be rated for its carrying capacity for the ordi- 

nary lengths employed. 
2 (a). When fusing a circuit, the distance between the terminals 
should be considered. 



FUSE DATA. 695 



On important circuits, fuses should be frequently renewed. 

The inertia of a fuse for high currents must be considered when 
protecting special devices. 

Fuses should be operated under normal conditions to ensure cer- 
tainty of results. 

Fuses up to five amperes should be at least 1J inch long, one- 
half inch to be added for each increment of five amperes 
capacity. 

Round fuse wire should not be employed in excess of 30 amperes 
capacity. For higher currents flat ribbons exceeding four 
inches in length should be employed. 

(For additional data on Fuses see p. 204.) 



SOME NOTES ON THE 
OPERATION OP ELECTRIC MINING PLANTS. 

From Pamphlet by General Electric Company. 

Mr. F. J. Piatt of the Scranton Electric Construction Company, Scranton, 
Pa., gives some figures on electric haulage. They are from plants which 
have been in operation for one year or longer. The expenses given are the 
actual figures for labor, oil, repairs, etc. 

In figuring the cost of mule-power, the cost per mule has been taken at 
50 cents per working-day, which includes feed, attendance, medicine, shoe- 
ing, harness, and the item of mortality. Depreciation on the electric plant 
is figured at 5%, and is given per working-day. 

The first plant on whic'b Mr. Piatt presents figures is the Green Ridge 
Colliery, installed in March, 1895, for Mr.' O. S. Johnson, in the city of 
Scranton. 

The Cireen ltitlg-e Colliery. 

The Green Ridge Colliery plant consists of one 100 H.P. automatic, high- 
speed engine, and one 75 H.P. dynamo, with switchboard and station 
equipment, all of which are installed in a frame building 30 feet by 45 feet. 

From the dynamo a feeder wire is run down the slope 1,000 feet to the 
main gangway, where a 6^ ton electric locomotive is in operation over about 
1J miles of trolley road. This locomotive gathers trips from three different 
points in the mines, and delivers them to the foot of the outside slope. 
The main gangway, which is very crooked, is about 3,100 feet long, and 
branching from it are two other roads, one of which is 1,000 feet and the 
other 2,100 feet in length. For the past year this locomotive has made a 
daily average of twenty trips, each trip consisting of eight cars, which is 
very much below its capacity. 

The grades on the main roads are about 1% in favor of the loaded and 
against the empty cars. On the 1,000 foot branch the locomotive has about 
500 feet of 3% and 500 feet of 1% grade against the empty cars. On the 2,100 
foot branch the grades are very uneven, and most of them are against the 
loaded cars. The grades of this road, against the loaded cars, consist ap- 
proximately of 150 feet of 1% grade, 500 feet of 2% grade, 350 feet of 5J% 
grade, and 450 feet of 3£% grade. 

This 6£ ton locomotive has been hauling trips of four cars up these grades 
ever since it was installed, and on some days has hauled trips of five cars. 

The roof of the mine is very low, being about five feet in the highest 
places ; and as this height was obtained by blowing the roof over the center 
of the road, the height on the main road will not average much over four 
feet. This is one difficulty which would have been met had a steam loco- 
motive been introduced instead of an electric locomotive. 

Cost of Haulag-e at tlie Green Ridg-e Colliery. 

After very carefully going over all the expenses connected with this 
plant, the following results were obtained : 

The plant cost $7,625.18. Depreciation at 5% per year would amount to 
$381.25, or taking 200 working-days per year the depreciation per working- 
day would be $1.90. 

Cost of operation per day is as follows : 

Station Engineer $1.75 

Motorman 1.75 

Helper 1.60 

Repairs 76 

Depreciation 1.90 

Oil and waste 20 

Total $7.96 



OPERATION OF ELECTRIC MINING PLANTS. 697 



The coal hauled per day hy the electric locomotive is 2S8 tons, at a cost 
per ton, as shown above, of 2.76 cents. 

To haul this coal by mule-power would require 

Seventeen mules at 50 cents each $8.50 

Three drivers at $1.45 each 4.35 

Three drivers at $1.25 each 3.75 

Four boys at $1.00 each 4.00 

Total $20.60 

This shows a cost for haulage by mule-power of 7.15 cents per ton, and a 
saving by electric haulage of 4.39 cents per ton. On the 288 tons hauled per 
day the saving is $12.64, and for a year of 200 working-days it amounts to 
$2,528.00. 

This locomotive has averaged 30 miles per day, making a total of about 
12,700 miles since it was installed. 

The expense of repairs taken on the basis of mileage is a trifle over two 
cents per mile. 

This statement shows the actual results at this particular plant, and 
what is being saved per day. The number of mules saved in the above case, 
is the number that it would require to haul an amount equal to the output 
of the locomotive on any one day ; but it is doubtful if seventeen mules 
would be able to do this work continually, as they would interfere with 
each other on the main roads, and would not deliver the coal as regularly as 
does the locomotive. 

Among others referred to are the two electric haulage plants at the mines 
of the New York and Scranton Coal Company, at Peckvilie, Pa. The 
figures given are based on the expenses- of the year 1896. 

The ]¥ew York and Scranton Coal Company. 

One of the mines operated by the New York and Scranton Coal Company 
is knoAvn as The Sturges Shaft. The plant consists of a 160 H.P. engine and 
generator and a 6£ ton locomotive, operating over 4,500 feet of trolley road. 
The cost of the plant was $6,103.00. The depreciation per year at 5% would 
amount to $305.15, or for 200»wor king-days, $1,52 per day. 

Cost of operation per day is as follows : 

Motorman $1.75 

Helper 1.25 

Electrician .78 

Repairs 1.03 

Depreciation 1.52 

Oil 24 

Total $6.57 



The coal hauled per day is 250 tons, at a cost per ton, as shown above, of 
2.62 cents. 
To haul this coal by mule-power would require 

Fourteen mules at 50 cents each $7.00 

Seven boys at $1.35 each 9.45 

Total $16.45 

This shows a cost for haulage by mule-power of 6.58 cents per ton, and a 
saving by electric haulage of 3.96 cents per ton. On the 250 tons hauled per 
day the saving is $9.90, and for a year of 200 working-days it amounts to 
$1,980.00. 



698 ELECTRICITY IN MINES. 



The locomotive runs about 32 miles per day, and up to this time has 
covered about 7,800 miles, with a cost for repairs of 2.7 cents per mile. 

The other haulage plant operated by the New York and Scranton Coal 
Company is located at the tunnel opening. 

The cost of the plant was $7,039.00. The depreciation per year at 5% 
would amount to $351.95, or for 200 working-days $1.75 per day. 

Cost of operation per day is as follows : 

Motorman $1.75 

Helper 1.25 

Electrician .78 

Repairs .65 

Depreciation 1.75 

Oil 24 

Total $6.42* 

The coal hauled per day is 600 tons, at a cost per ton as shown above, of 
1.07 cents. 

To haul this coal by mule-power would require 

Twelve mules at 50 cents each . $6.00 

Six boys at $1.35 each 8.10 

Total $14.10 

This shows a cost for haulage by mule-power of 2.35 cents, and a saving by 
electric haulage of 1.28 cents per ton. On the 600 tons hauled per day the 
saving is $7.68, and for a year of 200 working-days it amounts to $1,536.00. 

Tlie Hillside Coal and. Iron Company. 

The Hillside Coal and Iron Company was one of the first companies to 
install electric haulage. At Forest City, Fa., they have two openings 
operated by electric haulage from one power-house. The power-house con- 
tains about 150 Kw. direct connected generators and one 62 Kw. belt driven 
machine. At what is known as the " No. 2 Shaft" they have one twenty- 
ton, eight-wheel locomotive, one twelve-ton single motor locomotive, and 
one six-ton locomotive. At the Forest City Slope there is a twelve-ton 
single motor locomotive. In addition to this, they have two electric pumps. 

The plant here has been in operation since 1891, although the power-house 
has been increased and rebuilt since the original plant was installed. 

Mr. W. A. May, Superintendent, very kindly furnished the folloAving 
figures, which are on exactly the same basis as the figures in Mr. Flatt's 
paper. 

Cost of operation per clay is as follows : 

No. 2 Shaft. Forest City Slope. 

Engineer of power-house . . . $1.20 $0.60 

Motormen 4.23 2.11 

Helpers (Brakemen) 3.20 1.60 

Electrician 1.67 .83 

Repairs to motors 5.95 4.09 

Depreciation, 5% 5.20 2.60 

Oil and waste .22 .14 

Total $21.67 $11.97 

Coal hauled per day — tons . . 989 541 

Cost per ton $.0219 $.0221 

This plant has never been operated with mules, but the mine foreman has 
gone over the matter very carefully, and has made up the following estimate 
of the number of mules it would require to do the work. He finds that it 
would take fifty-three mules in the shaft and twenty-four in the slope. 
Again using Mr. Piatt's figures, we get the following cost per day for haul- 
age by mule-power in No. 2 Shaft. 



OPERATION OF ELECTRIC MINING PLANTS. 699 

Fifty-three mules at 50 cents each $26.50 

Twenty-four drivers at $1.48 each 35.52 

Twenty-four team leaders at $1.04 each .... 24.96 

Total $86.98 

This shows a cost for haulage by mule-power of 8.79 cents per ton and a 
saving by electric haulage of 6.60 cents per ton. On the 989 tons hauled per 
day the saving is $65.27, and for a year of 200 working-days it amounts to 
$13,054.00. 

In the Forest City Slope the cost per day for haulage by mule-power is as 
follows : 

Twenty-four mules at 50 cents each $12.00 

Ten drivers at $1.48 each 14.80 

Ten team leaders at $1.04 each 10.40 

Two runners at $1.59 each 3.18 

Total $40.38 

This shows a cost for haulage by mule-power of 7.47 cents per ton, and a 
saving by electric haulage of 5.26 cents per ton. On the 541 tons hauled per 
day the saving is $28.46, and for a year of 200 working-days it amounts to 
$5.*692.00. 

Mr. May remarks that in their particular case this estimate is not entirely 
correct, as the expenses of the engineer, motormen, helpers, etc., are steady 
expenses, their time on idle days being occupied with more or less running 
around and making repairs about the mines. They have therefore made an 
additional set of figures, using the actual number of days that the mines 
were running, with the actual cost. The No. 2 Shaft ran 141J days, and the 
Forest City Slope 138J days. Under these circumstances the cost of oper- 
ation per day is as follows : 



Engineer of power-house . 

Motormen 

Helpers (Brakemen) . . . 

Electrician 

Repairs to motors .... 

Repairs to line 

Repairs to generators . . 

Fireman 

Depreciation, 5% .... 
Oil and waste for motors . 
Oil and waste for generators 
Interest on plant at 3% 

Total 

Coal hauled per day — tons 
Cost per ton 

Then, again, taking their own figures on the cost of keeping what mules 
they have, they obtained the following cost per working-day for haulage in 
No. 2 Shaft : 

The depreciation on 53 mules, at $1.67 each per month, is $88.51, and for 12 
working-days per month the depreciation per day is $7.38. 

Depreciation on 53 mules $7.38 

Feed for 53 mules (at 25 cents each per day per month) 33.12 

Shoeing and harness 1.59 

Care of mules 3.97 

Forty-eight drivers and team-leaders 60.48 

Total , , , = . .,,'..... $106.54 



No. 2 Shaft. 


Forest Citj 


$2.84 


$1.45 


9.31 


4.76 


3.61 


2.63 


3.68 


1.87 


8.42 


5.89 


.46 


.03 


.61 


.30 


2.50 


1.26 


8.17 


4.16 


.35 


.21 


.74 


.37 


4.41 


2.25 


$45.10 


$25.18 


989 


541 


$.0456 


$.0465 



JOO ELECTRICITY IN MINES. 



This shows a cost for haulage by mule-power of 10.77 cents per ton, and a 
saving by electric haulage of 6.21 cents per ton. On the 989 tons hauled per 
day the saving is $61.42, and for a year of 141J days it amounts to $8,675.75. 

In the Forest City Slope the depreciation figured as above on 24 mules is 
$3.34, and the detailed cost of haulage by mule-power is as follows : 

Depreciation on 24 mules $3.34 

Feed for 24 mules (at 25 cents each per day per month) 15.00 

Shoeing and harness .72 

Care of mules 1.80 

Twenty-two drivers, leaders, and runners . . . 28.38 

Total $49.24 

This shows a cost for haulage of mule-power of 9.10 cents per ton, and a 
saving by electric haulage of 4.45 cents per ton. On the 541 tons hauled per 
day the saving is $24.07, and for a year of 138| days it amounts to $3,339.71. 

To the cost of the mule-power might yet be added interest at 3% on the 
value of the mules and harness, but as it has not heretofore been included, 
it has been left out here. 

From the foregoing it will be seen that in either case there is a consider- 
able saving in favor of electric haulage, and that this saving will increase 
as the number of idle days increases and with the increase in tonnage in the 
colliery. 



LIGHTNING CONDUCTORS. 

Views concerning the proper function and value of lightning rods, con- 
ductors, arresters and all protective devices have undergone considerable 
modification during the past ten years. There may he said to be four 
periods in the history of the development of the lightning protector. The 
first embraces the discovery of the identity of lightning with the disruptive 
discharge of electrical machines and Franklin's clear conception of the 
dual function of the rod as a conductor and the point as a discharger. The 
second begins with the experimental researches of Faraday and the minia- 
ture house some twelve feet high, which he built and lived in while testing 
the effects of external discharges. Maxwell's suggestion to the British 
Association, in 1876, embodies a plan based upon Faraday's experiments, for 
protecting a building from the effects of lightning by surrounding it with a 
cage of rods or stout wires. The third period begins with the experiments 
of Hertz upon the propagation of electro-magnetic waves, and finds its most 
brilliant expositor in Dr. Oliver J. Lodge, of University College, Liverpool, 
whose experiments made plain the important part which the momentum 
of an electric current plays, especially in discharges like those of the 
lightning flash, and all discharges that are of very high potential and oscilla- 
tory in character. The fourth period is that of the present time, when 
individual flashes are studied ; and protection entirely adequate for the 
particular exposure is devised, based upon some knowledge of the electrical 
energy of the flash, and the impedance offered by appropriate choke coils 
or other devices. For example, under actual working conditions, with 
ordinary commercial voltages, effective protection to electrical machinery 
connected to external conductors may be had with a few choke coils in 
series with intervening arresters. 

A good idea of the growth of our knowledge of the nature and behavior 
of the lightning flash may be obtained from the following publications : 

Franklin's letters. 

Experimental Researches. . . . Faraday. 

Report of the Lightning Rod Conference, 1882. 

Lodge's " Lightning Conductors and Lightning Guards," 1892. 

"Lightning and the Electricity of the Air." . . . McAdie and Henry, 



FIG. 1 EFFECT OF THE ACTION OF LIGHTNING 
UPON A ROD. 

That a lightning rod is called upon to carry safely to earth the discharge 
from a cloud was made plain by Franklin, and the effect of the passage of 
the current very prettily shown in the melting of the rod and the point 
(aigrette). 

Here indeed was a clew to the measurement of the energy of the lightning 
flash. W. Kohlrausch in 1890 estimated that a normal lightning discharge 
would melt a copper conductor 5 mm square, with a mean resistance of 0.01 
ohm in from .03 to .001 second. Koppe in 1895 from measurements of two 
nails 4 mm in diameter fused by lightning, determined the current to be 
about 200 amperes and the voltage about 20,000 volts. The energy of the 
flash, if the time be considered as 0.1 second, would be about 70,000 horse 
power, or about 52,240 kilowatts. 

Statistics show plainly that buildings with conductors when struck by 
lightning suffer comparatively little damage compared with those not pro- 
vided with conductors. The same rod, however, cannot be expected to 
serve equally well for every flash of lightning: There is> great need of a 
classification of discharges based less upon the appearance of the flash than 
upon, its electrical energy. Dr. Oliver J. Lodge has made a beginning with 

701 



702 LIGHTNING CONDUCTORS. 



his study of steady strain and impulsive rush discharges. " The energy 
of an ordinary flash," says Lodge, " can be accounted for by the discharge 
of a very small portion of a charged cloud, for an area of ten yards square 
at the height of a niile would give a discharge of over 2,000 foot-tons 
energy." 

We must get clearly in our minds then the idea that the cloud, the air, 
and the earth constitute together a large air condenser, and that when the 
strain in the dielectric exceeds a tension of £ gramme weight per square 
centimeter, there will be a discharge probably of an oscillatory character. 
And as the electric strain varies, the character of the discharge will vary. 
Remember too that the air is constantly varying in density, humidity and 
purity. We should therefore expect to find, and in fact do, every type of 
discharge from the feeble brush to the sudden and terrific break. Recent 
experiments indicate that after the breaking-down of the air and the pas- 
sage of the first spark or flash, subsequent discharges are more easily ac- 
complished ; and this is why a very brilliant flash of lightning is often 
followed almost immediately by a number of similar flashes of diminishing 
brightness. The heated or incandescent air we call lightning, and, these lines 
of fracture of the dielectric can be photographed ; but the electrical waves or 
oscillations in the ether are extremely rapid, and are beyond the limits of 
the most rapid shutter and most rapid plate. Dr. Lodge has calculated the 
rapidity of these oscillations to be several hundred thousand per second. 
Lodge has also demonstrated experimentally that the secondary or induced 
electrical surgings in any metallic train cannot be disregarded ; and, as in 
the case of the Hotel de Ville at Brussels which was most elaborately 
protected by a network, these surgings may spark at nodal points, and ignite 
inflammable material close by. 

W T hile therefore it cannot be said that any known system of rods, wires, 
or points affords complete and absolute protection, it can be said with con- 
fidence that we now understand why " spitting-off " and " side " discharges 
occur ; and furthermore, to quote the words of Lord Kelvin, that " there is 
a very comfortable degree of security . . . when lightning conductors are 
made according to the present and orthodox rules." 

Selection and Installation of Bods.- The old belief that a 
copper rod an inch in diameter could carry safely any flash of lightning is 
perhaps true, but we now know that the core of such a rod would have little 
to do in carrying such a current as a lightning flash, or, for that matter, any 
high frequency currents. Therefore, since it is a matter of surface area 
rather than of cubic contents, and a problem of inductance rather than of 
simple conductivity, tape or cable made of twisted small Avires can be used 
to advantage and at a diminished expense. 

All bams and exposed buildings should have lightning rods with the neces- 
sary points and earth connections. Ordinary dwelling-houses in city blocks 
well built up have less need for lightning conductors. Scattered or isolated 
houses in the country, and especially if on hillsides, should have rods. All 
protective trains, including terminals, rods, and earth connections, should 
be tested occasionally by an experienced electrician, and the total resist- 
ance of every hundred feet of conductor should not greatly exceed one ohm. 
Use a good iron or copper conductor. If copper, the conductor should 
weigh about six ounces per linear foot ; if iron, the weight should be about 
two pounds per foot. A sheet of copper, a sheet of iron, a tin roof, if with- 
out breaks, and fully connected by well soldered joints, can be utilized to 
advantage. 



I l-z*' 



b 
FIG. 2 AND 3 APPROVED CONDUCTORS AND FASTENITiGS. 





PERSONAL SAFETY DURING THUNDER-STORMS, 703 



In a recently published* set of Rules for the Protection of Buildings from 
Lightning, issued hy the Electro-Technical Society of Berlin, Dr. Slaby gives 
the results of the work of various committees for the past sixteen years 
studying this question. The lightning conductor is divided into three parts, 
; — the terminal points or collectors, the rod or conductor proper attached to 
the building, and the earth plates or ground. All projecting metallic sur- 
faces should be connected with the conductors, which, if made of iron, 
should have a cross section of not less than 50 mm square (1.9 sq. inches) ; 
copper, about half of these dimensions, zinc about one and a half, and 
lead about three times these dimensions. All fastenings must be secure and 
lasting. The best ground which can be had is none too good for the light- 
ning conductor. For many flashes an ordinary ground will suffice, but there 
will come occasional flashes when even the small resistance of ^ ohm may 
count. Bury the earth plates in damp earth or running water. The plates 
should be of metal at least three feet square. 

' If the conductor at any part of the course goes near water or gas mains, 
it is best to connect it to them. Wherever one metal ramification ap- 
proaches another, connect them metallically. The neighborhood of small 
bore fusible gas pipes, and indoor gas pipes in general, should be avoided." 

Dk. Lodge. 




FIG. 4 CONDUCTORS AND FASTENINGS. 
(FROM ANDERSON, AND LIGHTNING ROD CONFERENCE.) 



The top of the rod and all projecting terminal points should be plated, or 
otherwise protected from corrosion and rust. 

Independent grounds are preferable to water and gas mains. Clusters of 
points or groups of two or three along the ridge rod are good. Chain or 
linked conductors should not be used. 

It is not true that the area protected by any one rod has a radius equal 
to twice the height of the conductor. Buildings are sometimes, for reasons 
which we understand, damaged within this area. All connections should 
be of clean well-scraped surfaces properly soldered. A feAV Avrappings of 
wire around a dirty water or gas pipe does not make a good ground. It is 
not necessary to insulate the conductor from the building. 

BIBECTIOMi FOR PElHOlTili SJlJEVET* JaUH-IlHS- 

Do not stand under trees or near wire fences ; neither in the doorways of 
barns, close to cattle, near chimneys or fireplaces. Lightning does not, as 
a rule, kill. If you are near a person who has been struck do not give him up 

Electrotechnische Ztschrift, 1901, May 29, ei 



? 04 



LIGHTNING CONDUCTORS. 



as beyond recovery, even if seemingly dead. Stimulate respiration and 
circulation as best you can. Keep the body warm ; rub the limbs energet- 
ically, give water, wine, or warm coffee. Send for a physician. 

TESTS OF IltHTAJSfi ROSS. 

To make the test, first determine the resistance of the lead wire l t and call 
it l v Then connect E x and E 2 as shown in the diagram, call the result R x ; 
then connect E l and E R , call the result R 2 ; connect E 2 and E 3 and call the 
result E s . 

TESTS OF LIGHTNING RODS. 




THIS LEAD MUST BE 

SOLDERED TO THE PIPE 

OR OTHER EARTH SO AS 

TO HAVE NO RESISTANCE 

AT THIS JOINT. 



FIG, 6 DJAGRAM OF CONNECTIONS FOR TEST OF LIGHTNING RODS. 



Now, B 1 = l.+E l -}-E 2 

i? 2 =A + ^ + ^ 3 

B, = E 2 +E, 
solving, we have 



and 
and 



/:, : 



Ii l ±R 2 -R^ 



E 2 : 
E, 



IL-l - El 
:R 2 —l 1 ~E l 



All lightning rods should be tested for continuity and for resistance of 
ground plate each year, and the total resistance of the whole conductor and 
ground plate should never exceed an ohm. 



DETERMINATION OP WAVE FORM OP CUR- 
RENT AND ELECTRO MOTIVE FORCE. 



A.C. TERMINALS 



Theke are numerous methods of determining wave form, those used in 
laboratory experiments commonly making use of the ballistic galvanometer. 
Of the simple methods used in shop practice, R. D. Mershon, of the West- 
inghouse Electric and Manufacturing Co., has applied the telephone to an 
old ballistic method in such a manner as to make it quite accurate and 
readily applied. 

Hershon's Method. — The following cut shows the connections. A 
telephone receiver, shunted with a condenser, is connected in the line from 
the source of current, the wave form of which it is wished to determine. A 
contact-maker is placed in the other leg, and an external source of steady 
current, as from a storage battery, is opposed to the alternating current, as 
shown. The pressure of the external current is then varied until there is 
no sound in the telephone, when the 
pressures are equal and can be read 
from the voltmeter. The contact- 
maker being revolved by successive 
steps, points may be determined for an 
entire cycle. 

Duncan's Method. — Where it 
is desirable to make simultaneous de- 
terminations it will ordinarily require 
several contact-makers, as well as full 
sets of instruments. Dr. Louis Dun- 
can has devised a method by which one 
contact-maker in connection with a 
dynamometer for each curve will ena- 
ble all readings to be taken at once. 
The following cut shows the connec- 
tions. The fixed coils of all the dy- 
namometers are connected to their 
respective circuits, and the fine wire Fig. 
movable coils of about 1,000 ohms each, 
are connected in series with a contact- 
maker and small storage battery. The contact-maker is made to revolve in 
synchronism with the alternating current source. Now, if alternating cur- 
rents from the different sources are passed through the fixed coils, and at 
intervals of the same frequency current from 
the battery is passed through the movable coils, 
the deflection or impulse will be in proportion 
to the instantaneous value of the currents 
flowing in tbe fixed coils, and the deflections of 
the movable coils will take permanent position 
indicating tbat value, if the contact-maker and 
sources of alternating current are revolved in 
unison. 

The dynamometers are calibrated first by 
passing continuous currents of known value 
through the fixed coils, while the regular in- 
terrupted current from the battery is being 
passed through the movable coils. 

Myan's Method. — Prof. Harris J. Ryan, 
of Cornell Univei'sity, designed a special elec- 
trometer for use in connection with a very fine 
series of transformer tests. This instrument 
Avill be found described and illustrated in the 
chapter on description of instruments. 

The method of using it is shown in the cut below, in which the contact- 
maker shown is made to revolve in synchronism with the source of alter- 

705 




1. MershOn's method of de- 
termining Wave Form. 




Fig. 2. Duncan's method 
of determining curves 
of several circuits at the 
same time. 



TOG 



WAVE FORM. 



TRANSFORMER 



"S^Jfa 



nating current. The terminals, d d x , of the indicating instruments can be 
connected to any one of the three sets of terminals, a a x b b 1 c c t . 

The terminals, a a x , are for reading 
the instantaneous value of the pri- 
mary impressed E.M.F. ; b b u the 
same value of the current flowing 
through the small non-inductive re- 
sistance, R ; and c c t the same value 
of the secondary impressed E.M.F. ; 
the secondary current being read 
from the ammeter shown. Of course 
if the contact-maker be cut out, then 
all the above values will be Vmean 2 . 



.C. AMMETER 




RYAN ELECTROMETER 



WAVE METEIt. 



Fig. 3. Prof. Ryan's method of ob- 
taining curves of wave form for 
studying transformers. 



The instrument illustrated and de- 
scribed in the following pages has been 
in use in the laboratory of the General 
Electric Company at Schenectady, 
since early in 1896, and is, I think, the simplest form of apparatus yet sug- 
gested for determining wave forms in alternating currents. 

The General Electric Company very kindly furnished the following de- 
scription, and the diagrams and illustrations accompanying it. 




Fig. 4. 



This device consists of a synchronous motor intended to run in synchro- 
nism with the machine under test. On the shaft of the motor is placed a 
contact device similar to the contact device usually placed directly on the 
shaft of the generator. By the use of a synchronous motor, the device be- 
comes much more flexible, and enables the Avave to be taken on any part 
of any alternating current circuit by merely attaching a pair of lead wires, 
thus doing away with all mechanical attachments to the generator. 
Since the advent of alternators with a considerable number of poles, the 
old method of mechanical connection has been found to be unsuitable on 
account of the great degree of accuracy required in dividing a cycle into the 
requisite number of degrees, owing to the fact that a complete cycle of 360° 
forms such a small part of the arc of the armature. 
The operation of the machine in detail is as follows : — 
The field requires about 1.35 amperes D. C, and the armature about 4 
amperes for starting. The machine should then be started by means of the 
crank (marked A in Fig. 4) until it has been brought up to the freouency of 
the A. C. circuit, which will be indicated by tachometer (marked H). At 60 
cycles the soeed is 900 R. P. M. As soon as it is in synchronism (which can 
be easily told by the. running of the machine) the lever (marked B) on the 
crank standard should be pressed, which releases the gear mechanism and 
allows the motor to run free. After the machine is running, current in the 
armature should be reduced to 3 amperes. 



WAVE METER. 



707 



The following precautions are necessary in order to procure satisfactory 
working of the apparatus : — 

1. The resistance in all the circuits must be unvarying ; the contact, 
therefore, must be perfect. 

2. The E.M.F. of the A. C. and D. C. circuits must be steady and unchan- 
ging. Complying with No. 1 and No. 2 secures steady currents in all the 
circuits. 

3 Above all, tbe speed of the source must be kept constant ; and if this is 
not possible, readings must be taken only at a certain speed, that speed 
being preferred to which the generator most frequently returns. 

4. Avoid any leads other than shown on the diagram coming in contact 
with the terminals of the D. C. voltmeter. It will be noticed that a con- 
nection between the large and small segments will cause alternating cur- 
rent to flow through the direct current voltmeter. 

5. The tension on the contact spring " F" must be stiff enough to insure 
a good contact. If the brush does not make an even contact on the contact- 
disk, it can be remedied by placing a piece of emery cloth on the contact- 
disk and revolving the brush over the rough side of the emery cloth by 
hand. 

C. The carbon brushes must make as perfect contact on collector rings as 
possible. 

7. In taking a wave, it is recommended that the voltmeter reading should 
vary from a minimum of zero to a maximum of nearly a full scale deflection. 



COMMUTATOR 
CONNECTIONS 

REVOLVING BRUSH 




CURVE SHEET A 



Fig. 5. 



This absolute zero can be obtained by loosening the set screw (marked C) 
on the end of index lever " D." The contact disk, " G," can then be rotated 
on the shaft until the voltmeter reading is at zero, with index pointer set 
on zero degrees. In case the maximum deflection is too low, it can be in- 
creased by either inserting more capacity in the circuit or by using a higher 
voltage on the condenser circuit ; this would be accomplished by using a 
small step-up transformer or compensator at the point marked T in Curve 
Sheet ISo. 8. The transformer voltage should not exceed 150 volts at this 
point. 

8. In case the voltage is too low to give a readable deflection on the volt- 
meter, a D'Arsonval galvanometer can be used in place of the voltmeter. 

9. The oil-cups (marked E) should be kept full of oil, as a thorough lubri- 
cation is found necessary to procure perfect results. 

10. If the machine sparks at contact disk, that is, if spark causes arcing 
from one segment to the following one, it will be necessary to rub the sur- 
face of the disk with fine sandpaper. 

The external wiring connections of the machine are shown on Curve Sheet 
A attached. The connections of the contact device are also shown. This 
consists of a contact-disk with 4 large and 4 small segments. The 4 large 
segments are connected to the inner copper ring on the side of the contact- 
disk. By means of a spring contact and leads the latter is connected to the 
terminal V. Similarly the smaller segments are connected through the 
outer ring and spring contact and leads to the terminal T. 



■08 



WAVE FORM. 



The revolving brush is in contact by means of brush and contact ring as 
seen on the end of the shaft (marked I) to the frame, and from the latter by 
means of wire under the base to the terminal C. 

The principle on which the method is based is the following : When the 
revolving brush, F, leaves the small segment of the contact disk, G, and 
breaks the contact between the condenser and the E.M.F. to be measured, 
it leaves the condenser charged with the potential difference which oc- 
curred at that instant. As soon as the revolving brush touches the large 
segment, the condenser discharges into the voltmeter until the brush leaves 
it. As the speed is constant, the time of discharge is constant, and as the 
discharging circuit is unaltered during the test, the instantaneous E.M.F's 
cause proportional deflections ; the latter follow so quickly as to give steady 
deflections. 

Reading-, Plotting-, and Calculating-. — The movable index- 
pointer is turned till the spring-actuated pin drops into the small hole above 
zero on the fixed scale, and the deflection of the voltmeter noted on a sheet 
of paper having two parallel columns counting the degrees from zero to 360, 
as indicated below : — 



DEFLECTION. 



DEGREE. 



DEFLECTION. 




5 
10 
15 

20 

etc. 



180 
185 
190 
195 
etc. 



175 
180 



355 



After taking the reading at zero, the pointer is moved to 5, then to 10, and 

so on. If after finishing this series of readings a marked difference is noted 

between corresponding deflections in the left and right hand columns, such 

points must be taken over again. 
The average of the two corresponding deflections is taken, and the results 

are then multiplied by such a constant as to make the maximum = 10. 

These values are plotted as Ordinates, and the corresponding degrees are 

abscissae. See sample test and Curve Sheet B. 

To find the average E.M.F., divide the area 
in terms of squares of the paper used, by 10 
times the actual length of one cycle in terms of 
one side of the same squares, as the maximum 
is plotted to a scale of 10 instead of one. On 
Curve Sheet B the length of the half-cycle = 9 
units, and therefore the area must be divided 

by 90. 

The effective E.M.F. , or Vmean square 2 , is 
the square root of the mean squares of the 
same instantaneous values used before. The 
simplest method of obtaining this is the fol- 
lowing : Plot the same deflections on polar co- 
ordinate paper similar to that used in Curve 
Sheet C, and find the area of the resulting 
curve. 

The effective E.M.F. is then equal to the 
radius of a semi-circle whose area expressed 
in terms of squares of the rectilinear co-ordi- 
nate paper, is equal to the area enclosed by 
the wave plotted on the polar co-ordinate 

paper after being reduced to the same dimensions by multiplying by the 




2 4 6 8 10 12 14 16 1: 
E.M.F. WAVE AT NO LOAD 
EXPERIMENTAL ALTERNATOS 

FIG. 6. Curve Sheet B. 



(rt)2 



m 



ratio of 

To find the area a planimeter is used, or the curve is traced or copied by 
means of carbon paper on paper of uniform thickness, which is then weighed 
on a chemical balance, or in case neither of the above methods is avail- 



SAMPLE TEST. 



709 



able, the area can be found by actually counting the number of squares it 
contains. 

The form factor is the 
ratio of the effective to 
the mean E.M.F. The 
form factor of a sine 
wave is 1.11. 

The amplitude factor 
is the ratio of the max- 
imum to the effective 
E.M.F., which, as the 
maximum is one, is 
equal to the reciprocal 
of the effective E.M.F. 
The amplitude factor 
of a sine wave is 1.414. 

These values are to 
be used in making cal- 
culations for alternat- 
ing currents whose 
wave shapes have been 
determined by means 
of the wave meter in- 
stead of employing the usual values based on the sine curve. The accom- 
panying record sheets give the results obtained with an actual E.M.F. wave 
taken with the machine. In the sample test, columns 2 and 4 give the read- 
ings obtained for the different angular deflections. Column 5 is the average 
of the readings obtained. These values are then multiplied by a constant, 
which in this case is .1127, to give a maximum of 10. The resultant values 
plotted in rectilinear and polar co-ordinates are shown on curve sheets B 
andC. 











IT 'tttrttS 


wmm 




-W\\ Vax^c/0/1 \vV\/v/>/ //n~l~J 
/. \ vTx v\. 7^~^— jo — \=-^\ ^\ y\/ Z\ 



Fig. 7. Curve Sheet C. 



SAMPIE TEST. 

(Nov. 21, 1897.) 

J3.M.J?. Wave of Experimental Alternator. 



No. 1. 


No. 2. 


NO. 3. 


No. 4. 


NO. 5. 


No. 6. 


Degrees. 





—4.5 


180 


—4.5 


—4.5 


— .507 


175 


5 


+2.5 


185 


+2.5 


+2.5 


+ .28 





10 


7. 


190 


7. 


+7. 


.79 


5 


15 


11. ' 


195 


11. 


+11. 


1.24 


10 


20 


21. 


200 


19.5 


+19.75 


2.23 


15 


25 


29.5 


205 


29.5 


29.5 


3.32 


20 


30 


30. 


210 


29.5 


29.75 


3.35 


25 


35 


29.5 


215 


29.5 


29.5 


3.32 


30 


40 


36. 


220 


36. 


36. 


4.06 


35 


45 


51. 


225 


50. 


50.5 


5.695 


40 


50 


71. 


230 


72. 


71.5 


8.05 


45 


55 


72.5 


235 


71.5 


72. 


8.12 


50 


60 


66. 


240 


66. 


66. 


7.44 


55 


65 


70. 


245 


71. 


70.5 


7.95 


60 


70 


85. 


250 


85. 


85. 


9.58 


65 


75 


89. 


255 


88.5 


88.75 


10. 


70 


80 


75.5 


260 


73.5 


74.5 


8.4 


75 


85 


68.5 


265 


67.5 


68. 


7.66 


80 


90 


61.5 


270 


60.5 


61. 


6.87 


85 


95 


59.5 


275 


60. 


59.75 


6.73 


90 


100 


■72. 


280 


72.5 


72.25 


8.15 


95 


105 


81. 


285 


81. 


81. 


9.13 


100 


110 


87. 


290 


87.5 


87.25 


9.82 


105 



710 



WAVE FORM. 



8AMPIE TEST — (Continued). 



No.i. 


No. 2. 


No. 3. 


NO. 4. 


No. 5. 


No. 6. 


Degrees. 


115 


84. 


295 


83. 


83.5 


9.40 


110 


120 


72.5 


300 


73. 


72.75 


8.2 


115 


125 


67.5 


305 


68. 


67.75 


7.63 


120 


130 


77. 


310 


77.5 


78.25 


8.81 


125 


135 


82.5 


315 


82.5 


82.5 


9.3 


130 


140 


60. 


320 


59.5 


59.25 


6.68 


135 


145 


41. 


325 


41.5 


41.25 


4.65 


140 


150 


32. 


330 


32.5 


32.25 


3.64 


145 


155 


30.5 


335 


30.5 


30.5 


3.44 


150 


160 


37.5 


340 


37. 


37.25 


4.2 


155 


165 


30. 


345 


30.5 


30.25 


3.41 


160 


170 


16. 


350 


15.5 


15.25 


1.775 


165 


175 


8.5 


355 


9.0 


8.75 


.98 


170 



The different constants of this wave are given below in "Method of De- 
termining Constants of E.M.F. Curve." This also gives the constants for a 
sine wave for comparison. 

SPECIAL DATA ©]¥ THE MOTOR ILLUSTRATED. 

Resistance of field = 10.87 ohm. 
Resistance armature and brushes = 2.055 ohm. 

Armature alone = .560 ohm. 
Armature winding — 14 turns of No. 28 D. C. C. copper wire doubled in 
each slot. 
Field frame consists of & H.P. IT. I. Fan Motor — 125 cycles, 104 volts. 



METHOD OF DETERMI^IIVG CO]¥STA3fTS OE 

E.M.E. CURVE. 



Area Rect. Co-ord. Curve " B " = 51.32. 



51 32 
Mean E.M.F. = „ * = .571. 



9X 10- 



(11 33 \ 2 
- ' ) to be com- 
parable to the area in rectilinear co-ordinates. 11.33 is the maximum ordi- 
nate of the rectilinear co-ordinate in centimeters, and 8.95 is the maximum 
ordinate of the polar co-ordinate curve ; therefore the corrected polar area 
= 40.62 X 1.6 = 64.992. 
Now \irf'- — 64.992, therefore r = .643, which is the effective E.M.F. 



The form factor being therefore 
The amplitude factor — 



effective 

mean 

maximum 

effective 



.643 

.571 

1 

^643 



= 1.127. 
= 1.554. 



For comparison the constants of a sine wave are also given in the recapit- 
ulation below. 

Mean Effect. Form Amp. 

e.m.f. e.m.f. factor. factor. 

Rect. Co-ord. Curve B 51.32 ) - 71 -.o ■, 197 -1^4 

Polar " " C 40.62} -° 71 ' iAd 1127 1,5 ° 4 

Sine Wave . 637 .707 1.110 1.414 



CERTAIN USES OP ELECTRICITY IN THE 
UNITED STATES ARMY. 

Electricity enters into nearly every branch of the military art, being used 
for the operation of searchlights, turret-turning, manipulation of coast-de- 
fense guns, ammunition hoists, range and position finders ; for firing sub- 
marine mines ; field and fortress telephones and telegraphs ; firing devices 
for guns, ground mines ; in tide gauges ; submarine boats and dirigible tor- 
pedoes ; while electrically operated chronographs are employed in the solu- 
tion of ballistic problems. 

SEARCHLl&HTi. 

Searchlights are used both as offensive and defensive auxiliaries ; defen- 
sive when used by shore fortifications to light channels or by a vessel to 
discover the approach of torpedo boats ; offensive when used as " blinding- 
lights " to smother the light of an approaching vessel and confuse her pilot. 

The accompanying illustrations show the searchlight manufactured by 
Schuckert & Go. of Nurnberg, Germany. 

The lamp is placed on top of the two lowest longitudinal rods of the cas- 
ing, and is held in place by four lugs, two on each side. The carbon holders 
reach upward through a slit in the casing, and there is a small wheel in rear 
for moving the light parallel to the axis of the reflector, for the purpose of 
focusing it. The trunnions of the casing are fastened to two longitudinal 
rods on each side, parallel to the axis of the cylinder, and can be moved for- 
ward or back so that the casing and what is carried with it will have no pre- 
ponderance. The trunnions are supported in trunnion beds in the ends of 
supports which project upwards from the racer. 

The elevating arc is attached to another longitudinal rod beneath the 
cylindrical casing and is capable of adjustment on this rod. Engaging in 
this arc is a small gear attached to a horizontal shaft passing through the 
right trunnion support and carrying a small hand wheel. This small hand 
wheel is for the purpose of elevating or depressing the light rapidly. 

The light may be elevated or depressed slowly by means of a small hand 
wheel attached to another horizontal shaft in front of the one just described. 
This shaft near its center carries a worm, engaging in a worm wheel on a 
vertical shaft, to which is also attached a bevel gear. This gear engages in 
another, which is attached to the quick- motion shaft, but is free to turn 
about it until it is connected with the elevating gear wheel by means of a 
friction clamp. The relation between the worm and worm wheel is such 
that a slow motion is obtained. 

The racer rests upon live rollers and is joined by a pintle to the base ring. 

Attached to the base ring is a toothed circular rack, into which on the 
outside a gear wheel attached to a vertical shaft engages. This vertical 
shaft projects upward through the racer and carries a worm wheel, which 
engages in a worm carried on a horizontal shaft having a hand wheel. The 
worm wheel is entirely independent of its vertical shaft, except when con- 
nected with it by means of a friction clamp. When so connected, by turn- 
ing the hand wheel the light is traversed by a slow motion. To traverse 
the light rapidly, the friction clamp is released and the light turned by 
hand, taking hold of the trunnion supports. One of the ends of the slow 
motion elevating and traversing shafts is connected with a small electric- 
motor, which is encased in a box on top of the racer. By means of these 
motors the motion of the searchlight can be controlled from a distant point. 
A switch is provided with contacts so arranged that the current can be 
passed into the armatures of the motors in either direction, so as to obtain 
any movement the operator may desire. The current needed for the move- 
ment is obtained from the lines supplying the current used in the light itself . 
The current is brought to the motors by means of contact points, bearing 
on circular contact pieces attached to the racer. 

The reflector is a parabolic mirror embedded in asbestos in a cast-iron 
frame, and is held in place by a number of brass springs. The frame of the 
reflector is fastened to the overhanging rear ring of the casing with studs 
and nuts, the overhanging part of the ring protecting the reflector from 

711 



712 CERTAIN USES OF ELECTRICITY IN U.S. ARMY. 




Fig. 1. Schuckert Searchlight as used in U. S. army. 



moisture. In order to enable the operator to observe the position of the 
carbons and the form of the crater while the apparatus is in use small 
optical projectors are arranged at the side and on top of the casing, which 
enables images of the arc as seen from above and from the side to be 
observed. When the light is properly focused the positive carbon reaches 
a line on the glass on top of the casing. 

There are two screws on the positive carbon holder which enable the end 
of this carbon to be moved vertically or horizontally to bring it to a proper 
adjustment. 

In consequence of the ascending heat the carbons have a tendency to be 
consumed on top ; and to avoid this there is placed just back of the arc and 
concentric with the positive carbon a centering segment of iron, attached to 
the casing, which, becoming magnetic, so attracts the current as to equalize 



SEARCHLIGHTS. 



713 



the upward burning of the carbons. In taking the light out of the casing 
this centering segment must be unfastened, and swung to the side on its 
hinge. 




SAFETY FUSE 

Fig. 2. Diagram showing Searchlight Connections. 

An example of the method of calculating the intensity of the light sent out 
by the mirror follows : — 

Diameter of parabolic mirror, 59.05 inches. 

Diameter of positive carbon, 1.5 inches. 

Diameter of negative carbon, 1 inch. 

Power consumed, 150 amperes x 59 volts. 

Maximum intensity of rays impinging upon the mirror, 57,000 candle- 
power. 



14 CERTAIN USES OF ELECTRICITY IN U.S. ARMY 



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CHRONOGRAPHS. 



715 



Average intensity of rays impinging upon mirror, 45,600 candle-power. 

Diameter of crater, 0.905 inch. 

Intensifying power of the mirror, 
/y_ (59.05)2 _ 
cP ~ (0.905) 2 — ' 

Total intensity of light sent out hy 
mirror, 45,600x4,253=194,000,000 can- 
dle-power. 

The focal distance of the mirror is 25.5 
inches. 

The dispersion angle of the concen- 
trated beam is 2° 2 / . 

The diameter of the illuminated area 
at a distance of 1,111 yards is 84 yards. 

The resistance Bm on the switchboard 
at the light is in series with the main 
current for the purpose of regulating 
the amperage at the lamp. The volt- 
meter at the lamp should indicate about 
60 volts. The connection of the dis- 
tance governor with the two motors for 
elevating and traversing is also shown. 

The largest searchlight so far built is 
the one that Avas on exhibition at the 
Paris Exposition of 1900 in the section 
" Navigation de Commerce et Armees 
de Terre et de Mer," which is 6 feet 6 
inches in diameter, and gives a beam of 
316.000,000 candles. 

The table . on preceding page gives 
data in regard to searchlights of various 
sizes. 

CHRONOGRAPHS. 

In the experimental work of testing 
guns, etc., it becomes necessary to ascer- 
tain the velocity of projectiles both 
while passing through the bore of the 
gun and during flight. Chronographs of 
various sorts are used for this purpose. 

In order to ascertain the velocity of a 
projectile during flight, two screens or 
targets are set up in the course of the 
projectile, generally 100 feet apart. 
These screens ordinarily consist of a 
frame of wood carrying a number of 
small parallel copper wires. The break- 
ing of the wires in the successive frames 
by the projectile causes the interruption 
of the current through the instrument, 
and thus registers the time of flight 
between the screens. 

Probably the best-known instrument 
of this class is the one invented by Cap- 
tain Le Boulenge of the Belgian artil- 
lery, which was afterwards modified by 
Captain Breger. 

Bouleug'e Chronograph. 

This instrument depends for its accu- 
racy upon the law of falling bodies or the 
acceleration due to gravity, namely 32 Fig. 3. 

feet per second. 

It consists of a vertical column (Fig. 3 ) to which are affixed two electro- 
magnets ; the right-hand one, A, is actuated by the current of the first frame 




716 CERTAIN USES OF ELECTRICITY IN U.S. ARMY. 



and supports an armature called the chronometer ; the left-hand magnet, 
B, is actuated by the current of the second frame, and supports an arma- 
ture, I), called the registrar. 

The chronometer, C, is a long, cylindrical brass tube terminating at its 
upper extremity in a piece of soft iron, and bearing at its lower extremity a 
steel bob. It is surrounded by a zinc or copper cylinder called the recorder, 
The rupture of the first target causes the demagnetization of the magnet A, 
releasing the rod C. The registrar is of the same weight as the chronome- 
ter, and is a tube with soft iron and bob. The cores of the electro-magnets 
and the soft iron of the armatures terminate in cones slightly rounded at 
their vertices in order that the armatures when suspended can take a verti- 
cal position. 

When the registrar is set free by the rupture of the second target it 
strikes a horizontal plate (a), which turns upon its axis (c) and releases the 
spring (d). The spring is furnished with a square knife (e), which strikes 
the recorder and leaves an indentation upon it. 

If the two currents be ruptured simultaneously the indentation is found 
upon the recorder at a height h, indicating that since the chronometer 

commenced to fall the time t has elapsed, t =z 4/ . — . 



It is evident that t is the time required for the apparatus to operate ; it 
is a systematic retardation inherent in the instrument. 

A special device, called the disjunctor, permits the simultaneous rupture 
of the circuits to be produced, so that the time t is always known. 

A very simple device is resorted to in order to render it constant. If the 
current of the registrar is not ruptured until after that of the chronometer, 
and if an interval T has elapsed between these ruptures, the time during 
which the chronometer will fall before receiving the indentation of the 
knife will simply be augmented by t, and calling H the height of the inden- 
tation, we will have ,- 
t+T=zyfl 



'2H 



Thus the determination of an interval T always comprises two opera- 
tions : the measurement of the time (t) required for the instrument to 
operate, and that of the time t -j- T. The difference of these two measure- 
ments gives the time sought. This indirect method of ascertaining the 
result is the characteristic of the instrument and explains its accuracy. 
When the rupture of the currents is produced by the projectile the portion 
(D) of the trajectory between the targets is regarded as rectilinear and the 
mean velocity V is j) 



V- 



VJ<- 



■h) 



The arrangement of the circuit must vary according to circumstances, 
and no particular system can be prescribed. The general arrangement, 
however, is shown in the sketch 




FlG. 4. Connections of Boulenge Chronograph. 



CHRONOGRAPHS. 



717 



Schultz Cbronoscope. 

The Boulenge chronograph measures velocity at one point only, but it is 
frequently necessary to measure the velocity of the same projectile at 
different points as in determining the laws of the resistance of the air to its 
motion, or in ascertaining the velocity of a projectile at different points in 
the bore. 







Fig. 5. Schultz Chronoscope. 



For such purposes an instrument must be used which will give a scale of 
time of such length that all the phenomena may be registered upon it. 

There are several instruments of this class, of which the best known is the 
Schultz chronoscope. In this instrument a drum (a), one meter in circum- 
ference, and covered with a coating of lamp-black, is driven by the means 
of a clock movement and weight, so as to revolve once per second and 
at the same time slowly advance longitudinally. In front of the drum, 
mounted on a support and actuated by two magnets, is a standard tuning- 
fork (c), vibrating 250 times a second ; on one link of this fork is a quill (6) 
which traces aline on the blackened surface of the drum, and therefore 
will record 250 complete vibrations for every revolution of the drum. 

A telescope with micrometer (not shown in drawing) is also attached to 
the support fork ; and each vibration of the fork, traced on the drum in form 
of a curve, can be subdivided in 1000 parts, thus allowing readings to be 



made to 



of one second. On the support with the tuning-fork is a 



small pointer which traces a straight line on the drum. This pointer has an 
electrical connection with an accurate chronometer which at every half- 
second closes the circuit and causes the pointer to make a succession of 
records on the revolving drum. These marks serve as starting-points to 
count the number of vibrations of the tuning-fork, and to check them up 
every half-second. 

In order to measure the velocity of projectiles, the gun must be fitted 
along its bore with special electrical circuit breakers, usually placed one 
foot apart. Each circuit breaker is so constructed that the current is 
interrupted as the projectile passes, but is made again before the projectile 
reaches the next breaker one foot farther on. 

These breakers, with appropriate battery, are all in one circuit with the 
primary of an induction coil. One terminal of the secondary of the coil is 
grounded to the frame of the chronoscope, udiile the other terminal con- 
sists of a fine point near the blackened surface of the drum. Therefore, 



718 CERTAIN USES OF ELECTRICITY IN U.S. ARMY. 



when the primary circuit is opened by the first circuit breaker along the 
bore of the gun, the spark induced in the secondary of the induction coil 
jumps from the points to the revojving drum, leaving a distinct mark on 
the blackened surface As the next circuit breakei in the gun is passed, 
the spark again passes to the drum, and this operation is repeated for every 
breaker along the gun bore. Thus on the drum, alongside of the indications 
made by the tuning-fork, will be recorded a succession of spots at certain 
distances from each other. The time elapsing between any two of these 
spots can be calculated directly from the record which the tuning-fork 
made, and thus the time (measured to the gso^oo part of a second) taken by 
the projectile in passing a known distance along the gun barrel calculated. 
— Electrical World and Engineer, June 23, 1900. 

Schmidt Chronograph. 

This is a portable instrument, and while probably not so accurate as the 
Boulenge instrument is sufficiently so for the every-day work of the proving- 
ground. 

The chronograph is composed of the following principal parts (see Figs. 
6 and 7) : 




Fig. 6. Connections of Schmidt Chronograph. 

The balance-wheel A with its spring and needle. 

The electro-magnet B, which holds the balance-wheel at the starting- 
position and releases it the instant the first current is broken. 

The electro-magnet C, with its mechanism, which stops the balance-wheel 
the instant the second current is broken. 

The dial D, graduated for velocity readings. 

A circular frame E, for setting tlie instrument at zero. 

The button F, reestablishing the current in the magnet C. 

The rheostats G and G', with their resistance coils for regulating the 
currents. 

The balance-wheel, made of nonmagnetic metal, is about 1\ inches in 
diameter and mounted on the axis o, which is held by two strongly made 
bridges fastened to the face plate of the instrument. The pivots of the 
axis are set in jeweled bearings. The spiral spring //is fastened to the 
bridge and axis as in ordinary chronometers. 

The needle, /, is composed of two parts, as shown in Fig. 8. One part, a, of 
bronze, is fastened rigidly to the axis; the other, b, a steel spring, is 
fastened at one end to a, the free end being limited in its motion by two 
small pins set into a. 

The electro-magnet B, which holds the balance-wheel at the starting- 



CHR0N06KAFHS, 



719 



point, is operated by the current passing through the first screen, and is 
mounted on the face piale so that the core is radial with reference to the 
balance-wheel. The core of the magnet projects beyond the coil and acts 
upon the small armature c, mounted on the rim of the balance-wheel. 

The electro-magnet C, with its mechanism operated by the current pass- 
ing through the second screen, stops the balance-wheel the instant the 
current is broken. This magnet is somewhat larger than the other, and is 




Interior Schimdt Chronograph. 



placed tangentially Avith reference to the balance-wheel. It acts upon the 
two armatures d, d', placed opposite the extremities of the core. These 
armatures are fastened to the ends of the two levers A', K', which are 
mounted on the axis e, e', parallel to the axis of the balance-wheel and 



Fig. 8. Construction of Needle. 



similarly supported. The other ends of the levers are joined by the coiled 
spring L with its adjusting-screw. Set in the levers near this end are four 
pins,/,/,/',/', that ordinarily, due to the tension of the spring, bear against 



720 CERTAIN USES OF ELECTRICITY IN U.S. ARMY. 

the rim of tlie balance-wheel, holding it fast. When the current passes 
through this magnet, the armatures on the levers are attracted by the 
core, the spring is elongated, and the pressure of the pins upon the balance- 
wheel is released. When the current is broken the armatures are released, 
and the tension of the spring closes the pins upon the wheel. To insure 
effective action the pins are accurately set and the rim of the wheel is 

The face of the chronograph is a graduated dial concentric with the 
balance-wheel axis. When the wheel is held at its starting-point the needle 
points at the zero of the graduation. The scale in black indicates the time 
in thousandths and two-ten-thousandths of a second. Another scale, in red, 
gives the velocity directly in meters per second when the screens are placed 
50 meters apart. . . 

The dial is covered with glass inclosed in the circular metal frame E. 
A pin, q, fixed in the glass, is used to set the needle at zero by turning the 
frame, to which is also fastened the lens h, to facilitate reading. This lens 
is provided with two pointers so placed that the reading is always taken in 
the vertical plane. 

The button F is for the purpose of reestablishing the current through 
the magnet C after it has once been broken. Pressing the button closes 
the circuit ; the magnet then attracts the armatures d, d', fixed to the ends 
of the levers K, K'. This motion of me levers brings the small spring I, 
mounted on K f , in contact with the projection k, thus forming a circuit 
through which the current continues to flow after the pressure on F has 
been released. This contact is broken by the motion of the lever when the 
current is interrupted by the shot. This arrangement prevents the current 
from passing through the magnet and releasing the balance-wheel before 
the circuit is closed by pressing the button F, even though the broken screen 
is repaired, and gives the operator time to take the reading and prepare for 
the next shot. This is especially important when targets that close the 
circuit automatically are used. 

The rheostats for regulating the currents are placed above the dial, their 
resistance coils being inside the case. One binding-post of each rheostat is 
provided with a circuit closer for passing the currents through the resis- 
tance coils or directly into the rheostats. 

Tiie Squire-Creliore Photo-Clironog-rapti. 

This instrument was designed to overcome the minute errors inherent in 
other forms of chronographs, such as the inertia of the amature, the time 
required to magnetize iron, or in instruments employing a sparking de- 
vice, the fact that successive sparks do not proceed from the same point by 
identically the same path. 

The agents employed in this instrument are light and electricity. Briefly 
stated, a ray of light from an electric arc is reflected upon a revolving 
photographic plate. The interposition of a tuning-fork gives on the plate 
a curve which is used as a scale of time. 

In the path of the beam of white light is placed a Nicol prism in order to 
obtain a beam of plane polarized light. This prism is made of two crystals 
of Iceland spar, which are cemented together by Canada balsam in such a 
way as to obtain only a single beam of polarized light. The crystal is a 
doubly refracting medium ; that is, a light beam entering it is in general 
divided into two separate beams which are polarized and have different 
directions. One of these beams in the Nicol prism is disposed of by total 
reflection from the surface where the Canada balsam is located, and the 
other emerges a completely polarized beam ready for use. 

A second Nicol prism exactly like the first is now placed in the path of 
the polarized beam. This second prism is called the " analyzer," and is 
set so that its plane is just perpendicular to that of the first prism, called 
the " polarizer," so that all the light vibrations not sorted out by the one 
prism will be by the second. In this position, the planes being just perpen- 
dicular to each other, the prisms are said to be " crossed," and an observer 
looking through the analyzer finds the light totally extinguished as though 
a shutter interrupted the beam. 

By turning the analyzer ever so little from the crossed position, light 
passes through it, and its intensity increases until the planes of the prisms 
are parallel, when it again diminishes ; and if one of the prisms is rotated 



MANIPULATION OF COAST-DEFENSE GUNS. 721 

there will be darkness twice every revolution. In order to accomplish this 
same end without actually rotating the analyzer a transparent medium 
which can rotate the plane of polarization of the light subject to the con- 
trol of an electric current is placed between the two prisms. The medium 
used is carbon bisulphide contained in a glass tube. To produce a mag- 
netic held in the carbon bisulphide a coil of wire through which passes an 
electric current, is wound around the glass tube. When the current ceases 
the carbon bisulphide instantly loses its rotatory power, and the ray of 
light is free to pass through the prisms. 

Breaks in the current are made in the same way as in other ballistic 
chronographs. For a complete description of this instrument, with an 
account of experiments, see The Polarizing Photo-Chronograph, John 
Wiley & Sons, New York. 

MAMPlILAXIOHr ©:F C0AST>DXFEITSE CH7MTS. 

Until recently all gun carriages installed in the coast fortifications of the 
United States were designed for the use of hand power iu their manipula- 
tion. Tests, however, having demonstrated the adaptability of electrical 
power for this purpose, such guns are now being equipped with electric 
motors. 

The following data is taken from recent tests of the equipment of a 10- 
inch disappearing carriage. 

The equipment installed consists of : 

One 3 h.p. motor connected directly by spur gearing to the crank shaft of 
the traversing mechanism. 

One 5 h.p. motor for operating both the elevating mechanism and the 
retraction gear. 

A hand brake applied to a drum on main crank shaft of traversing gear. 

Control switches, wiring, etc. 

The iron-clad motors and switch boxes are water and dust tight. The 
mechanical hand brake is used to overcome the tendency of the carriage to 
settle back when stopped quickly at a particular point, due to the great 
weight and inertia. 

The weight of the gun is 67,000 pounds, and moving parts of carriage, 
approximately 170,000 pounds, a total of 237,000 pounds. 



TRAVERSING MOTOR. - 



Results. 

130 volts. 



AtMHpeed, jgwjp-tj-gfc 

U-8 effective H.P. 
fll9 volts. 
At half speed. J g am £ eres JO*** 

(2.9 effective H.P. 
fl20 volts. 

Sl°we StS peed. JSS$SSS£SS. 

1.2.4 effective H.P. 

Time required to traverse through entire field of fire, 106° 30' twenty-five 
seconds [of time]. 

ELEVATING AND RETRACTING MOTOR.— 

f 128 volts full speed. 
In depressing through extreme J 13 amperes full speed, 
range, + 15° to — 5°. 1 1.8 effective H.P. 

(^Time, 22 seconds. 
fl22 volts full speed. 
In elevating gun through ex- J 20 amperes, full speed, 
treme range. | 1.8 effective H.P. 

^Time, 22 seconds. 



722 CERTAIN USES OF ELECTRICITY IN U.S. ARMY. 



RETRACTION. 



1 120 volts full speed. 
| 20 amperes full speed. 
( Tune, 2 min. 2 sec. 



To bring gun from firing to 
loading position. 

A more complete description of this apparatus may be found in the 
Electrical World and Engineer, January 19, 1901. 



ELECTRIC FUSES. 

It is often necessary to fire at a distance from the gun, as in experiments, 
and for this purpose electric fuses are used. 

The fuse consists of a J-inch length of fine wire of platinum-iridium alloy, 
called the bridge, surrounded by a little gun-cotton or powder ; next to this 




Fig. 11. Firing Key. 



A, copper case. 

B, hollow wood cap, 
CC, wires, .035 inch. 
D, bridge, .0025 inch. 
F, priming. 

H, fulminate of mercury, 

10 to 24 grains. 
I, paper discs held by 

drop of collodion. 
K, plug of beechwood. 



A, copper case. 

B, plug (beechwood). 

C, insulated wires. 

D, bridge. 

F, gun-cotton priming. 
H, rifle powder. 
I, cotton string. 
K, tin foil cap. 



LyJ 



K 



Figs. 9 and 10. Electric Fuses. 



is placed, when required for detonating, a few grains of fulminate of mer- 
cury. The whole is usually fixed inside a copper case. The bridge being 
inserted in an electrical circuit is heated by the current which ignites the 
gun-cotton and fires the fuse. 

Fig. 9 shows a gun-fuse. Fig. 10 is a mine-fuse, which is similar in con- 
struction, and is used in firing high explosives, or where it is desired to 



DEFENSIVE MINES. 723 



ignite several charges simultaneously, as in a group of submarine mines. 
Fig. 11 shows the tiring-key, in which T is a turnbuckle of ebonite which 
prevents accidental closing of the circuit. 

»EF1L\«IVE MINES. 

A mine is a charge of explosive contained in a case which is moored be- 
neath the surface of the land or water. The mines laid and operated in and 
around seacoast fortifications are for the most part defensive in their char- 
acter, fixed in position, and hidden. 

A defensive mine is either self-acting, — a mine which, once placed, ceases 
to be under control, and is fired by means within itself, mechanical or elec- 
trical,— or controlled, a mine fitted with electrical apparatus, which ena- 
bles a distant operator to ascertain its condition, and to fire it at any time ; 
it may also be tired automatically. 

A controlled mine may be tired in four different ways : (a) by contact with 
the mine only ; (b) at will of the operator only ; (c) by contact and will, both 
of which are necessary ; (d) by observation from two stations. 

A controlled sea mine may be either a buoyant mine whose case floats 3 
or 4 feet beneath the surface, and contains both the charge and electrical 
apparatus, or aground mine. The latter is in two parts: one a case contain- 
ing the charge and fuse, rests on the bottom ; the other, containing the elec- 
trical apparatus, floats 3 or 4 feet beneath the surface. 

Copper wires lead to two or three Sampson-Leclanche cells, which are 
put in circuit with the torpedo casemates of the fortification. 



>.Y/'». <L_iiiiz 1 /ki^dL a!/m^!! 





SPRING BOARD 


, 75 ' _ || 




| AJ 

1 B? 


LE CLANCHE 1 






I 



'FUSE 
EXPLOSIVE 



20 

Fig. 12. Electrical Land Mine. 

The sketch shows a self-acting electrical land mine, and is self-explana- 
tory. By using three lead wires the mine may be fired by the enemy's con- 
tact with it, or by the operator at the station. 

Circuit Closer in Torpedo. 

(See Fig. 13.) 

NS, circular permanent magnet with attached electro-magnets N and S. 

A, armature whose adjusting spring near K holds it away from the mag- 
net, while a weak current flows in through the electro-magnet coils in a 
direction to assist the permanent magnet. But if a stronger current flows, 
the armature is attracted, and sticks to the magnet, until a reverse current is 
sent in. The spring then draws the armature away, and breaks the contact 
of the circuit closer K on W. 

B, a brass ball | inch diameter, held by spiral S. 

T, a silk thread running through the vertical axis of the ball from adjust- 
ing screw to the armature. When the vessel strikes the mine the brass ball 
being knocked sidewise pulls, by means of the string, the armature against 
the poles where it sticks. 

R, 1000-ohm resistance coil, which is cut out of the mine circuit by the 
contact of K on W. 

PC, priming-charge. 

F, fuse. 



724 CERTAIN USES OF ELECTRICITY IN U.S. ARMY. 



Operating-Box on Shore. 

WB', watching-battery of gravity cells and brass bar. 

FB', tiring-battery of Sampson cells and. brass bar. 

P', firing-plug. 

M / M / , ordinary electro-magnet, 100 obms. (See Relay No. 7.) 

A', armature pivoted at tbe center. (See Relay No. 7.) 

S', spring holding armature back against a weak current. (Relay No. 7.) 

I/, shutter arm pivoted above its center of gravity. When set as in relay 
No. 1, shutter-arm L/ makes electrical connection with the armature at N / ; 
when armature is attracted it releases I/, whose lower end strikes a bell, and 
makes electrical contact with the tiring-bar at B'. 

b, terminal of mine circuit which may be plugged to WB'. 

a, terminal for testing-set. 

o, o, two rever sing-keys. 

Xand Y are two stations, 1 to 3 miles apart, each having a key and an ob- 
server of the mine field. 

Operation. 

The torpedo having been planted and connected with its relay, whose 
shutter-arm 1/ is set as in relay No 1, a small steadv watching-current flows 
through G', WB', b, M'M', H, N', J', O', V, coil S, coil, N, W, R (1,000 ohms), 
G to G/ again. The direction of the current is such as to preserve the mag- 
netism of the magnet. If the circuit closer is accidentally closed (indicated 
by a change of the resistance in the circuit) it can be opened by using the 
reversing-key from shore. 

The fuse F may be fired in four ways : — 

(a) By contact with the mine only. Insert firing-plug P'. When a vessel 
strikes a mine the brass ball B in the circuit-closer is thrown aside, closing 
K on W and thus short circuiting R. The watching-current, thus made 
stronger, flows from coil N through K, A, Z, fuse, G„ to G'. Coming from 
gravity cells it cannot fire the fuse, but is strong enough to operate the relay 
and drop I/, which throws in the firing-battery. A strong current now flows 
through G", FB', P', B', J', O', V, coil S, coil N, W, K, A, Z, F, G„ to G" 
again, and fires the fuse. 

(6) At will of operator only, who may at any time drop the shutter arm 1/ 
by hand and insert the firing-plug. The firing-current is strong enough, 
even through R in the torpedo, to close K, short-circuiting R, and to fire 
the fuse, 

(c) By contact with the mine and at operator's will. Remove firing-plug 
P'. The watching-current flows as above in (a). When the vessel strikes 
the mine 1/ drops, striking the bell, when the operator inserts P', throwing 
in the firing-current which fires the mine. 

(d) By observation from two stations ; shutter arm 1/ set, and firing-plug 
P' in. When a hostile vessel appears over the mine from the position of X 
the observer closes his key. Y has like instructions. When both keys are 
closed the main part of the current from WB' flows through G', WB', b, 
M'M', H, Q/, X, Y, G, to G' again, drops the shutter-arm and fires the mine. 

For obvious reasons the foregoing is not a description of the service cir- 
cuit closer, but the principle of construction and operation of the mines of 
all countries are much alike. 

MISCELLAXEOFS. 
Fortress Telephones and Telegraphs. 

Covering as it does a considerable area, the modern fortification must Lave 
its several units within instant communication, in order to insure that con- 
cert of action so necessary to a successful command. The fort commander 
must communicate his orders to the battery commanders, and they in turn 
transmit the necessary commands to the gun commanders ; and while much 
time and ingenuity has been spent in devising means of communication 
through the medium of printing and dial telegraphs, the telephone is to-day 
practically the universal method of communication from one part of a fire 
command to another. As ordinary commercial telephones are employed, no 
special description of them need be given in this section. The telephone is, 
however, at best, but an unsatisfactory method of communication, and will 
be rendered more so by the noise and confusion of battle. 



DEFENSIVE MINES. 



725 



CIRCUIT CLOSER 
IN TORPEDO 




OPERATING BOX ON SHORE 
Eig. 13. Diagram of torpedo circuit closer and connections 



^3 



26 CERTAIN USES OF ELECTRICITY IN U.S. ARMY. 



field Telephones and Telegraphs. 

But little is to be said of field telephones and telegraphs, as they do not 
differ from commercial instruments except in their portability. The wire 
is carried on reels mounted on wheeled trucks, and may or may not be 
strung on poles as the occasion demands. Light reels are also provided 
which may be strapped to a man's back to run wires to places otherwise in- 
accessible. The work to be done by field telegraphers is, however, an im- 
portant one in keeping a commander constantly >.n touch with his outposts. 



ELECTRICITY IN THE UNITED STATES 

NAVY. 

The application of electricity in ships in the United States Navy at the 
present time (July, 1901) is as follows : — 

All ship's lights, searchlights, and signal lights are entirely electric. 

Of power appliances the turret turning, elevating and loading of big guns, 
and hoisting ammunition, are always done electrically ; ship's ventilation 
is partly steam and partly electric, with the practice rapidly going to 
complete electric ; deck Avinches and boat cranes are usually steam, but 
very successful electric ones are in use ; steering-gear is entirely steam, 
hydraulically or mechanically controlled, and electric appliances are in the 
experimental stage ; an electric system of opening and closing water-tight 
doors is now in progress of development ; anchor-handling gear is entirely 
steam. 

Interior communication appliances are almost entirely electric, but are 
in some cases paralleled with mechanical equivalents, as for example voice 
tubes paralleling telephones. 

M\ino ROOM. 

The generating plant is located in a compartment called the " Dynamo 
Room," which is under the protective deck and adjacent to the boiler 
rooms, so as to secure a direct lead of steam pipes. 

GEKERATIHO-SETi. 

The following are the principal requirements contained in the standard 
specifications for generating-sets : — 

Generators. 

Generators to be of the direct current compound-wound multipolar type, 
giving 80 volts at the terminals. The compounding to be such that at the 
designed normal speed the voltage shall at no point of the external char- 
acteristic curve vary more than 1.5 volts from 80 volts. 

There shall be no sparking whatever at the brushes when the generator 
is in operation with a constant load, nor shall there be any detrimental 
sparking with a change of one-half load, the brushes not being moved. 

The allowable temperature rises above the air after a four-hour run at 
full load are : — 

Field and armature windings 60° F. 

Commutator 72° F. 

The temperature of windings to be calculated from their resistance rise, 
and of the commutator to be measured by thermometer. 

Generator to stand an over-load of 33 per cent for two hours without 
injury, and the engine to be able to produce normal voltage with this over- 
load. 

Insulation resistance to be one megohm, tested with a pressure not greater 
than 1000 volts. 

The change of voltage at the terminals of the generator as measured on a 
dead-beat voltmeter not to exceed 10 volts, when full load is suddenly 
thrown on or off. 

External magnetic field to be inappreciable at a distance of 15 feet. 

Insulating substance used not to be injured by a temperature of 200° F. 

JEng-ines. 

Engines to work most economically at 100 pounds steam pressure if com- 
pound, and 80 pounds if simple, vacuum being 25 inches ; but they must be 
able to work with pressure 20 pounds above and below these normal 
pressures. 



'28 ELECTRICITY IN THE UNITED STATES NAVY. 



Cylinders to be of hard cast iron cross-heads connecting rods, shafts, 
pistons and valve rods all nuts bolts, etc., to be of best forged steel. 

The design must be such that all parts subject to wear shall be accessible 
for adjustment and repair, especially those parts which by reason of wear 
would affect the alignment of the engine. 

Cylinders must be fitted with relief valves, arranged to work automati- 
cally, in addition to the usual drain cocks. 

All parts must be able to bear without injury the throwing on or off of 
the entire load by quickly making or breaking the external circuit of the 
generator. 

The governor must control the speed automatically, the throttle being 
wide open, within the following limits : 



Variation of Load. 


Variation of Steam Pressure. 


Allowed 

Speed 

Variation. 


Full load to 20% load . 


Constant normal 


Wo 


Constant load .... 


20 lbs. above to 20 lbs. below normal 


3h% 


Full load to no load . 


20 lbs. above to 20 lbs. below normal 


Wo 



If engines have more than one cylinder, the work done in each cyclinder 
must be practically equal at full load and normal pressure. 

Cylinders and valve chests must be covered with suitable non-conducting 
material. Cylinders must be fitted with indicator motions. 

It is very desirable that engines shall be capable of continuous running, 
without the use of lubricants in steam spaces. 

The gross weight of complete sets not to exceed one-third of a pound per 
watt of rated capacity. Generator and engine to be mounted on a common 
bed-plate and direct connected. 

The style of sets installed on the latest ships is a tandem compound 
engine with a six-pole generator, manufactured by the General Electric 
Company. The sizes used are 32 k.w. and 50 k.w. 

The two cylinders are cast together, the L.P. on top, and separated by a 
hollow cast-iron head, which forms the stuffing-box for the L.P. piston rod. 

The engine is entirely inclosed, and is provided with forced oil lubrica- 
tion for the main bearings, crank pin, wrist pin, and cross-head guides. 
Rocker arms, governor and valve stems are provided with automatic grease 
cups. A cylinder lubricator is provided, but is only used a few minutes 
before shutting down, so that the cylinders will be coated with a film of oil 
while standing idle. United States Metallic packing is used. 

32 k.w. size runs at 400 r.p.m. and the 50 k.w. size at 310 r.p.m. 

Tests. 

The 50 k.w. sets of the U.S.S. " Kearsarge" and " Kentucky" gave the 
following average results on tests : 

STEAM CONSUMPTION AT FULL LOAD. 

Steam pressure 100 pounds 

Vacuum 24 inches 

Steam per I.H.P. per hour 21 pounds 

Steam per K.W 35.2 pounds 

Combined efficiency of set 80 % 

REGULATION. 

Normal speed 310 r.p.m. 

Steam constant 100 pounds, full load to 20% load, gives 
variation of ,,,,,,.,., 1.56 % 



SWITCHBOARDS. 729 



Constant full load steam 120 pounds to 80 pounds gives 

variation of 1.5 % 

No load with 120 pounds to full load with 80 pounds 

gives variation of 3.85 % 

Normal voltage 80 volts 

Throw off full load suddenly gives total fluctuation of 9.6 volts 

Throw on full load suddenly gives total fluctuation of 6.9 volts 

HEATING AFTER FOUR HOURS FULL LOAD. 

Armature core surface 21° C rise 

Commutator bars 28 " 

Shunt-field spool surface 11.4 " 

Outboard bearing 7. " 

Armature conductors, by resistance ........ 23.4 " 

Field conductors, by resistance 17.7 " 

Engine has L.P. cylinder 18 inches diameter, H.P. 10i inches diameter, 
with stroke of 8 inches. Clearance in H.P. cylinders is 7£%, in L.P. 
cylinder is 1\%. Weight of complete set is 15,000 pounds. 

The dynamo room is supplied by a special steam pipe which usually is so 
connected that it can take steam direct from any boiler or from the auxil- 
iary steam pipe, it passes into a steam separator from which branches lead 
to each of the generating-sets in the dynamo room. This separator is 
drained by a steam trap which sends the water back to the hot well in the 
main engine room. 

The exhaust pipe from each set joins a common exhaust which connects 
with the auxiliary exhaust service of the ship. If the sets are located 
below the level of the ship's auxiliary exhaust pipe, a separator is placed in 
the common exhaust pipe before it goes up and joins the ship's auxiliary 
exhaust. This separator is drained by a small steam pump, which is 
automatically started and stopped by means of a float in the body of the 
separator, which float starts the pump when the separator is full and stops 
it when empty. 

SWITCHBOABDI. 

The general problem of the design of a generator switchboard for a naval 
vessel is to be able to connect any number of generators to any set of bus- 
bars. There are usually four separate sets of busbars, one for the lighting 
system, one for the power system, and one for the turning-gear of 
each turret. The Ward-Leonard system of motor control being used for 
turning the turrets, it is necessary to use a separate generator for each 
turret. Separate equalizer buses are provided for both the lighting and 
power systems. 

Current is supplied to the different appliances by means of distribution 
switchboards, which have two sets of busbars, one for lighting and one for 
poAver, and are connected directly to the corresponding busbars on the 
main generator board. Feeders run direct from these distribution boards, 
each feeder being provided with a fused switch. Distribution boards are 
sometimes located at various parts of the ship and sometimes made con- 
tinuous with the main board. 

The diagram of generator switchboard and turret turning system on page 
738 shows connections as made on the U. S. S. " Illinois," except there are 
four more generators connected on exactly like the four shown. Each 
generator has a headboard carrying a double-pole circuit breaker, and clips 
for a series field short circuiting shunt used for turret turning. The diagram 
shows generators Nos. 1 and 2 operating in parallel on the power system, 
No. 3 alone on the light system, and No. 4 operating the after turret turning 
motors. It is to be noted that the three generators on the power and light- 
ing systems have the right-hand blades of their triple pole field switches 
closed, giving self-excitation through the field rheostat, while the machine 
for turret turning has the middle blades closed, giving separate field excita- 
tion from the power bus-bars and through the field resistance attached to 
the controller in the turret. 



730 electricity in the united states navy. 
wiiii\c;. 

Specifications. 

The principal requirements of the Navy standard specifications for light 
and power conductors are : — 

All layers of pure Para rubber must contain at least ninety-eight (98) 
per cent of pure Para rubber ; must be of uniform thickness, elastic, tough, 
and free from flaws and holes. 

All layers of vulcanized rubber must contain not less than forty (40) per 
cent nor more than fifty (50) per cent of pure Para rubber ; must be concen- 
tric, continuous, and free from flaws or holes ; must have a smooth surface 
and circular section ; and must be made to a diameter in the finished con- 
ductor that will be in exact conformity with the diameter as tabulated. 

All layers of cotton tape must be filled with a rubber insulating com- 
pound, the tape to be of the width best adapted to the diameter of tbat 
part of the conductor which is intended to bind. The tape must lay one- 
half (J) its width, and be so worked as to insure a smooth surface and 
circular section of that part of the finished conductor which is beneath it. 

All exterior braid must be closely woven ; and all, except silk braid, 
must be thoroughly saturated with an insulating waterproof compound 
which will neither be injuriously affected, nor have any injurious effect on 
the braid, at a temperature of 200° F. (dry heat), or at any stage of test, the 
conductor being sharply bent. Wherever a diameter over vulcanized 
rubber or outsize braid is tabulated or specified, it is intended to secure a 
neat working-fit in a standard rubber gasket of that diameter for the pur- 
pose of insuring water-tightness of the joint, and no departure from such 
tabulated or specified diameter will be permitted. 

All conductors to be of soft annealed pure copper wire. 

No single wire larger than No. 14 B. & S. G. to be used. 

When greater conducting area than that of No. 14 B. & S. G. is required, 
the conductor shall be stranded in a series of 7, 19, 37, 61,91 or 127 wires, as 
may be required ; the strand consisting of one central wire, the remainder 
laid around it concentrically, each layer to be twisted in the opposite di- 
rection from the preceding, and all single wires forming the strand must be 
of the diameter given in the American wire gauge table as adopted by the 
American Institute of Electric Engineers, October, 1893. 

The material and manufacture of the strand must be such that the 
measured conductivity of each single wire forming the strand shall not be 
less than ninety-eight (98) per cent of that of pure copper of the same 
number of circular mills, the measured conductivity of the conductor as a 
whole to be not less than ninety-five (95) per cent of that of pure copper of 
the same number of circular mills. 

Each wire to be thoroughly and evenly tinned. 

All conductors shall be insulated as follows : — 

First. — A layer of pure Para rubber, not less than one sixty-fourth ( B x ? ) 
of an inch in thickness taped or rolled on; if lapped, the tape to lap one- 
half of its width. 

Second. — A. layer of vulcanized rubber, of exact diameter as tabulated. 

Third. — A layer of commercial cotton tape, lapped to about one thirty- 
second (g^) of an inch in thickness. 

Fourth.— A close braid to be made of No. 20 2-ply cotton thread, braided 
with three (3) ends for all conductors under 60,000 circular mills, and of No. 
16 3-ply cotton thread braided with four (4) ends for all conductors of and 
above 60,000 circular mills. The outside diameter over the braid to be in 
exact conformity with that tabulated. 

Tests. Two samples, each 500 feet long, will be selected by the Bureau 
from the coils of wire to be supplied, and must be sent by the Contractors 
to the New York Navy Yard for test. 

(a) Both samples, 'after 24 hours imersion in sea water, must have an 
insulation resistance of not less than 1,000 megohms per nautical mile. 

(6) Test to be at 72° F. 

(c) To be tested by the direct deflection method at a potential of not less 
than 200 volts. 

(d) Both samples will be tested for a conductivity of not less than 96 
per cent of that of pure copper, having a cross-section of tin specified mun- 
per of circular mills, 



LIGHTING-SYSTEM. 731 



(e) Chemical tests will be made to determine the constituents of the 
different layers of the insulation. 

(f) Braid will be tested for water-proof qualities. 

(g) Physical tests will be first made for qualities of strength, toughness, 
dimensions, etc. 

(Ii) The physical and electrical characteristics of the insulation under 
change of temperature will be tested by exposing the finished conductor for 
several hours at a time, alternately, to a temperature of 200° F. (dry heat) 
and the temperature of the atmospere, during a period of three days. 

(i) The tests for characteristics of the insulation will then be repeated 
and must show no practical deterioration on the results of the former 
tests. 

ItKetlious of Insulating- Conductors. 

Three methods of insulating conductors are used. 

1. Conduit ; 2. Molding ; and 3. Porcelain supports 

1. Conduit is the principal method, being used in almost all spaces below 
the protective deck, and wherever wiring is exposed to mechanical injury 
or the weather. Iron-armored insulated conduit is used, except in maga- 
zines, and within 12-feet of the standard compass, where brass is used. 

Conduit passing through water-tight bulkheads is made water-tight by 
means of stuffing-boxes and hemp-packing. Water-tightness is provided 
at the ends of conduit by a stuffing-box and a soft-rubber gasket, through 
which the conductor passes. Long lines of conduit passing through several 
water-tight compartments are provided with gland couplings at proper 
intervals, which divide the run into water-tight sections, thus preventing 
an injury in a flooded compartment from allowing the water to run through 
the conduit into another compartment. These gland couplings are also 
used where conduit passes vertically through decks, and all vertical leads 
are run in conduit. 

2. Wood molding is generally used in living spaces. It consists of a 
backing piece fastened to the iron work of the ship, to which the molding 
proper is secured by screws and covered with a wooden capping-piece. 
Where leads installed in molding pass through water-tight bulkheads, a 
bulkhead stuffing-box is provided for water-tightness. 

3. Porcelain supports are used in dynamo rooms and for the long feeders 
which are run in the wing passages where there is no danger of interference. 
Stuffing-tubes are used where the wires pass through bulkheads, the same 
as with molding. 

Connection Boxes. 

All conductors are branched by being run into standard connection boxes, 
which are usually provided with fuses. Where conduit is used these boxes 
are tapped, to have the conduit screwed into them ; where molding or 
porcelain is used the boxes are provided with stuffing-tubes. The box covers 
are made water-tight with rubber gaskets ; inside the fuses and connection 
strips are mounted on porcelain bases. 

LIGHTOG-SYSTEM. 

YFiring-. 

> The maximum drop allowed on any main is 3 per cent at the farthest 
lamp. Mains are required to be of the same size throughout, and to be of 
1000 circular mills per ampere of normal load. 

fixtures. ' 

Most incandescent lamps are installed in air-tight glass globes of different 
shapes, depending upon position or location. Magazines are lighted by 
"Magazine Light Boxes," which are water-tight metal boxes set into the 
magazines through one of its walls, and provided with a water-tight door 
opening into the adjacent compartment, so that the interior of the box is 
accessible without entering the magazine. The sides of the boxes have 



732 ELECTRICITY IN THE UNITED STATES NAVY. 



glass windows, and each box is fitted with two incandescent lamps, each 
lamp having its own separate fused branch to the main, so that one lamp 
can be used as a spare. 

"Switch Receptacles " containing a snap switch and a plug socket are 
provided for attaching portable lamps. 

Lamps. 

The principal requirements of the standard Navy specifications are : — 

They must be of the best quality and finish, and uniform size ; the bases 
must fit and be interchangeable in the standard socket. 

All leading-in wires and anchors must be fused in the glass ; all anchors 
must be made of metal. 

The filaments must be centered in the bulb, and must not drop when the 
lamps are run in a horizontal position. 

Each lamp must be marked on the inside of the bulb with the date of 
manufacture, and must have its rated candle-power, the voltage necessary 
to give this candle-power, and the name of the manufacturer conspicuously 
labeled on the outside of the bulb. 

The material used for cementing the bases to the bulb must be so treated 
as to insure against danger of short circuiting the lamp when exposed to 
moisture. When porcelain is used all holes must be filled. 

They must be designed for 80 volts, the rated candle-power to be given at 
not less than 78 nor more than 82 volts. No fraction of a volt beyond these 
limits will be permitted. 

The efficiency of all 16 c. p. and 32 c. p. lamps must be not less than 3 &, 
nor more than 4 watts per candle-power, and that of 150 c.p. lamps not less 
than 3 T 2 5 nor more than 3 j 6 s watts per candle-power, the efficiency to be 
measured when the lamps are new. The contractors shall guarantee that 
all lamps supplied will have an average life of at least 600 hours, and that 
the rated candle-power shall not have decreased more than 20 per cent after 
burning for this length of time at the initial potential. 

Before acceptance a test lot will be selected at random from the lot of 
each type of lamp delivered as follows : — 

From lots not exceeding 50 lamps, all lamps. 

From lots exceeding 50 but not exceeding 500, 50 lamps. 

From lots exceeding 500 lamps, 10 per cent of the lot. 
The test lot will be subject to the following tests: — 

(a) For design, dimensions, and construction. 

(b) For vacuum, by trembling of filament and spark. 

(c) For voltage and efficiency when rotating at a speed of 180 revolutions 
per minute. 

(d) For rated candle-power by standard photometer. 

A secondary standard lamp, standardized from the Bureau's standards, 
will be used in the tests. 

A failure of 30 per cent of the test lot to comply with foregoing specifica- 
tions will cause rejection of the lot represented by that test lot. 

Diving-- JLanterns. 

Diving-lanterns consist of a glass cylinder closed at each end with a metal 
cap, having the joint between the glass and metal packed with a soft-rubber 
gasket. On the inside of one of the caps is provided a standard marine 
lamp-socket for 100 candle-power incandescent lamp, to which is connected 
100 feet of twin conductor cable, at the other end of which is connected a 
double pole plug for a standard marine receptacle. 

When first submerged a considerable amount of moisture is deposited in 
the inside, which is drawn out through a small hole made water-tight by a 
screw with a rubber gasket. 

Searchlights. 

The requirements of the standard Navy specifications are : — 
It shall, in general, consist of a fixed pedestal or base, surmounted by a 
turntable carrying a drum. The base shall contain the turning mechanism 
and the electric connections, and be so arranged that it can be bolted 
securely to a deck or platform. 



LIGHTING-SYSTEM. 733 



The turntable to be so designed that it can be revolved in a horizontal 
plane freely and indefinitely in either direction, both regularly and gradu- 
ally by means of a suitable gearing, and rapidly by hand, the gearing being 
thrown out of action. 

The drum to be trunnioned on two arms bolted to the turntable, so as to 
have a free movement in a vertical plane, and to contain the lamp and re- 
flecting mirror. The drum to be rotated on its trunnions, both regularly 
and gradually by means of suitable gearing, and rapidly by hand ; the gear- 
ing being thrown out of action. The axis of the drum to be capable of a 
movement of not less than 70° above and 30° below the horizontal. 

The drum to be thoroughly ventilated and well-balanced ; to be fitted with 
peep sights for observing the arc in two planes, and with hand holes to give 
access to the lamp. It must be so designed that either a Mangin or a para- 
bolic mirror can be used, and means for balancing it with either mirror 
must be provided. 

The mirror to be made of glass of the best quality, free from flaws and 
holes, and having its surface ground to exact dimensions, perfectly smooth 
and highly polished. Its back to be silvered in the most durable manner ; 
the silvering to be unaffected by heat. To be mounted in a separate metal 
frame lined with a non-conducting material, in such a manner as to allow 
for expansion due to heat and to prevent injury to it from concussion. 

The lamp to be of the horizontal carbon type, and designed for both hand 
and automatic feed. The feeding of the carbons must be effected by a posi- 
tive mechanical action, and not by spring or gravitation. It must burn 
quietly and steadily on an 80-volt circuit in series with a regulating rheostat, 
and shall be capable of burning for about six hours without removing the 
carbons. 

The front of the drum to be provided with two glass doors, one composed 
of strips of clear plate glass, and the other of strips of plano-concave glass 
lenses, so designed as to give the beam of light projected from the mirror a 
horizontal divergence of at least 20°. The doors to be interchangeable, and 
to be so arranged that either can be put in place on the drum easily and 
quickly. 

Electrically Controlled Projector. 

To be in all respects similar to the hand controlled, with the addition of 
two shunt motors, each with a train of gears ; one motor for giving the ver- 
tical and the other the horizontal movement of the projector. The motors 
and gears to be contained in the fixed base, and to be well protected from 
moisture and mechanical injury. A means to be provided for quickly 
throwing out or in the motor gears, so that the projector can be operated 
either by hand or by motor, as desired. 

The motors to be operated by means of a compact, light, and water-tight 
controller, which can be located in any desired position away from the pro- 
jector. The design of the controller to be such that the movement of a 
single handle or lever, in the direction it is wished to cause the beam of 
light to move, will cause the current to flow through the proper motor in the 
proper direction to produce such movement. The rapidity of movement of 
the projector to be governed by the extent of the throw of the handle or 
lever. A suitable device to be included whereby the movement of the pro- 
jector can be instantly arrested when so desired. 

All projectors to be finished in a dead-black color throughout, excepting 
the working-parts, Avhicb shall be bright. *- 

The lamps to be designed to produce the best results when taking current 
as follows : 18-inch, 30 to 35 amperes ; 24-inch, 50 to 60 amperes ; 30-inch, 
75 to 90 amperes. 

The 18-incb projector shall project a beam of light of sufficient density to 
render plainly discernible, on a clear, dark night, a light-colored object 10 
by 20 feet in size, at a distance of not less than 4,000 yards ; the 24-inch pro- 
jector, at a distance of not less than 5,000 yards ; and the 30-inch projector, 
at a distance of not less than 6,000 yards. 

The connections for the electrically controlled projectors as manufactured 
by the General Electric Company are shown in the diagram. The fields of 
the two training motors art in series with each other and connected across 
the 80-volt circuit. Both horizontal and vertical training can be simultane- 
ously produced. The controller-handle when released, is brought to the off 



734 ELECTRICITY IX THE UXITED STATES SAVY. 




POWER SYSTEM. 735 



position by springs and short circuits both motor armatures thus stopping 
all movement. 

The horizontal training motor drives through a worm gear, and the verti- 
cal motor through a revolving nut on a vertical screw shaft : all gearing 
can be easily thrown out for quick hand control. 

The highest speeds are 360° in 30 seconds horizontally, and 100° in 60 
seconds vertically. The motors may also be operated at four lower speeds. 

The lamp has a striking magnet in series with the arc and feeding 
magnet in shunt with the arc. When the arc becomes too long, sufficient 
current is forced through the shunt feeding magnet to cause it to make its 
armature vibrate back and forth, and thus move the carbons together 
through a ratchet which turns the feed screws. The point at which tbe 
magnet will begin to feed is adjustable by means of a spring attached to 
armature. The feed screws are so proportioned that the positive and 
negative carbons are each fed together at the same rate that they are con- 
sumed, thus keeping the arc always in the focus of the mirror. Sight 
holes are provided through which the arc may be watched. A permanent 
magnet, fastened to the inside of the projector and surrounding the arc on 
all sides but the top, causes the arc to burn steadily near the upper edge of 
the carbons and in focus with the mirror. 

The rheostat is located near the switchboard, and after being once set 
for proper working does not need to be again changed. Double-pole circuit 
breakers are used at the switchboards for switches. 



SIGSAX EIGHTS. 
Ardois Sig-nals. 

The Ardois signals consist of four double lanterns, each containing a red 
and a white light, which are hung from the top of the mast, one under the 
other and several feet apart. By means of a special controller any number 
of lanterns may have either their red or white lamps ligbted, thus producing 
combinations by wbich any code can be signaled. The lamps used are 
clear, and the color is produced by having the upper lens which forms the 
body of the lantern colored red ; the lower lens is clear. 

The controller consists of eight semi-circular plates, with pieces of hard 
rubber set in the inner edges where needed, and a rotating center stud 
with eight plunger contacts rubbing on the edges of the plates. By suita- 
bly placing tbe pieces of hard rubber for any given position of the 
contacts, any desired combination of lights can be produced. 

The operation consists in moving the arm carrying the contacts to the 
position desired (as shown by a pointer on an indicating dial; and closing 
the operating switch, when the proper lamps will light. 

Truck lig-hts. 

The truck lights are lanterns of construction similar to the Ardois 
lanterns, mounted, one on the top of both the fore and main masts. By 
means of a special controller the red or white light in either lantern can be 
lighted. 

POW-EI& SYSTEM. 

Motors are kept entirely separate from lights by the use of different 
bus-bars on the generator switchboard and distribution boards. Each 
motor or group of motors is supplied by its own feeder running from the 
distribution board, where it has its own fused switch. A maximum drop of 
5 per cent is allowed. 

JB»rincipal Mequirements of Specifications for Iflotors. 

Motors to be wound for 80 volts direct current. 

Sizes above 4 H. P. to be multipolar ; 4 H. P. and below may be bipolar. 
Armatures to be of iron-clad type, and coils preferably to be separately 
wound and easily removable. 



736 



ELECTRICITY IN THE UNITED STATES NAVY. 



Band wires to be of non-magnetic material, and not more than three to 
be used under poles. 

Commutator segments to be of pure copper, insulated with mica of such 
quality that it will wear evenly with the copper. 

Carbon brushes to be used carrying not more than 30 amperes per square 
Inch at full load. 







PILOT LAMP 

Fig. 2. Diagram of Ardois Signal Set. 



POWER SYSTEM. 737 



No sparking to occur up to full load with no shifting of the brushes. 

To prevent deterioration from rust and corrosion, such parts as bolts, 
nuts, screws, pins, and fittings of a light character, which if rusted or 
corroded would injure the operation, strength, ease of adjustment or taking 
apart, or appearance, are to be made of tobin bronze, or similar metal, and 
not of iron or steel. 

No insulating substances to be used that can be injured by a temperature 
of 94° 0. Test for dielectric strength to be made with a pressure of 1500 
volts alternating for 60 seconds, using a transformer and generator of at 
least 5 k. w. capacity. 

Allowed temperature rises above surrounding air are : — 

Continuous running motors, open type, windings 35° C, commutator 40° 
C, after eight hour full-load run. 

Same as above, but closed type, 50° C, for both winding and com- 
mutator. 

Intermittent running motors have special requirements depending upon 
use ; but nearly all require 45° C. for all parts after one hour at constant 
full-load. 

Bearings of all motors 40° C. 

Lubrication of continuous running motors is by oil rings or sight feed 
cups, the intermittent running motors by grease pockets. 

Every motor to be protected by an automatic circuit-breaking device, 
capable of being set to 50 % above the normal full load. 

Turret-Turning" (<fear. 

The motors are controlled by the Ward-Leonard system, the principle of 
operation of which is illustrated by the elementary diagram on the diagram 
of generator switchboard and turret-turning system, page 738. 

The motors are shunt wound, and have the fields constantly separately 
excited from the bus-bars of the ship's power system. A separate generator 
is required which cannot be used for any other purpose when used with the 
turret. The generator is also separately excited from the power bus-bars ; 
but a variable rheostat, located in the turret, is connected in the shunt- 
field circuit. The brushes of the motor are directly connected to the 
brushes of the generator, and the generator is kept running at constant 
speed by its driving-engine. It is now evident that by varying the rheostat 
in the turret, the field excitation, and consequently the voltage produced 
by the generator, will be varied ; and any variation in the voltage of the 
generator will produce a corresponding variation in the speed of the motor, 
which has a constant field from separate excitation. The direction of rota- 
tion of the motor is reversed by reversing the leads to the armature. The 
actual connections for the application of the above principles are shown in 
the main part of the diagram. Generator No. 4 is shown connected for 
operating the after-turret. 

Closing the after-turret field switch and the center blades of the generator 
field switch, separately excites the fields of the motors and generator from 
the power bus-bars. The regular field rheostat of the generator is entirely 
disconnected, and a rheostat located in the turret and operated by the tur- 
ret turning controller is used instead. 

Closing the positive and negative single-pole switches on the after-turret 
bus-bars connects the generator armature to the motor armatures, through 
a circuit breaker, the reversing contacts of the controller, and separate 
armature switches for each of the two motors, which are operated in 
parallel. 

The controller has one shaft, at the top of which are located the con- 
nections for the generator field rheostat, so arranged that as the controller 
is turned either way from the off position the rheostat is gradually cut out ; 
below are located the reversing contacts, which reverse the connections 
between the generator armature and the motor armatures ; these contacts 
are so arranged that at the off position the motor armatures are entirely 
disconnected from the generator, and are short-circuited through a low 
resistance called the " Brake resistance." The effect of this brake resist- 
ance is to bring the turret to a quick stop when the controller is brought 
to the off position, as the motor armatures revolving in a separately excited 
field generate a large current, which passes through the braking resist- 
ance, and thus absorbs the kinetic energy of the turret, giving a quick and 



'38 ELECTRICITY IN THE UNITED STATES NAVY. 




POWER SYSTEM. 739 

smooth stop. In parallel with each of the large main ringers of the re- 
versing contacts is a small auxiliary ringer and an auxiliary resistance 
connected to it. This auxiliary finger makes contact a little before and 
breaks it a little after the main finger, and thus reduces the sparking. 
The controller is also provided with a magnetic blow-out for reducing 
sparking at contacts. 

When used on this system for operating a turret the generator has its 
series coil short circuited by a very low resistance shunt, so that it has very 
little effect on the field excitation, but this resistance is so proportioned 
that enough of the total current generated by the generator will pass 
through the series coil to give a quick and positive start of the turret ; be- 
cause if the series coil is absolutely short circuited, and only the separately 
excited shunt coil used, the time required for the field to build up is suffi- 
cient to make the starting of the turret very sluggish and irregular, and pre- 
vents very fine training from being obtained. 

On the U.S.S. " Kearsarge " and " Kentucky," two 50 H. P. motors of 400 
r.p.m. are used to turn each double turret, which weighs 710 tons and is 
mounted on 32-tianged conical rollers, 15^-inches diameter, running on a 
track 21 feet in diameter. Each motor drives through a worm and wheel, 
connected to a spur pinion meshing into a stationary circular rack. The 
motors are geared together by a cross shaft. Friction clutches are inserted 
in the transmission gearing to prevent sudden stops, firing the guns, or im- 
pact of shot, from breaking the gearing. Full speed of the turret is at the 
rate of one revolution per minute. The controller is provided with a me- 
chanical automatic stop which brings it to the off position when the turret 
reaches the limit of its train at either side. 

The following results were obtained on test of the four turrets of the two 
ships. The friction varied considerably for different turrets. 

Forward turret of the " Kearsarge " gave : — 

Turning at constant full speed, 

Input of motors 22 E.H.P. 

Output of motors 13 H.P. 

Maximum when accelerating at rate of attaining 
full speed in 10 seconds, 

Input of motors 44.5 E.H.P. 

Output of motors . 36.3 H.P. 

This was the easiest running of the four turrets. 
The hardest running gave, 
Turning at constant full speed, 

Imput of motors 41 E.H.P. 

The motors are seen to be greatly over-powered for the work, this to 
allow for overcoming any deformation of track, rollers, etc., which might 
occur during action. 

Fineness of train obtained : — 

The turrets were easily started and stopped with a resulting movement of 
10 seconds of arc, which equals a movement of about 2 inches at 1,000 yards 
range. 

This is a movement much smaller than the visual angle covered by the 
cross hair of the sighting telescope, so that the fineness of train is much 
greater than that of sighting. 

A turret was turned through its extreme train from one side to the other 
48 times in one hour, with a stop being made at each beam position during 
each trip. 

The motors used were entirely inclosed and weighed 5,700 pounds. 

Iioading- and Training- drear for Guns. 

Guns of 12-inch and over are elevated and rammed by power, smaller guns 
have hand gear. 

The elevating gear for 12-inch and 13-inch guns consists of a 1\ H.P., 80-volt, 
300 r.p.m. series motor, geared to a revolving screw which raises or lowers a 
nut crosshead from which connecting rods go to the gun. 

Ordinary rheostatic control is used with no braking appliance. To train a 
13-inch gun at the rate of 30° per minute, an armature input of from 1.5 to 



740 ELECTRICITY IN THE UNITED STATES NAVY. 



3 E.H.P. is required, depending upon the condition of the load and whether 
elevating or depressing. The motors used are entirely inclosed and iveigh 
550 pounds. 

Hammers consist of a telescopic tube worked through spur and chain- 
gearing by a 5 H.P., 80-volt, 775 r.p.m. series motor. A friction slip clutch 
is inserted in the gearing to prevent damage when the shell seats itself in 
the breach. Ordinary rheostatic control is used. 

When ramming a shell but little power is required, as the shell slides 
along the breech, but as it is being forced to its seat at the end of the breech 
chamber a sudden rush of current of from two to three times the full-load 
current of the motor is produced. 

The motors used are similar to the elevating motors, except wound for 
higher speed. 

AUHWXWITI©^ HOISTS. 

Power ammunition hoists are of two kinds ; first, those in which a car 
or cage is hoisted up and down by a line wound on a drum on the motor 
counter-shaft ; and second, those in which the motor runs an endless chain 
provided with toes or buckets on which the ammunition is placed and con- 
veyed up through a trunk. 

Hoists for 12-inch and 13-inch Ammunition. 

These hoists are of the first kind. The motor frame is provided with 
bearings for a counter-shaft, geared by a spur-gear and pinion to the arma- 
ture shaft; on the counter-shaft is mounted a grooved drum for the hoisting- 
cable. 

On the armature shaft is mounted a solenoid hand-brake. The cores of 
the solenoid are weighted and attached to the brake-setting lever so that 
when free their weight is sufficient to hold the loaded car from falling ; 
when the solenoids are energized the cores are drawn up and the brake re- 
leased. 

The controller is constructed so that on the off position the solenoids are 
not energized and the brake is set ; but at all other points, both hoisting and 
lowering, the solenoids are energized and the brake released. 

Shunt motors are used, and the control for hoisting is ordinary rheostatic ; 
the resistance being put in series with the armature and gradually cut out, 
the field is always constantly excited as soon as the feeder-switch is closed. 
For lowering, the entire rheostat is thrown directly across the line, one 
armature lead connecting to one side of the line and the other lead gradu- 
ally moved (as the motor is brought to full speed) from the condition of a 
short-circuited armature at the off position to direct connection to the other 
side of the line at the full on position ; in all intermediate positions the 
armature is in shunt with a part of the rheostat. The object of this is to 
cause the armature to take current from the line and run as a motor when 
lowering a light load which will not overhaul, but to run as a generator and 
send current through the rheostat if the load is very heavy and overhauls 
the motor and gearing. In either case the speed will depend upon the 
amount of the rheostat that is in shunt across the armature. The off posi- 
tion of the controller short-circuits the armature, and since the fields are 
always excited, this gives a quick stop and also holds the load. 

The 13-inch hoists of the U.S. S. "Kearsarge" and "Kentucky" used 20 
H.P. motors running at 350 r.p.m., with a gearing ratio of 6.43 from arma- 
ture to counter-shaft. 

The load was, empty car 1,846 pounds, and full charge 1,628 pounds, or a 
total of 3,474 pounds. 

The following average results were obtained when testing at hoisting full 
charge : — 

Hoisting-speed, feet per minute 180 

Mechanical H.P. in load 18.96 

Input of motor, E.H.P . 28.5 

Total efficiency 66.6% 

Motors were designed to be suspended under the turret, were entirely 
inclosed, and weighed 3,000 pounds complete with brake. 



AMMUNITION HOISTS 



741 




Hoists for S-inch Ammunition. 

Hoists for smaller ammunition are made and controlled in a similar 
manner as the above, except the solenoid brakes are replaced with an ordi- 
nary band-brake, operated by a foot or hand lever. 

The 8-inch hoists used a 6 H.P.,375 r.p.m. shunt motor to hoist a total load 
of 910 pounds at 163 feet per minute. 

Tests gave average results of, — 

Mechanical H.P. in load 4.5 

Input of motor, E.H.P 7.4 

Total efficiency 60.8% 



742 ELECTRICITY IN THE UNITED STATES NAVY. 



JBmiless Chain Ammunition Hoists. 

These hoists run continuously, the ammunition being fed in as desired. 
The motor is geared to the chain sprockets by spur gearing, is shunt wound, 
and is started arid stopped by a controlling panel, wliich is provided with no 
voltage and overload release, a held rheostat for varying the speed of the 
motor, and a reversing-switch. 

A solenoid brake, similar to the one above described for the 13-inch 
hoist, is mounted on the armature shaft, and is set when the starting-arm 
is in the off position, but has its coils energized and is released when the 
arm makes the first contact in starting. At the full on position, part of the 
starting rheostat is in series with the brake, thus cutting down tne current 
consumed by it. This does not affect the reliability of the brake, since the 
current required to hold up the cores is much less than that required to 
first start them, and at the start the full-line voltage is on the coils. 

To lower ammunition the reversing-switch is thrown down, which re- 
verses the connections to the motor armature, and puts in the armature 
circuit a safety switch. This safety switch is attached to the lever which 
operates the catch pawls in the hoist trunk. These pawls will allow am- 
munition to go up, but will catch and prevent it from going down, and are 
used to keep the ammunition from falling in case any part of the hoist 
should be shot away. When the paAvl lever is thrown down it throws the 
pawls out of action, and allows ammunition to be lowered by reversing the 
motor ; it also closes the safety switch which completes the armature cir- 
cuit for the lowering position of the reversing-switch. 

This style of hoist is used for all kinds of ammunition up to and includ- 
ing 6-inch. Packages are so made that they weigh about 100 pounds each. 
Motors rated at 3| H.P., continuous running, with speed variation of 360 to 
475 r.p.m. are used ; power required varies greatly with kind and style of 
hoist. Motors are entirely inclosed and weigh 980 pounds. 



BOAT €RAI¥E§. 

For handling steam cutters and other boats a revolving crane having the 
general shape of a davit is used ; it extends down to the protective deck, 
and has a steady bearing at each deck passed through, and the weight is 
carried by a roller thrust bearing. The operating machinery is carried on 
a circular platform fastened to the crane. 

The cranes for the U.S.S. "Kearsarge" and "Kentucky" have two 
motions ; namely, rotating the entire crane, and raising or lowering the 
hook. One motor only is used for both motions, clutches and gearing being 
used to produce either at will. Two counter-shafts are driven by the 
motor, each having a worm at the end, one driving a worm wheel on the 
hoisting-drum and the other a worm wheel on the shaft of the rotating 
pinion. Each of the countei'-shaf ts contains a friction clutch, so that it can 
be disconnected from its worm at will. 

A band-brake is provided on the rotating-worm to hold the crane from 
rotating. A strap brake is provided on the hoisting-drum, which consists 
of a wrought-iron strap, one end of which is permanently fastened to the 
platform, wound three times around the hoisting-drum and the free end 
attached to a weighted lever which pulls it taut. This strap is wound 
around the drum in the direction it turns when lowering, so that any 
motion in this direction causes the friction to make the strap bind tighter 
and hold the drum from turning ; but rotation of the drum in the hoisting 
direction causes the friction to make the strap loosen up and allow the drum 
to continue rotating. Thus the brake automaticallv holds the load from 
over-hauling the drum when the motor is disconnected. For lowering, the 
brake has its free end raised by a hand lever, thus loosening it, and allow- 
ing the drum to turn in the lowering direction. 

The motor is shunt wound with field constantly excited as soon as the 
feeder switch is closed at the distribution board, 

The controller cylinder gives ordinary rheostatic control with resistance 
in series with the armature, but there is a commutating switch which when 
closed gives the same kind of control as used for lowering with the 13-inch 
ammunition hoist described above ; this control is used for lowering and 



BOAT CRANES. 



743 



rotating, since it gives a smoother stop, and the rheostatic control is used 
for hoisting. The oil" position of the controller short circuits the arma- 
ture, giving a quick and positive stop. 

A 40-foot steam cutter is the largest boat handled, and weighs complete 
16,000 pounds. 




_/ \ BLOWOUT 

I Oh COIL 



COLLECTOR RINGS 
ON CRANE 



COMMUTATING 
SWITCH 



M 



X 



Fig. 5. Diagrams of Connections for Boat Crane Motors 



The weight of the complete crane is 54,000 pounds. 

Motor is 50 H.P., 400 r.p.m., is entirely inclosed and water-tight, and 
weighs 5,890 pounds. Current is supplied through collector rings mounted 
on the cranes. The controller is water-tight, and the circuit breaker is 



744 ELECTRICITY IN THE UNITED STATES NAVY. 



mounted in a water-tight iron box ; all were tested for water-tightness by 
playing a stream of salt water on them from the fire-hose. 
The following results were obtained on test : — 



Load of 16,000 pounds 

Hoisting-speed, feet per minute ... 25 

Mechanical H.P. in load 13.64 H.P. 

Input of motor to hoist . ..... 30.6 E.H.P. 

Total efficiency 44.5 % 

Rotating speed 1 r.p.m. 

Imput of motor to rotate 14.8 E.H.P. 

EMPTY HOOK. 

Input of motor to hoist 7.3 E.H.P. 

Input of motor to rotate 8.9 E.H.P. 

It is seen that the motor is very much overpowered for the ordinary work 
required, but this is done to have a large margin to be able to handle boats 
in rough weather when the ship is rolling. Especial strain will be pro- 
duced when rotating a boat in when the ship is heeled over, and also from 
the inertia effect of rolling. 



DECK WINCHES. 

The electric deck winches of the U.S.S. "Kearsarge" and "Kentucky" 
consist of a series motor geared through a system of spur-gearing to the 
shaft carrying the winch heads. 

The control is ordinary rheostatic, with the controller suspended horizon- 
tally from the deck underneath the winch and operated by a vertical shaft 
and a pair of bevel gears. Braking is accomplished by a foot lever, operat- 
ing a brake-band. Eor ordinary working the controller is turned to the 
full speed and the winch allowed to run continuously, the load being con- 
trolled by taking several turns of the hoisting-rope around the winch 
head. The maximum load can be very nicely controlled in this manner. 

The capacity of the winches is 2,200 pounds at 300 feet per minute ; and 
two winches are provided with a compound gear which can be thrown in to 
give a speed of 50 feet per minute with a corresponding pull of 13,000 
pounds. The motors are 25 H.P., with a full-load speed of 320 r.p.m., but 
when the winch is allowed to run without load the speed of the motor 
increases to about 900 r.p.m. 

When hoisting 2,200 pounds at 300 feet per minute, the average test 
results were : — 

Mechanical H.P. in load 20 H.P. 

Input of motor 34.3 E.H.P. 

Total efficiency ......... 5S.4 % 

Motors are entirely inclosed and water-tight, and were tested for water- 
tightness by playing a stream of salt water from the fire-hose on them 
without any water entering. 



vuarTiiiATiour jfahts. 

Nearly all compartments of a ship have artificial ventilation by power 
fans ; both exhaust and pressure systems being employed. Both steam and 
electric drive is used, steam being used almost entirely for forced draught 
in the boiler rooms, while electric predominates for all other places. 

Shunt motors are used, started, and stopped by a controlling panel having 
"no voltage" and "overload" release. Speed variation is obtained by a 
field rheostat. 

The following table gives results of tests on different sizes and styles of 
fans when run at full load and speed : 



STEERING-GEAR. 



745 



Fan. 


cS 

-a 

as 


o 
"8.3 


ft 

"3 


? 

B 

DO - 


Us 


P3 

a . 


COfcJ o 
02 ^ 


Steel plate . . 


Blower 


50" 


500 


If 


12500 


ll.l 


300 


No. 6 Monogram, 
Sturtevant . 


Ex- 
hauster 


27i" 


1030 


li 


2580 


2.7 


810 


No. 5 Monogram, 
Sturtevant . 


Ex- 
hauster 


24" 


1220 


i* 


1460 


1.43 


910 


No. 3 Monogram, 
Sturtevant . 


Ex- 
hauster 


141" 


1650 


li 


835 


.77 


1196 



STEE«IA<;.(iEiH 

Electrical steering-gears are not at present used in the United States 
Navy, hut are somewhat used in foreign navies. One method used is 
shown in the diagram of connections in which M is a shunt motor oper- 
ated from the ship's mains and running continuously at constant speed ; 
its shaft is directly coupled to G, a shunt generator, the two forming a 

SHIPS MAINS 




Fig. 6. Diagram of Steering-Gear. 



motor generator set and located at any desired place, most conveniently in 
the dynamo room. P is a shunt motor geared by suitable gearing to the 
rudder post, and has its field constantly excited from the ship's mains, its 
brushes are directly connected to the brushes of the constantly running 
generator G. R and R' are two equal and symmetrical rheostats, the con- 
tact arm of R being attached to the rudder post or any part of its gearing 
which has a similar rotation, and the contact arm R' being attached by 
suitable gearing to the steering-wheel. The ends of the field of G are con- 
nected to these two contact arms, and the two rheostats are connected 
across the ship's mains. 

It is now seen that the two rheostats and the field of G form a Wheat- 
stone's bridge, the parts of the rheostat on each side of the contact arms 
being the four resistances, the field of G taking the place of the galvanom- 
eter and the line being the battery. This bridge is in balance, and no 



'46 



ELECTRICITY IN THE UNITED STATES NAVY. 



current will flow through the field of G Avhenever the two rheostant arms 
occupy similar positions on their respective rheostats ; but if they do not 
occupy similar positions, then the bridge will be out of balance and current 
will flow through the field of G. 

The operation is as follows : Starting with everything central as shown 
in the diagram, if the steering-wheel is turned, moving the arm of R' a 
certain distance, the balance will be disturbed and current will flow through 
the field of G, causing it to generate an E.M.F. and start the motor P, which 
will continue to run until the arm of R has been moved a distance equal to 
the original movement made by the arm of R', when the balance will be 
restored, no current will flow through the field of G, which will then 
develop no E.M.F., and the motor P will consequently stop. The gearing 
between P and the contact arm of R is so arranged "hat the movement of 
the arm will be in the proper direction to restore the balance. The direction 
of current flow in the field of G, and consequently the polarity of G and 
direction of rotation of P, will depend upon the direction of movement of 
the arm of R'. It is thus seen that the arm of R is given an exact copying 
motion of the arm of R', both for distance moved and direction of rotation. 

Instead of actually turning the rudder, the motor P can be made, if 
desired, to only operate the valve of a steam-steering engine ; when this is 
done the device is called a " Telemotor." 

Another method (which has only been applied for use as a telemotor) has 
the first movement of the steering-wheel connect the operating motor 
directly to the ship's mains, and the motion of the motor causes a step by 
step mechanism to disconnect it when it has moved the engine valve a 
distance proportional to the original movement of the steering-wheel. Both 
connection and disconnection of the operating motor are made by a switch 
at the steering-wheel, the interrupter of the step-by-step mechanism is at 
the operating motor and the mechanism itself at the steering-wheel. The 
mechanical arrangements are quite complicated. 

Several ships of the Russian Navy have been fitted with direct acting 
steering-gears by the Electro-Dynamic Company, of Philadelphia, Pa., 
and work on the above first described bridge principle, with the addition 
of a small exciter for the generator mounted on the generator shaft, and 
the field of this exciter is connected with the bridge rheostats, instead of 
the main generator field itself. The motor of the motor-generator is rated 
at 70 H.P., the generator at 500 amperes and 100 volts, and the rudder 
motor at 50 H.P. ; all being easily capable of standing 50% overloads for 
short periods of time. The motor-generator runs at 650 r.p.m. and weighs 
11,000 pounds ; the rudder motor runs at 400 r.p.m. and weighs 5,500 pounds ; 
the accessory appliances weigh 1,500 pounds, making a total weight of 
18,000 pounds. 

Tests made on the Russian Cruiser " Variag" took 150 H.P. to move the 
rudder from hard-a-port to hard-a-starboard in 20 seconds, while going at a 
speed of 23 knots an hour. For ordinary steering at about 19 knots, readings 
taken every time the rudder was moved gave the following results : — 



Amperes. 


Volts. 


K.W. 


250 


4 


1. 


250 


10 


2,5 


150 


14 


2.1 


180 


30 


5.4 


200 


40 


8. 


100 


50 


5. 


100 


55 


5.5 


50 


5 


.25 


50 


25 


1.25 


60 


40 


2. 


100 


22 


2.2 


100 


25 


2.5 


50 


15 


.75 


200 


26 


5.2 


100 


18 


1.8 


100 


20 


o 



WATER-TIGHT DOOR GEAR. 747 



Readings were taken for every movement occurring for a period of \ hour, 
rudder was never moved more than 15 degrees. 

WATER-TIGHT DOOR GEAR. 

An arrangement for electrically operating sliding water-tight bulk-head 
doors has been experimentally tried and has given good results. The sliding 
door is provided with a rack and pinion, the shaft of the pinion being con- 
nected through a worm gear with a 1 H.P. motor, compound wound, of 
the sbort shunt type, the shunt coils being relatively weak. The circuits 
are so arranged that for raising the door, only the series coils are in circuit, 
giving quick and easy starting, while for closing the door where it may be 
necessary to cut through coal, the shunt and series coils are both in circuit. 

The door can be opened or closed by a switch having a handle on both 
sides of the bulkhead. A limit switch is provided, which is opened by a 
bell crank when the door reaches either of its extreme positions. An 
emergency control is also provided by means of which all doors in the ship 
can be closed at the same time from any desired place, such as the conning- 
tower. 

The diagram on the next page shows the connections for the control of 
one door, and the parts are as follows : — 

S and S' are two separate solenoids having attached to their cores, by 
insulating washers, cross contact arms, which make and break contact 
across the contact clips 1, 2,3,4, etc. When a solenoid is energized it draws 
up its core and the arms make contact across the two upper pairs of clips, 
and when it is not energized the weight of the core will cause it to drop and 
the arms make contact across the two lower pairs of clips. 

L and 1/ are the limit switches. 1/ is opened when the door reaches its 
upper limit of travel, but is closed at all other positions. L opens its left 
hand pair of contacts and closes its right-hand pair of contacts at the 
extreme down position, but at all other positions it is closed at the left 
and open at the right. The left-hand contacts form the limit switch, the 
right-hand ones being used for signal connections described later 

O is the local control switch at the door, and can be operated from either 
side of the bulkhead. It is provided with a spring which keeps it on the 
middle point when released. 

E is the emergency control switch, and is located at any desired point on 
the ship. I 

D is a signal lamp located near E at the emergency station. 

A and B are the ship's mains. 

The operation is as follows : — . . ^ ■ . . . 

To Open Door. — Move local control switch C to its right-nand con- 
tact which will energize solenoid S', the circuit being from main A through 
arm' of C, through I/, through S', across contacts 2, to main B. This will 
raise the core of S' and the arms will connect across contacts 5 and 7, and 
the motor will be connected to the mains as a series motor, the shunt coils 
being idle. The circuit is from main A through contacts 5, through the 
armature, across contact 7, through the series field to main B, and the 
motor will run in the raising direction until the switch C is released, or 
until the door reaches its upper limit and opens the limit switch I/, which 
will open the solenoid circuit and allow the core to fall, thus cutting off the 

To close Door.- Move switch C to its left-hand contact, which will 
energize solenoid S, the circuit being from main A through arm of C, 
through L, across contacts 8. through series field coil to main B. This will 
raise the core of S and connect across contacts 1 and 3, and the motor will 
be connected to the mains with both the shunt and series coils in use. Ihe 
circuit is from main A through contacts 1, through armature through con- 
tacts 3, through series coil to main B ; and for the shunt field is from mam 
A through shunt field to side of armature which connects to the series coil 
and through it to main B, giving a short shunt connection. This will cause 
the motor tc run in the lowering direction until C is released and the limit 

Whenever the motor is stopped both solenoids are released as drawn in the 
diagram, and the armature is short circuited through its series field, thus 
giving an electrical braking effect which absorbs the kinetic energy of the 



748 ELECTRICITY IX THE UNITED STATES NAVY. 



A 



E 





i-o 1 



-5^ i ^l-5r^s , 



-STttIS-J— STfnS— 



-Q ; 



•iff 



r 



i ^- l ^i 



Q-Etf] 



7 fTl 



v£M^ 




Fig. 7. 



Diagram of Connections for Electric Control of Watertight 
Sliding Doors. 



INTERIOR COMMUNICATION SYSTEM. 749 

armature and other moving parts, and gives a smooth and quick stop. The 
circuit is from right brush, through contacts 6 and 2, through series field, 
through contacts 8 and 4 to left brush. 

The door can be closed from the distant emergency station by closing the 
switch E, which gives the same result as moving switch C to its left-hand 
point, since closing E connects the pivot of C to the left point, the circuit 
being through the center point on which C normally rests. It is thus seen 
that the closing ot E does not affect the action of C, since as soon as C is 
moved from its center point E is cut out. 

If the door is closed at the emergency station by means of E, the lamp T> 
will light up as soon as the door is completely closed, for the closing of the 
door operates the lower limit switch L and closes its right-hand contacts. 
The circuit is from main B through lamp, through right sontacts of L, 
through E, through C, to main A. 

If desired all doors in the ship can be closed by one emergency switch, by 
having that switch operate a solenoid having a pair of contacts for each 
door, or the doors may be divided into sections, each section having a sepa- 
rate emergency switch and solenoid. 

Since the motor takes its maximum current just at the instant of final 
closing of the door, the speed of the different motors on any one section is 
so adjusted that the doors will reach the end of their travel one after the 
other with a small time interval between each, thus preventing the sudden 
drain of current from the ship's generators that would occur if all shut ex- 
actly at the same instant.. One-third k.w. of generator capacity is allowed 
per door for a system. This system is made by the " Long Arm " System 
Company, Cleveland, O. 

The following results were obtained on test: — 

Amperes. Volts. 

To start the door down 13| 115 

Steadying while closing at 3J 113 

To start the door up 22 115 

Steadying while opening at 11 113 

With fine bituminous coal heaped against the back of the door to within 
six inches of the top : — 

Amperes. Volts. 

To start the door up 24J 115 

Steadying while opening at 11 113 

On opening the door wide the coal ran through the doorway, and the door 

was then closed through this coal lying eleven inches deep on the sill : — 

Amperes. Volts. 

To start the door down 14 115 

13.5 115 
Cutting through coal and within an inch of seat- 
ing, steadied at 3 113 

3 113 
While driving loose coal through the hollow sill 

the ammeter jumped to 52 115 

49 113 

INTERIOR COMMUNICATION SYSTEM. 

The interior communication system of a ship consists of, as the name 
implies, the appliances for transmitting signals of all kinds from one part 
of the ship to another. 

Order and Position Indicators. 

Many devices have been tried for the electrical transmission of pre- 
arranged orders, or the position of a moving body, such as a rudder-head ; 
but the most successful and the one generally installed consists at the re- 
ceiving end of a number of small incandescent lamps, each mounted in a 
small separate light tight cel.l with a glass front, and the whole inclosed in 
a suitable case. On the glass front of each light cell is marked an order or 
number, or whatever particular information the particular device is to in- 
dicate. This receiver is connected to the transmitter by a cable having a 



750 ELECTRICITY IN THE UNITED STATES NAVY. 



separate wire for each lamp, and one wire for a common return. The trans- 
mitter consists of a switching device, by means of which any lamp or lamps 
in the receiver may be lighted, the current being taken from the lighting 
mains. As many receivers as desired can be operated from one transmitter, 
the receivers being connected in parallel. 

Helm Angle Indicator. 

When the above-described device is used to indicate in different parts of I 
the ship the angle that the helm is turned, the transmitter switch consists 
of an arm, as shown in diagram No. 8 on the next page, fastened to the 
rudder stock, and moving over a series of contact pieces arranged in an arc 
m the same manner as an ordinary field rheostat. Each of the contact 
pieces is connected, through one wire of an interior communication table, to 
one side of one of the receiver lamps, which lamp has marked on its front 
the number of degrees that the given contact is situated from the center-line 
of the ship ; the other side of the lamp is connected to the common return 
wire, which goes to the source of current and then to the contact arm. 
As the rudder turns, the contact arm makes connection with the different 
contact pieces, and as it touches each piece the corresponding lamp in the 
receiver lights up and indicates its position within the limits shown ; when 
it is just midway between any two pieces it will touch both and light both 
corresponding lamps, which doubles the closeness with which the position 
is indicated. 

As many receivers can be connected on as desired, all being operated in 
parallel. 

.Engine Telegraphs. 

When used for engine order telegraphs the contact arm is mounted in a 
metal case and operated by a hand lever of the same construction as the 
hand lever of an ordinary mechanical ship's engine telegraph. The case 
contains indicator lamps in parallel with the lamps of the receiver at the 
engine-room, so that the operator on the bridge has visual evidence of the 
order sent. A small magnetto is geared to the transmitter handle, and rings 
a bell at the receiver whenever the handle is moved, thus calling attention 
to the change of order. 

Battle Order Indicators. 

The receiving indicators are of the same construction as above described 
for the Helm Indicators, but the transmitter consists of single-pole snap 
switches, connected up exactly like the lamps of the indicator, so that by 
turning the proper switches any desired number of lamps can be lighted, 
and of course any desired order can be marked in front of any lamp. Sev- 
eral indicators, located in different parts of the ship, are usually worked by 
each transmitter, all being connected in parallel. 

The case which contains the. transmitter switches also contains an indica- 
tor, thus always showing what orders are being indicated on the system. 

Range Indicators. 

Range indicators are exactly like the Battle Order Indicators, except that 
instead of having different orders marked before each lamp, a number rep- 
resenting the range in yards is marked. 

A range indicator and a battle-order indicator are usually mounted to- 
gether at desired stations, thus showing what kind of firing is to be done, 
and at what range. 

Revolution Indicators. 

To show on the bridge the direction and speed of rotation of the engines, 
several appliances have been devised. The one most generally used is shown 
in Fig. 9, and consists at the transmitter of a small gear E, mounted eccen- 
trically upon the propeller shaft S, and meshing with a pinion P, which is 
carried on the lower end of an arm A. The arm A is slotted and mounted 
on a pivot as shown, and when S is rotating, A will be turned to one side or 
the other, depending upon the direction of rotation of S, until it hits on the 
stop B, and will then remain against the stop and reciprocate up and down 
from the eccentric action of E ; on each up movement it will make contact 
with clip C or C', depending upon which side it is turned. 



INTERIOR COMMUNICATION SYSTEM. 



'51 




o 

z 
o 


3 


H 


<c 






o 


&D 


z 


< 



m*h 



% 



CONTACT ARM FASTENED TO RUDDER POST 



The receiver consists of two pivoted pointers, connected as shown to two 
electro-magnets and marked "Astern " and " Ahead." 

From the connections shown, it is seen that at each rotation of the pro- 
peller shaft the pointer corresponding to the direction of rotation will make 
a movement, and at the same time the magnet armature will make a plainly 
audible click, thus indicating both visually and audibly the rotation. The 
other pointer corresponding to the direction in the opposite rotation will 



i 



752 



ELECTRICITY IN THE UNITED STATES NAVY. 



remain still. For twin screws a separate transmitter and receiver is in- 
stalled for each. 

A separate mechanical indicator is also usually installed, consisting of a 
small shaft geared to the propeller shaft, and running to the bridge (angles 
being turned by bevel gears), where it drives a pointer at the same rate as 
the main shaft. 




MISCELLANEOUS. 753 



Telephones. 

In the telephone system used there is no "Central" station; but each 
telephone is provided with a transfer switch, by means of which it can be 
directly connected with the other telephones. An annunciator is provided 
to show what station has made the call. The ringing and talking circuits 
are entirely separate, and ringing is done by battery current. 

To make a call, the transfer switch is turned so that the pointer is over 
the name of the station desired, and a push-button pressed. This rings the 
bell, and causes the annunciator at the desired station to indicate the name 
of the station calling ; then the person called turns his transfer switch to 
agree with the indication of the annunciator, which connects the two tele- 
phones directly with each other, and allows talking to proceed. 

Bell Company's telephones are used, and are mounted in water-tight 
cases ; all accessories are made water-tight. 

Jfire Alarms. 

The fire-alarm system consists of mercurial thermostats, located in all 
parts of the ship, and connected to an annunciator in the captain's office. 

The thermostats consist of a hermetically sealed metal, tube containing 
mercury, and provided with an insulated platinum point, so adjusted that 
at a temperature of 200° F. the mercury will have expanded sufficiently to 
make contact with the platinum, thus completing the circuit, and indicat- 
ing at the annunciator the location of the heated thermostat. The annun- 
ciator is provided with a bell which Avill ring continuously until a switch 
corresponding to the indicating drop is opened. Battery current is used. 

Water-tig-Iit Door Alarms. 

To give a general signal for the closing of all water-tight doors, a system 
of alarm whistles is used. The whistle consists of a solenoid which pulls 
its core down into an air chamber, and thus forces the air out through a 
small shrill whistle. The core is restored by spiral springs. Ail whistles 
are connected in parallel, and are operated by a make and break mechan- 
ism, which by the pulling of a lever will interrupt the circuit continuously 
for about 30 seconds, each interruption giving a blast from each whistle. 
Current from the lightning mains is used. 

*4>S/S:.YOIl» AliAjaUI WHIiTLE. 

The construction is shown in Fig. 12. The clockworks for operating the 
contact maker is constructed so that by rotating an operating lever it is 
wound up, and upon releasing the lever it vibrates the contact while running 
down, thus giving periodical signals. 

Call Bells. 

An elaborate system of call bells, annunciators, electro-mechanical signal 
gongs, etc., is installed on all large ships. The main difference from ordi- 
nary commercial work is that all appliances are made water-tight. 

unscEi^AanEOUS. 

Range -Finder. 

The following is a brief outline of the principles employed in the instru- 
ment designed by Lieutenant Bradely Fiske of the United States Navy. 
In Fig. 10 let A represent the target and BC a known base. Then 

AC : BC : : sin ABC : sin BAG. 

sin ABC 



AC= BC X 



sin BAG 



The angle ABC can be readily measured. The angle BAC= DBE, the 
line BE being parallel to AC, 



754 ELECTRICITY IN THE UNITED STATES NAVY. 



The Fiske range-finder measures the angle DBE by the use of the Wheat- 
stone bridge, as follows : 

Suppose the two semi-circles in Fig. 10 replaced by two metallic arcs (Fig. 
11). At the center of each of these arcs is pivoted a telescope, the pivot of 
which is connected to a battery B. The telescopes are in electrical contact 
witb the arcs. These metallic* arcs are connected at their extremities with 
a galvanometer, <?, the whole forming a Wheatstone bridge, whose arms are 
aa bb. 

When the telescopes are pointed at the object A, it is evident that the 
arms of the bridge are unequal, and hence do not balance ; and this fact is 
indicated by the deflection of the needle of the galvanometer. The arc FD 




Fig. 10. 



Fig. 11. 



is noted. By swinging the telescope at F around till the needle of the 
galvanometer indicates zero, the bridge balances, the telescope being 
parallel to the one at C, and the arc or angle DF — FE is equal to the 
angle at A. From this the distance AC can be calculated, or read off 
directly on a properly constructed scale. 

Generally, in using the instrument, the telescopes are mounted at a 
distance from the battery, where the view is uninterrupted, while the gal- 
vanometer is at the gun. The observers keep the telescopes constantly 
directed on the target, and the man at the gun balances the bridge by in- 
troducing a variable resistance into the circuit till the needle stands at 
zero This variable resistance is graduated so as to indicate the range 
corresponding to the resistance introduced 

Firing* Crnns. 

Large suns are arranged to use both percussion and electric primers for 
firingr Tbe electric primer is of the same external shape as the percussion 
primers, and is exploded by a fine platinum wire, heated by current from 
tbe cells of a dry battery mounted near the gun A ground'return is used, 
and a safety switch is fastened to the breech plug, so that the circuit can- 
not be completed until the breech plug is closed, A push-button is used to 
complete the circuit and fire the gun, 

Speed Recorder. 

A.n instrument called the " Weaver Speed Recorder " is somewhat used 
for measuring the speed of ships when run on the measured mile, and while 
being launched ; also to measure the acceleration of turrets during test- 
it consists essentially of a clock-works, which drives a paper tape over a 
set of five pens operated by electro-magnets, so that when any magnet is 



MISCELLANEOUS. 



755 




excited it pulls its pen against the moving paper tape, and makes a dot 
thereon. The connecting levers between the magnet and pen are arranged 
something like a piano finger action, so that no matter how long the magnet 
is kept excited, the pen will only make a quick, short dot. All pens are 
located side by side in the same' line, so that if they were all operated at 
the same instant, the result would be a line of dots across the tape. 

When used for measuring mile runs, one pen is connected to a make and 
brake chronometer, so that it makes a dot on the tape every second ; an- 
other pen is connected to a hand push-button, so that a dot can be made at 
the start and finish of the run, and at as many intermediate points as de- 



'56 ELECTRICITY IN THE UNITED STATES NAVY. 



sired ; the other three pens are connected to contact makers on the shafts 
of the main engines, so that a dot is made for every revolution of the en- 
gine. (If the ship has twin screws, of course only two of the remaining 
pens are used ; and if single screw, only one.) 

It is thus seen that by counting the number of second dots between the 
start and tmish dots, the length of time to make the run is given, and by 
counting the number of revolution dots in any desired space, the speed of 
the engine is given. Fractional seconds or revolutions can easily be scaled. 

When used to obtain launching curves, a long steel wire wound on a drum 
has one end attached to the ship, and a contact maker is fastened to this 
drum. As the ship slides out the drum is revolved and dots made on the 
tape at each revolution ; knowing the diameter of the drum, the speed at 
any instant is found by comparison of the revolution dots with the second 
dots. The hand-push is used to mark the start, finish, instant of pivoting, 
and any other desired matters. 

When used for acceleration runs on turrets, the same procedure as for 
launching curves is followed, except the contact maker is attached to some 
rotating part of the turret mechanism. 



MISCELLANEOUS. 



757 



MISCELLANEOUS. 



thermo-electric scam. 

"With respect to lead, at a mean temperature of 20° C. (Matthiessen.) 
The E.M.F.s are in micro-volts per degree centigrade : 



Bismuth of commerce in wire 

" pure " 

" crystallized along axi 

" " normal to 

axis . 

Cobalt 


+97.0 

+89.0 

5 +65.0 

+45.0 
+22.0 
+11.75 
+0.418 
0. 

— 0.1 

— 0.1 

— 0.9 

— 1.2 


Antimony, pure, in wire . — 3.8 
Silver " " . — 3.0 
Zinc " " . — 3.7 
Copper, galvano-plastic . — 3.8 
Antimony of commerce in 


German Silver ..... . 

Mercury 


Arsenic — 13.56 

Iron, piano wire .... — 17.50 
Antimony, crystallized along 

axis ....... — 22.60 


Tin . . 


Copper of commerce .... 

Platinum 

Gold 


Antimony, normal to axis . — 26.40 
Phosphorus (red) .... — 29.70 
Tellurium 502.00 




Selenium —807.00 



CONNECTIONS OF IHTRUCTIOUT COIL. 

(Ruhmkoff's.) 

D. T i T * 




Fig. l. 



Index to Figure. 

T X T 2 = Terminals to which wires from 
B = Battery are attached. 

B — Reverser or commutator for removing or cutting off current. 
CS=z Contact screw platinum-pointed (in primary circuit). 
H= Hammer (soft iron), the movement of which completes and 

breaks circuit at CS. 
C = Condenser for arresting the momentary direct induced current in 
PC= Primary coil of thick wire, through which battery current 



SC : = Secondary coil of fine wire (well insulated) in which sparking 
currents are induced. 



D 1 D % z=z Spark dischargers fitted to ends of secondary 
IC = Iron core, being a bundle of very soft iron wii 



coil. 



POWER IC I <(l I It E S» FOR §EWIIG-IttACHIHE§. 



Light-running . . . 
Heavy work on same . 
Leather-sewing . . . 
Button-hole machines 



20 machines to 1 h.p. 
15 " " " 

12 " " " 

to 12 " « « 



758 



MISCELLANEOUS. 



PHOIiri BRAKE, 




■A 






Constant = J^— = .0001904 
ooOOO 
then 
Horse-power = .0001904 



Fig. 2. 



X d X w X revolutions per minute. 



rOWJER USJEB BY 1IACHIAE-IOOLS. 

(R. E. Dinsmore, from the Electrical World.) 
Shop shafting 2 T 3 g in. X 180 ft. at 160 revs., carrying 26 pulleys 
from 6 in. diam. to 36 in., and running 20 idle machine helts 
Lodge-Davis upright back-geared drill-press with table, 28 in. 
swing, drilling |- in. hole in cast iron, with a feed of 1 in. per 

minute 

Morse twist-drill grinder No. 2, carrying 26 in. wheels at 3200 



1.32 H. P. 



0.78 H. 



0.29 H. 



Pease planer 30 in. x 36 in., table 6 ft., planing cast iron, cut 
\ in. deep, planing 6 sq. in. per minute, at 9 reversals . . . . 1.06 H. 

Shaping-machine 22 in. stroke, cutting steel die, 6 in. stroke, y 
in. deep, shaping at rate of 1.7 square inch per minute . . . 0.37 H. 

Engine-lathe 17 in. swing, turning steel shaft 2f in. diam., cut 

i 3 B deep, feeding 7.92 in. per minute 0.43 H, 

Engine lathe 21 in. swing, boring cast-iron hole 5 in. diam., cut 
j 3 g diam., feeding 0.3 in. per minute 0.23 H. 

Sturtevant No. 2, monogram blower at 1800 revs, per minute, 
no piping 0.8 H. 

Heavy planer 28 in. x 28 in. x 14 ft. bed, stroke 8 in., cutting 
steel, 22 reversals per minute 3.2 H, 



Horse-power in IVfachine-shops; friction; 


Iflen 


Employed. 




(Flather.) 














Horse-power. 




"c3 


6 








> 



> 


o> 


jj 


H 


H 




Kind 






•3 >> 


o & 


3 






Name of Firm. 


of 




-^.3 


~ a 


+5.9 


o 


gw 


2 0> 




Work. 




Ptf 


WM 




u 


^.£ 








£a .H3 


Sjl 




!H 


"•*-< "^ 






■$, 




Ozct 


g 


O 











© 
















H 


Pn 


rt 


P4 


A 


A 


'A 


Lane & Bodley .... 


E. & W.W. 


58 








132 


2.27 




J. A. Fay & Co 


W. W. 


100 


15 


85 


15 


300 


3.00 


3.53 


Union Iron Works . . 


E.,M. M. 


400 


95 


305 


23 


1600 


4.00 


5.24 


Erontier Iron &Brass W'ks 


M.E.,etc. 


25 


8 


17 


32 


150 


6.00 


8.82 


Taylor Mfg. Co 

Baldwin Loco. Works . 


E. 


95 








230 


2.42 




L. 


2500 


2000 


500 


80 


4100 


1.64 


8.20 


W. Sellers & Co. (one de- 


















partment) 


H.M. 


102 


41 


61 


40 


300 


2.93 


4.87 


Pond Machine Tool Co. . 


M. T. 


180 


75 


105 


41 


432 


2.40 


4.11 


Pratt & Whitney Co. . . 


" 


120 








725 


6.04 




Brown & Sharpe Co. . . 




230 








900 


3.91 





MISCELLANEOUS. 



759 



Horse-power in machine-shops. 



Continued. 







Horse-power. 




"oS 


i 
o> 














O 


* 
H 






<D 


o> 


<D 












> 


fl 








Kind 




T3 . 


O £ 


£& 




CD 

ft . 




Name of Firm. 


of 
Work. 


'cS 


if 
1$ 


"3 08 


2 cS 


O 

S 


<D . 

o 


b 
























H 




P3 


P4 


£ 


k; 


fc 


Yale & Towne Co. . . . 


C.&L. 


135 


67 


68 


49 


700 


5.11 


10.25 


Ferracute Machine Co. . 


P.&D. 


35 


11 


24 


31 


90 


2.57 


3.75 


T. B. Wood's Sons . . . 


P. & S. 


12 








30 


2.50 




Bridgeport Forge Co. . 


H. F. 


150 


75 


75 


50 


130 


.86 


1.73 


Singer Mfg. Co 


S.M. 


1300 








3500 


2.69 




Howe Mfg. Co 


" 


350 








1500 


4.28 




Worcester Mach. Screw Co. 


M. S. 


40 








80 


2. 00 




Hartford " " " 


" 


400 


100 


300 


25 


250 


0.62 


0.83 


Nicholson File Co. . . 


F. 


350 








400 


1.14 




Averages 




346.4 






38.6% 


818.3 


2.96 


5.13 



Abbreviations: E., engine ; W.W., wood-working machinery; M. M., 
mining machinery ; M. E., marine engines; L., locomotives; H. M., heavy 
machinery; M. T., machine-tools; C.&L., cranes and locks; P.&D., 
presses and dies; P. & S., pulleys* and shafting; H. F., heavy f orgings ; 
S. M., sewing-machines ; M. S., machine-screws ; F., tiles. 



LIST OJP TOOLi AIlfD SlTJPPJLKEg ESEFVL Il¥ 

OSTALLiafG ELECTMIC ],f C.1HTN JLTM*» 

DYMAMOS. 



1 Tool chest. 

1 Magneto and cable. 

1 Speed indicator. 

1 Tape line, 75 ft. 

1 Pule, 2 ft. 

1 Scraper, for bearings. 

1 Blow lamp. 

1 Clawhammer, No. 13. 

1 Ball pein hammer, No. 24. 

1 B. & S. pocket wrench, No. 4. 

1 Monkey wrench, 10 inch. 

1 Set (2) Champion screw-drivers. 

1 Large screw-driver, 12-inch. 

1 Off-set screw-driver. 

1 Patchet brace, No. 33. 

Bits, J, |, h f , I, h 1 inch. 
1 Clarke Expansive bit, £ to 3 inch. 
1 Screw-driver bit. 
1 Gimlet bit. 
1 Wood countersink. 
1 Extension drill, | in. length, 24 in. 
1 Long or extension gimlet. 
1 Cold chisel , | inch. 
1 Half round cold chisel. 
1 Cape chisel. 

1 Wood chisel, firmer paring, f inch. 
1 Brick drill. 



Files, one each : round, flat, half- 
round and three-square. 
1 Saw, 20 inch. 
1 Hack-saw, 10 inch. 
10 Extra saw blades. 
1 Plumb bob. 
1 Brad awl. 
1 Pair carbon tongs. 
1 Soldering copper, No. 3. 
1 Pound of solder. 
1 Pair of climbers. 
1 Come-along. 
1 Splicing-clamp. 
1 Strap and vise. 
1 Pair line pliers, 8 inch. 
1 Pair of side-cutting pliers, 5 inch. 
1 Pair of diagonal-cutting pliers, 5 in. 
1 Pair of round-nose pliers, 5 inch. 
1 Pair of flat-nose pliers, 5 inch. 

1 Pair of burner pliers, 7 inch. 
6 Sheets of emery cloth. 

6 Sheets of crocus cloth. 

2 Gross of assorted machine screws. 
2 Gross of assorted wood screws. 

150 Special screws. 
Taps, 6-30, 10-24, 12-24, 18-18. 
Drills, 34, 21, 9, 15-64, 
Tap wrench, 



760 



MISCELLANEOUS. 



TOO I,* iu<ti nun 

The following-named tools will probably be required in constructing lines 
for city or commercial lighting : 

(Davis.) 



Article. 



Stubs' pliers, plain .... 
Climbers and straps .... 
Pulley-block and ecc. clamp 
Come-along and strap . . . 

Splicing-clamps 

Linemen's tool-bag and strap 
Soldering-furnace .... 
Gasoline blow-pipes .... 

Soldering coppers 

Pole-hole shovels 

Pole-hole spoon, regular . . 
Octagon digging-bars . . . 

Tamping-bars 

Crowbar 

Pick-axe 

Carrying-hook, heavy . . . 

Cant-hook 

Pike-poles 

Pole-supporter 

Comb, pay-out reel and straps 

Nail-hammer 

Linemen's broad hatchets 

Drawing-knives 

Hand-saw 

Ratchet-brace, bits .... 

Screw-drivers 

Wrench 

Bastard file 



Size. 



Sin. 

*To ' 

No. 3 
B. &S. 



2 1b. 
8 ft. 

7 ft. 

8 ft. 
7 ft. 

10 1b. 



4 ft. 
16 ft. 
6 ft. 

' i lb'. 

6 in. 
12 in. 
26 in. 
10 in. 

8 in. 
12 in. 
12 in. 



Cost 
about 



$2.00 
3.00 
8.00 
2.25 
2.50 
4.80 
6.00 
6.00 

.95 
1.50 
1.25 
3.50 
2.60 

.90 

.75 
6.00 
2.00 
2.40 
12.00 
20.00 
1.00 
1.50 
2.10 
1.50 
3.00 

.80 
1.25 

.30 



APPROXIMATE 1IST ©J? SUPPLIES 



REQUIRED IN INSTALLING 15 CITY LAMPS AND 20 COMMERCIAL LAMPS 
ON A FIVE-MILE CIRCUIT, SETTING POLES 132 FEET APART. 

(Davis.) 



Articles. 


Size or 
Diameter. 


Price 
about 


Quantity. 


Electric-light poles . 
Electric-light poles 
Electric-light poles . 
Cross-arms, 4-pin . . 
Painted oak pins . . 
Oak pins and bolts . 
Iron break-arms . . 
Lag-screws and washers 
Glass insulators, D. G. 






30 ft., 6 in. 
35 ft., 7 in. 
40 ft., 7 in. 

4 ft. 

lMn. 

liin. 

1 X 7 in. 

f X 8 in. 
1 in. 

6 bs' 


$2.40 each 

4.15 " 

5.50 " 

.30 " 

.02 " 

.07 " 

.75 " 

.04 " 

•07£ " 

.05 " 

.07 lb. 

.20 each 

125.00 mi. 


180 

40 ' 
200 
800 

24 

25 

400 

850 

2500 


Guy stranded cable . 
Cross-arm brace and bol 


ts 


500 lbs. 

40 
6 miles 











MISCELLANEOUS. 



761 



MATERIAL ItE^UlEBgEI* FOR 
IAMP§. 

(Davis.) 



CO]¥j¥ECTI]¥« inr 



Sleet-proof pulleys . . . 
Street-lamp cleats, iron 
Arc-lamp cordage .... 
Suspension cable .... 
Hard-rubber tube .... 
Soft-rubber tubing . . . 


I in. 
Jin. 
1 X f in. 

fin. 


$0.75 each,. 

.25 " 
1.25 hd. ft. 

.02* ft. 
1.501b. 

.20 ft. 
3.50 each 

2.40 hd. 

2.50 " 


30 

15 

25 

3000 ft. 

5 lbs. 

200 ft. 

20 


Porcelain insulators and 




400 


Oak brackets and spikes . 




150 



NATIONAL ELECTRICAL CODE." 



RULES AND REQUIREMENTS OF THE NATIONAL BOARD OF 
FIRE UNDERWRITERS FOR THE INSTALLATION OF WIRING 
AND APPARATUS FOR ELECTRIC LIGHT, HEAT, AND POWER 
AS RECOMMENDED BY THE UNDERWRITERS' NATIONAL 
ELECTRIC ASSOCIATION. 

EDITION OF 1901. 

The National Electrical Code, as it is here presented, is the result of the 
united efforts of the various Electrical, Insurance, Architectural, and allied 
interests which have, through the National Conference on Standard Elec- 
trical Rules, composed of delegates from various National Associations, 
unanimously voted to recommend it to their respective Associations for 
approval or adoption. 

The following is a list of the Associations represented in the Conference, 
all of which have approved of the Code : 

American Institute of Architects. 
American Institute of Electrical, Engineers 
American Society of Mechanical Engineers 
American Street Railway Association 
Factory Mutual Fire Insurance Companies 
National Association of Fire Engineers 
National Board of Fire Underwriters 
National Electric Light Association 
Underwriters' National Electric Association 



CMnraitAX PLAM GOVER^TI^G THE ARRAUTGE- 

ME.W OF RULES. 

CLASS A. — Central Stations, Dynamo, Motor, and Storage- 
Battery -Rooms, Transformer Substations, etc. Rules 1 

toll. 
CLASS B. — Outside Work, all systems and voltages. Rules 12 and 13. 
CLASS C — Inside Work. Rules 14 to 39. Subdivided as follows : 

General Rules, applying to all systems and voltages. Rules 14 to 17. 
Constant-Current systems. Rules 18 to 20. 
Constant»T*otential systems. 
All voltages. Rules 21 to 23. 
Yoltage not over 550. Rules 24 to 31. 
Voltage between 550 and 3,500. Rules 32 to 37. 
Voltage over 3,500. Rules 38 and 39. 
CLASS D. — Specification for Wires and Fitting'*- Rules 40 to 63. 
CLASS E. —'Miscellaneous. Rules 64 to 67. 
CLASS F. — Marine Wiring. Rules 68 to SO. 



CiASS A. — STATIONS Al¥» RYIVAMO ROOMS. 

INCLUDES CENTRAL STATIONS, DYNAMO, MOTOR, AND STORAGE-BATTERY 
ROOMS, TRANSFORMER SUBSTATIONS, ETC. 

1. Generators — 

a. Must be located in a dry place. 

b. Must never be placed ita a room where any hazardous process is carried I 
on, nor in places where they would be exposed to inflammabl ~ 
flyings of combustible materials. 

762 



CLASS A. STATIONS AND DYNAMO ROOMS. 763 

c. Must be insulated on floors or base frames, which must be kept filled 
to prevent absorption of moisture, and also kept clean and dry. Where 
frame insulation is impracticable, the Inspection Department having juris- 
diction may, in writing, permit its omission, m which case the frame must 
be permanently and effectively grounded. 

A high-potential machine which, on account of great weight or for other 
reasons, cannot have its frame insulated from the ground, should be sur- 
rounded with an insulated platform. This may be made of wood, mounted 
on insulating supports, and so arranged that a man must always stand upon 
it in order to touch any part of the machine. 

In case of a machine having an insulated frame, if there is trouble from 
static electricity due to belt friction, it should be overcome by placing near 
the belt a metallic comb connected with the earth, or by grounding the 
frame through a very high resistance of not less than 200 ohms per volt 
generated by the machine.. 

d. Every constant-potential generator must be protected from excessive 
current by a safety fuse, or equivalent device, of approved design in each 
lead wire. 

These devices should be placed on the machine or as near it as possible. 

Where the needs of the service make these devices impracticable, the 
Inspection Department having jurisdiction may, in writing, modify the 
requirements. 

e. Must each be provided with a waterproof cover. 

f. Must each be provided with a name-plate, giving the maker's name, 
the capacity in volts and amperes, and the normal speed in revolutions per 
minute. 

2. Conductors — 

From generators to switchboards, rheostats, or other instruments, and 
thence to outside lines. 

a. Must be in plain sight or readily accessible. 

b. Must have an approved insulating covering as called for by rules in 
Class "C" for similar work, except that in central stations, on exposed 
circuits, the wire which is used must have a heavy braided non-combustible 
outer covering. 

Bus bars may be made of bare metal. 

c. Must be kept so rigidly in place that they cannot come in contact. 

d. Must in all other respects be installed under the same precautions as 
required by rules in Class " C " for wires carrying a current of the same 
volume and potential. 

3. Switchboards — 

a. Must be so placed as to reduce to a minimum the danger of communi- 
cating fire to adjacent combustible material. 

Special attention is called to the fact that switchboards should not be 
built down to the floor, nor up to the ceiling, but a space of at least ten 
or twelve inches should be left between the floor and the board, and from 
eighteen to twenty-four inches between the ceiling and the board in order 
to prevent fire from communicating from the switchboard to the floor or 
ceiling, and also to prevent the forming of a partially concealed space very 
liable to be used for storage of rubbish and oily waste. 

b. Must be made of non-combustible material or of hardwood in skeleton 
form filled to prevent absorption of moisture. 

c. Must be .accessible from all s-ides when the connections are on the back, 
but may be placed against a brick or stone wall when the wiring is entirely 
on the face. 

d. Must be kept free from moisture. 

e. Bus bars must be equipped in accordance with rules for placing 
conductors. 

4. Resistance Boxes and Equalizers — 

(For construction rules, see -ZVo. 60.) 

a. Must be placed on a switchboard or, if not' thereon, at a distance of a 
a foot from combustible material, or separated therefrom by a non-inflam- 
mable, non-absorptive, insulating material. 



764 NATIONAL ELECTRICAL CODE. 

5. .Lightning* Arresters — 

{For construction rules see No. 63.) 

a. Must be attached to each side of every overhead circuit connected with 
the station. 

It is recommended to all electric lightand power companies that arresters 
be connected at intervals over systems in such numbers and so located as to 
pi event ordinary discharges entering (over the wires) buildings connected 
to the lines. 

b. Must be located in readily accessible places away from combustible 
materials, and as near as practicable to the point where the wires enter the 
building. 

Station arresters should generally be placed in plain sight on the switch 
board. 

In all cases, kinks, coils, and sharp bends in the wires between the 
ajresters and the outdoor lines must be avoided as far as possible. 

c. Must be connected with a thoroughly good and permanent ground con- 
nection by metallic strips or wires having a conductivity not less than that 
of a No. 6 B. & S. copper wire, which must be run as nearly in a straight 
line as possible from the arresters to the earth connection. 

Ground wires for lightning arresters must not be attached to gas-pipes 
within the buildings. 

It j,s often desirable to introduce a choke coil in circuit between the 
arresters and the dynamo. In no case should the ground wire from a 
lightning arrester be put into iron pipes, as these would tend to impede the 
discharge. 

©. Care and. Attendance. 

a. A competent man must be kept on duty where generators are operating. 

b. Oily waste must be kept in approved metal cans and removed daily. 
Approved waste cans shall be made of metal, with legs raising can three 

inches from the floor, and with self-closing covers. 

?. Vesting* of Insulation Resistance. 

a. All circuits, except such as are permanently grounded in accordance 
with Rule 13 A, must be provided with reliable ground detectors. Detectors 
which indicate continuously, and give an instant and permanent indication 
of a ground, are preferable. Ground wires from detectors must not be 
attached to gas-pipes within the building. 

b. Where continuously indicating detectors are not feasible, the circuits 
should be tested at least once per day, and preferably oftener. 

c. Data obtained from all tests must be preserved for examination by the 
Inspection Department having jurisdiction. 

These rules on testing to be applied at such places as may be designated 
by the Inspection Department having jurisdiction. 

8. Motors — 

a. Must be insulated on floors or base frames, which must be kept filled 
to prevent absorption of moisture ; and must be kept clean and dry. Where 
frame insulation is impracticable the Inspection Department having juris- 
diction may, in writing, permit its omission, in which case the frame must 
be permanently and effectively grounded. 

A high-potential machine which, on account of great weight or for other 
reasons, cannot have its frame insulated, should be surrounded with an 
insulated platform. This may be made of wood mounted on insulating 
supports, and so arranged that a man must stand upon it in order to touch 
any part of the machine. 

In case of a machine having an insulated frame, if there is trouble from 
static electricity due to belt friction, it should be overcome by placing near 
the belt a metallic comb connected to the earth, or by grounding the frame 
through a very high resistance of not less than 200 ohms per volt generated 
by the machine. 

b. Must be wired under the same precautions as required by rules in class 
" C," for wires carrying a current of the same volume and potential. 

The leads or branch circuits should be designed to carry a current at least 
fifty per cent greater than that required by the rated capacity of the motor 



CLASS A. STATIONS AND DYNAMO ROOMS. 765 

to provide for the inevitable overloading of the motor at times without 
overf using the wires. 

c. The motor and resistance box must be protected by a cutout and con- 
trolled by a switch (see No. 17 a), said switch plainly indicating whether 
"on" or "off." Where one-fourth horse-power or less is used on low- 
tension circuits a single-pole switch will be accepted. The switch and 
rheostat must be located within sight of the motor, except in such cases 
where special permission to locate them elsewhere is given in writing by 
the Inspection Department having jurisdiction. 

d. Must have their rheostats or starting-boxes located as to conform to 
the requirements of No. 4. 

In connection with motors the use of circuit-breakers, automatic start- 
ing-boxes and automatic under-load switches is recommended, and they 
must be used when required. 

e. Must not be run in series-multiple or multiple-series, except on con- 
stant-potential systems, and then only by special permission of the Inspec- 
tion Department having jurisdiction. 

/. Must be covered with a waterproof cover when not in use, and, if 
deemed necessary by the Inspection Department having jurisdiction, must 
be inclosed in an approved case. 

From the nature of the question the decision as to what is an approved 
case must be left to the Inspection Department having jurisdiction to de- 
termine in each instance. 

g. Must, when combined with ceiling fans, be hung from insulated hooks, 
or else there must be an insulator interposed between the motor and its 
support. 

h. Must each be provided with a name-plate, giving the maker's name, 
the capacity in volts and amperes, and the normal speed in revolutions 
per minute. 

O. Railway Power Plants. 

a. Must be equipped in each feed wire before it leaves the station with 
an approved automatic circuit-breaker (see No. 52) or other device, which 
will immediately cut off the current in case of an accidental ground. This 
device must be mounted on a fireproof base, and in full view and reach of 
the attendant. 

1©. Storagre or Primary .Batteries. 

a. When current for light and power is taken from primary or secondary 
batteries, the same general regulations must be observed as applied to 
similar apparatus fed from dynamo generators developing the same differ- 
ence of potential. 

6. Storage battery rooms must be thoroughly ventilated. 

c. Special attention is directed to the rules for rooms where acid fumes 
exist (see No. 24, j and k). 

d. All secondary batteries must be mounted on non-absorptive, non- 
combustible insulators, such as glass or thoroughly vitrified and glazed 
porcelain. 

e. The use of any metal liable to corrosion must be avoided in cell con- 
nections of secondary batteries. 

11. Transformers. 

{For construction rules, see No. 62.) 

a. In central or substations the transformers must be so placed that 
smoke from the burning out of the coils or the boiling over of the oil 
(where oil-filled cases are used) could do no harm. 



CUASS B. — OUTSIDE WORK 

ALL SYSTEMS AND VOLTAGES. 

13. Wires. 

a. Service wires must have an approved rubber insulating covering (see 
No. 41). Line wires, other than services, must have an approved weather- 

Eroof, or rubber insulating covering (Nos. 41 and 44). All the wires must 
ave an insulation equal to that of the conductors they confine. 



766 NATIONAL ELECTRICAL CODE. 



6. Must be so placed that moisture cannot form a cross connection be- 
tween them, not less than a foot apart, and not in contact with any sub- 
stance other than their insulating supports. Service blocks must be covered 
over their entire surface with at least two coats of waterprooi paint. 

c. Must be at least seven feet above the highest point of flat roofs, and 
at least one foot above the ridge of pitched roofs over which they pass or to 
which they are attached. 

d. Must be protected by dead insulated guard iron or wires from pos- 
sibility of contact with other conducting wires or substances to which cur- 
rent may leak. Special precautions of this kind must be taken where sharp 
angles occur, or where any wires might possibly come in contact with 
electric light or power wires. 

e. Must be provided with petticoat insulators of glass or porcelain. Por- 
celain knobs or cleats and rubber hooks will not be approved. 

/. Must be so spliced or joined as to be both mechanically and electri- 
cally secure without solder. The joints must then be soldered, to insure 
preservation, and covered with an insulation equal to that on the con- 
ductors. 

All joints must be soldered, even if made with some form of patent spli- 
cing device. This ruling applies to joints and splices in all classes of wiring 
covered by these rules. 

g. Must, where they enter buildings, have drip loops outside, and the 
holes through which the conductors pass must be bushed with non-combus- 
tible, non-absorptive insulating tubes slanting upward toward the inside. 

h. Telegraph, telephone, and similar wires must not be placed on the 
same cross-arm with electric light or power wires ; and when placed on the 
same pole with such wires the distance between the two inside pins of each 
cross-arm must not be less than twenty-six inches. 

i. The metallic sheaths to cables must be permanently and effectively 
connected to " earth." 

TROLLEY WIRES. 

j. Must not be smaller than No. B. & S. copper or No. 4 B. & S. silicon 
bronze, and must readily stand the strain put upon them when in use. 

k. Must have a double insulation from the ground. In wooden-pole con- 
struction the pole will be considered as one insulation. 

I. Must be capable of being disconnected at the power plant, or of being 
divided into sections, so that, in case of fire on the railway route, the cur- 
rent may be shut off from the particular section and not interfere with the 
work of the firemen. This rule also applies to feeders. 

m. Must be safely protected against accidental contact where crossed by 
other conductors. 

Guard wires should be insulated from the ground, and should be electric- 
ally disconnected in sections of not more than 300 feet in length. 

GROUND RETURN WIRES. 

n. For the diminution of electrolytic corrosion of underground metal 
work, ground return wires must be so arranged that the difference of 
potential between the grounded dynamo terminal and any point on the 
return circuit will not exceed twenty -five volts. 

It is suggested that the positive pole of the dynamo be connected to the 
trolley line, and that whenever pipes or other underground metal work are 
found to be electrically positive to the rails or surrounding earth, that they 
be connected by conductors arranged so as to prevent as far as possible 
current flow from the pipes into the ground. 

13. Transformers. 

(For construction rules, see No. 62.) 

a. Must not be placed inside of any building, excepting central stations, 
unless by special permission of the Inspection Department having juris- 
diction. 

b. Must not be attached to the outside walls of buildings, unless sep- 
arated therefrom by substantial supports. 



CLASS B. OUTSIDE WORK. 767 



13. A., ©rounding" Low Potential Circuits. 

The grounding of low potential circuits under the folloioing regulations is 
only allowed when so arranged that under normal conditions there will be no 
flow of current through the ground wire. 

Direct Current 3-Wfire Systems. 

a. Neutral wire may be grounded, and when grounded the following 
rules must be complied with : — 

1. Must be grounded at the Central Station on a metal plate buried in 
coke beneath permanent moisture level, and also through all available 
underground Avater- and gas-pipe systems. 

2. In underground systems the neutral wire must also be grounded at 
each distributing-box through the box. 

3. In overhead systems the neutral wire must be grounded every 500 feet, 
as provided in Sections c, e, and/. 

The Inspection Department having jurisdiction may require grounding if 
they deem it necessary. 

Two-wire direct current systems having no accessible neutral point are 
not to be grounded. 

Alternating- Current Secondary Systems. 

b. The neutral point of transformers, or the neutral wire of distributing 
systems, may be grounded, and when grounded the following rules must be 
complied with : — 

1. Transformers feeding 2-wire systems must be grounded at the center 
of the secondary coils. 

2. Transformers feeding systems with a neutral wire must have the 
neutral wire grounded at the trausformer and at least every 250 feet 
beyond. 

Inspection Department having jurisdiction may require grounding if they 
deem it necessary. 

©round Connections. 

c. The ground wire in D. C. 3-wire systems must not at Central Stations 
be smaller than the neutral wire and not smaller than No. 6 B. & S. else- 
where. 

d. The ground wire in A. C. systems must never be less than No. 6 B. & 
S., and must always have equal carrying capacity to the secondary lead of 
the transformer, or the combined leads where transformers are banked. 

e. The ground wire must be kept outside of buildings, but may be di- 
rectly attached to the building or pole. The wire must be carried in as 
nearly a straight line as possible, and kinks, coils and sharp bends must be 
avoided. 

/. The ground connections for Central Stations, transformer sub- 
stations, and banks of transformers must be made through metal plates 
buried in coke below permanent moisture level, and connections should also 
be made to all available underground piping systems. For individual 
transformers and building services the ground connection may be made as 
above, or may be made to water or other piping systems running into the 
buildings. This connection may be made by carrying the ground wire into 
the cellar and connecting on the street side of meters, main clocks, etc. 

In connecting ground wires to piping systems, where possible the wires 
should be soldered into one or more brass plugs and tbe plugs forcibly 
screwed into a pipe-fitting, or where the pipes are cast iron into a hole 
tapped to the pipe itself. For large stations, where connecting to under- 
ground pipes with bell and spigot joints, it is well to coni-.ect to several 
lengths, as the pipe joints may be of rather high resistance. Where such 
plugs cannot be used the surface of the pipe may be filed or scraped bright, 
the wire wound around it, and a strong clamp put over the wire and firmly 
bolted together. 

Where ground plates are used a No. 16 copper plate, about 3x6 feet in 
size, with about two feet of crushed coke or charcoal about pea. size both 
under and over it, would make aground of sufficient capacity for a mod- 
erate size station, and would probably answer for the ordinary sub-station 



768 NATIONAL ELECTRICAL CODE. 



or bank of transformers. For a large Central Station considerable more 
area might be necessary, depending upon the other underground connec- 
tions available. The ground Avire should be riveted to such a plate in a 
number of places, and soldered for its whole length. Perhaps even better 
than a copperplate is a cast-iron plate with projecting forks, the idea of the 
fork being to distribute the connection to the ground over a fairly broad 
area, and to give a large surface contact. The ground wire can probably 
best be connected to such a cast-iron plate by brass plugs screwed into the 
plate to which the wire is soldered. In all cases the joint between the plate 
and the ground wire should be thoroughly protected against corrosion by 
suitable painting with waterproof paint or some equivalent. 



CLASS C. — IHTSIOE WORK. 

ALL SYSTEMS AND VOLTAGES. 
GEIERAI RULES — ALL SYSTFMS A Hf I» VOLTAGES. 
14. Wires. 

{For special rules, See Nos. 18, 24, 32, 38, and 39.) 

a. Must not be of smaller size than No. 14 B. & S., except as allowed 
under Rules 24 t and 45 b. 

b. Tie wires must have an insu]ation equal to that of the conductors they 
confine. 

c. Must be so spliced or joined as to be both mechanically and electrically 
secure without solder ; they must be then soldered to insure preservation, 
and the joint covered with an insulation equal to that on the conductors. 

Standard wires must be soldered before being fastened under clamps or 
binding screws ; and, when they have a conductivity greater than No. 10 B. 
& S. copper wire, they will be soldered into lugs. 

All joints must be soldered, even if made with some form of patent 
splicing device. This ruling applies to joints and splices in all classes of 
wiring covered by these rules. 

d. Must be separated from contact with walls, floors, timbers, or parti- 
tions through which they may pass by non-combustible, non-absorptive 
insulating tubes, such as glass or porcelain. 

Bushings must be long enough to bush the entire length of the hole in one 
continuous piece, or else the hole must first be bushed by a continuous 
waterproof tube, which may be a conductor, such as iron pipe ; the tube 
then is to have a non-conducting bushing pushed in at each end so as to 
keep the wire absolutely out of contact with the conducting pipe. 

e. Must be kept free from contact with gas, water, or other metallic 
piping, or any other conductors or conducting material which they may 
cross, by some continuous and firmly fixed non-conductor, creating a sepa- 
ration of at least one inch. Deviations from this rule may sometimes be 
allowed by special permission. 

/. Must be so placed in wet places that an air space will be left between 
conductors and pipes in crossing, and the former must be run in such a way 
that they cannot come in contact with the pipe accidentally. Wires should 
be run over, rather than under, pipes upon which moisture is likely to 
gather or which, by leaking, might cause trouble on a circuit. 

15. Underground Conductors — 

a. Must be protected, when brought into a building, against moisture and 
mechanical injury, and all combustible material must be kept removed 
from the immediate vicinity. 

b. Must not be so arranged as to shunt the current through a building 
around any catch-box. 

lO. Table Carrying- Capacity of Wires. 

Below is a table which must be followed in placing interior conductors, 
showing the allowable carrying capacity of wires and cables of ninety-eight 
per cent conductivity, according to the standard adopted by the American 
Institute of Electrical Engineers. 



CLASS C. 



INSIDE WORK. 



'69 





Table A. 


Table B. 






Table A. 


Table B. 


6 


Rubber- 


Weather- 






Rubber- 


Weather- 


ce 


Covered 


proof 






Covered 


proof 


Wires. 


Wires. 


Circular 


Circular 


Wires. 


Wires. 


<% 


See No. 41. 


See No. 


Mils. 


Mils. 


See No. 41. 


See No. 


m 




42 to 44. 








42 to 44. 




Amperes. 


Amperes. 






Amperes. 


Amperes. 


18 


3 


5 


1,624 


200,000 


200 


300 


16 


6 


8 


2,583 


300,000 


270 


400 


14 


12 


16 


4,107 


400,000 


330 


500 


12 


17 


23 


6,530 


500,000 


390 


590 


10 


24 


32 


10,380 


600,000 


450 


680 


8 


33 


46 


16,510 


700,000 


500 


760 


6 


46 


65 


26,250 


800,000 


550 


840 


5 


54 


77 


33,100 


900,000 


600 


920 


4 


65 


92 


41,740 


1,000,000 


650 


1,000 


3 


76 


110 


52,630 


1,100,000 


690 


1,080 


2 


90 


131 


66,370 


1,200,000 


730 


1,150 


1 


107 


156 


83,690 


1,300,000 


770 


1,220 





127 


185 


105,500 


1,400,000 


810 


1,290 


00 


150 


220 


133,100 


1,500 000 


850 


1,360 


000 


177 


262 


167,800 


1,600,000 


890 


1,430 


0000 


210 


312 


211,600 


1,700,009 
1.800,000 
1,900,000 
2,000,000 


930 

970 

1,010 

1,050 


1,490 
1,550 
1,610 
1,670 



The lower limit is specified for rubber-covered wires to prevent gradual 
deterioration of the high insulations by the heat of the wires, but not from 
fear of igniting the insulation. The question of drop is not taken into con- 
sideration in the above tables. 

The carrying capacity of sixteen and eighteen wire is given, but no 
smaller than fourteen is to be used, except as allowed under Rules 2it 
and 45 b. 

T7. Switches, Cutouts, Circuit-Breakers, etc. — 

(For construction rules, see Nos. 51, 52, and 53.) 

a. Must, whenever called for, unless otherwise provided (for exceptions, 
see No. 8 c and No. 22 c), be so arranged that the cutouts will protect, and 
the opening of the switch or circuit-breaker Avill disconnect, all of the 
wires ; that is, in a two-wire system the two wires, and in a three-wire 
system the three wires, must be protected by the cutout, and disconnected 
by the operation of the switch or circuit-breaker. 

b. Must not be placed in the immediate vicinity of easily ignitible stuff or 
where exposed to inflammable gases or dust or to flyings of combustible 
material. 

c. Must, when exposed to dampness, either be inclosed in a waterproof 
box or mounted on porcelain knobs, 

COWSTAUT CUMlEIIfT SYSTEMS. 



PRINCIPALLY SERIES ARC LIGHTING. 

IS. Wires — 

(See also Nos. 14, 15, and 16.) 

a. Must have an approved rubber insulating covering (see No. 41). 

6. Must be arranged to enter and leave the building through an approved 
double-contact service switch (see No. 51), mounted in a non-combustible 
case, kept free from moisture, and easy of access to police or firemen. So- 
called " snap switches " must not be used on high-potential circuits. 



770 NATIONAL ELECTRICAL CODE. 



c. Must always be in plain sight, and never incased, except when required 
by the Inspection Department having jurisdiction. 

d. Must be supported on glass or porcelain insulators, which separate the 
wire at least one inch from the surface wired over, and must be kept rigidly 
at least eight inches from each other, except within the structure of lamps, 
on hanger-boards, in cutout boxes, or like places, where a less distance is 
necessary. 

e. Must, on side walls, be protected from mechanical injury by a sub- 
stantial boxing, retaining an air space of one inch around the conductors, 
closed at the top (the wires passing through bushed holes), and extending 
not less than seven feet from the floor. When crossing floor-timbers in 
cellars or in rooms, where they might be exposed to injury, wires must be 
attached by their insulating supports to the underside of a wooden strip not 
less than one-half an inch in thickness. 

XO. Arc JLamps — 

(For construction rules, see No. 57.) 

a. Must be carefully isolated from inflammable material. 

b. Must be provided at all times with a glass globe surrounding the arc, 
securely fastened upon a closed base. No broken or cracked globes to be 
used. 

c. Must be provided with a wire netting (having a mesh not exceeding one 
and one-fourth inches) around the globe, and an approved spark arrester 
(see No. 58), when readily inflammable material is in the vicinity of the 
lamps, to prevent escape of sparks, melted copper or carbon. It is recom- 
mended that plain carbons, not copper-plated, be used for lamps in such 
places. 

Arc lamps, when used in places where they are exposed to flyings of easily 
inflammable material, should have the carbons inclosed completely in a 
globe in such manner as to avoid the necessity for spark arresters. 

For the present, globe and spark arresters will not be required on so- 
called " inverted arc" lamps, but this type of lamp must not be used where 
exposed to flyings of easily inflammable materials. 

d. Where hanger-boards (see No. 56) are not used, lamps must be hung 
from insulating supports other than their conductors. 

30. Incandescent lamps in Series Circuits — 

a. Must have the conductors installed as provided in No. 18, and each 
lamp must be provided with an automatic cutout. 

b. Must have each lamp suspended from a hanger-board by means of rigid 
tube. 

c. No electro-magnetic device for switches and no system of multiple- 
series or series-multiple lighting Avill be approved. 

d. Under no circumstances can they be attached to gas fixtures. 

coursxAiYT pote^tiai, systems. 

GENERAL RULES, ALL VOLTAGES. 

21. Automatic Cutouts (Fuses and Circuit-Breakers). 
(See No. 17, and for construction Nos. 52 and 53.) 

a. Must be placed on all service wires, either overhead or underground, 
as near as possible to the point where they enter the building and inside 
the Avails, and arranged to cut off the entire current from the building. 

Where the switch required by rule No. 22 is inside the building, the cut- 
out required by this section must be placed so as to protect it. 

b. Must be placed at every point where a change is made in the size of 
wire [unless the cutout in the larger wire will protect tbe smaller (see 
No. 16)]. 

c. Must be in plain sight, or inclosed in an approved box (see No. 54) and 
readily accessible. They must not be placed in the canopies or shells of 
fixtures. 



CONSTANT POTENTIAL SYSTEMS. 771 



d. Must be so placed that no set of incandescent lamps, whether grouped 
on one fixture or several fixtures or pendants, requiring more than 660 
watts, shall be dependent upon one cutout. Special permission may be given 
in writing by the Inspection Department having jurisdiction for departure 
from this rule in case of large chandeliers, stage borders, and illuminated 
signs. 

e. Must be provided with fuses, the rated capacity of Avhich does not 
exceed the allowable carrying capacity of the wire ; and, when circuit- 
breakers are used, they must not be set more than about thirty per cent 
above the allowable carrying capacity of the wire, unless a fusible cutout 
is also installed in the circuit (see No. 16). 

33. Switches — 

(See No. 17, and for construction No. 51.) 

a. Must be placed on all service wires, either overhead or underground, 
in a readily accessible place, as near as possible to the point where the 
wires enter the building, and arranged to cut off the entire current. 

b. Must always be placed in dry, accessible places, and be grouped as far 
as possible. Knife switches must be so placed that gravity will tend to open 
rather than close the switch. 

c. Must not be single-pole, except when the circuits which they control 
supply not more than six 16-candle power lamps or their equivalent. 

d. Where flush-switches are used, whether with conduit systems or not, 
the switches must be inclosed in boxes constructed of or lined with fire- 
resisting material. No push-buttons for bells, gas-lighting circuits or the 
like shall be placed in the same wall-plate with switches controlling elec- 
tric light or power wiring. 

33. Electric Heaters — 

a. Must, if stationary, be placed in a safe situation, isolated from inflam- 
mable materials, and be treated as sources of heat. 

b. Must each have a cutout and indicating -switch, (see No. 17 a). 

c. Must have the attachments of feed wires to the heaters in plain sight, 
easily accessible, and protected from interference, accidental or otherwise. 

d. The flexible conductors for portable apparatus, such as irons, etc., 
must have an approved insulating covering (see No. 45 h). 

e. Must each be provided with name-plate, giving the maker's name and 
the normal capacity in volts and amperes. 

IOW POXESTIAI SYSTEMS. 
550 VOLTS OR LESS. 

Jny circuit attached to any machine, or combination of machines, which 
develops a difference of potential, between any two ivires, of over ten 
volts and less than 550 volts, shall be considered as a low-potential 
circuit, and as coming under this class, unless an approved transform- 
ing device is used, which cuts the difference of potential down to ten 
volts or less. The primary circuit not to exceed a potential of 3,500 
volts. 

3-1. Wires — 

GENERAL RULES. 

(See also Nos. 14, 15, and 16.) 

i». Must not be laid in plaster, cement, or similar finish. 

6. Must never be fastened with staples. 

c. Must not be fished for any great distance, and only in places where the 
inspector can satisfy himself that the rules have been complied with. 

d Twin wires must never be used, except in conduits, or where flexible 
conductors are necessary. 

c. Must be protected on side walls from mechanical injury. When cross- 
ing floor-timbers in cellars or in rooms, where they might be exposed to 
injury, wires must be attached by their insulating supports to the under 
side of a wooden strip, not less than one-half inch in thickness, and not less 
than three inches in width. 



772 NATIONAL ELECTRICAL CODE. 



Suitable protection on side walls may be secured by a substantial boxing, 
retaining an air space of one inch around the conductor, closed at the top 
(the wires passing through bushed holes), and extending not less than five 
feet from the floor ; or by an iron-armored or metal-sheathed insulating 
conduit sufficiently strong to withstand the strain it will be subjected to ; 
or plain metal pipe, lined with insulating tubing which must extend one- 
half inch beyond the end of the metal tube. 

The pipe must extend not less than five feet above the floor, and may 
extend through the floor in place of a floor bushing. 

If iron pipes are used with alternating currents, the two or more wires of 
a circuit must be placed in the same conduit. In this case the insulation of 
each wire must be reinforced by a tough conduit tubing projecting beyond 
the ends of the iron pipe at least two inches. 

/. When run immediately under roofs, or in proximity to water tanks or 
pipes, will be considered as exposed to moisture. 

SPECIAL RULES. 

For open work : 

In dry places : 

g. Must have an approved rubber or " slow-burning" waterproof insula- 
tion (see Nos. 41 and 42). 

h. Must be rigidly supported on non-combustible, non-absorptive insula- 
tors, which separate the wires from each other and from the surface wired 
over in accordance with following table : 

VOLTAGE. DISTANCE FROM SURFACE. DISTANCE BETWEEN WIRES. 

to 225 I inch. 2£ inches. 

225 "550 1 " 4 " 

Rigid supporting requires under ordinary conditions, where wiring along 
flat surfaces, supports at least every four and one-half feet. If the wires are 
liable to be disturbed, the distance between supports should be shortened. 
In buildings of mill construction, mains of No. 8 B. & S. wire or over, 
where not liable to be disturbed, may be separated about four inches, and 
run from timber to timber, not breaking around, and may be supported at 
each timber only. 

This rule will not be interpreted to forbid the placing of the neutral of a 
three-wire system in the center of a three-wire cleat, provided the outside 
wires are separated in accordance with above table. 

In damp places, such as Breweries, Sugar Houses, Packing Houses, Stables, 
Dye Houses, Paper or Pulp Mills, or buildings specially liable to 
moisture, or acid, or other fumes liable to injure the wires or their insu- 
lation, except where used for pendants : 

i. Must have an approved rubber insulating covering (see No. 41). 

j. Must be rigidly supported on non-combustible, non-absorptive insula- 
tors, which separate the wire at least one inch from the surface wired over, 
and they must be kept apart at least two and one-half inches. 

Rigid supporting requires under ordinary conditions, where wiring over 
flat surfaces, supports at least every four and one-half feet. If the wires 
are liable to be disturbed, the distance between supports should be 
shortened. In buildings of mill construction, mains of No. 8 B. & S. wire or 
over, where not liable to be disturbed, may bo separated about four inches, 
and run from timber to timber, not breaking around, and may be supported 
at each timber only. 

k. Must have no joints or splices. 

For molding- work : 

I. Must have approved rubber insulation covering (see No. 41). 
m. Must never be placed in molding in concealed or damp places. 

For conduit work : 



n. Must have an approved rubber insulating covering (see No. 47). 
o. Must not be drawn in until all mechanical work on the building has 
been, as far as possible, completed. 



is 



LOW POTENTIAL SYSTEMS. 773 

p. Must, for alternating systems, have the two or more wires of a circuit 
drawn in the same conduit. 

It is advised that this be done for direct-current systems also, so that 
they may be changed to alternating systems at any time, induction troubles 
preventing such a change unless this construction is followed. 

JFor concealed " knob and tube " work : 

q. Must have an approved rubber insulating covering (see No. 41;. 

r. Must be rigidly supported on non-combustible, non-absorptive insula- 
tors which separate the wire at least one inch from the service wired over, 
and must be kept at least ten inches apart, and, when possible, should be 
run singly on separate timbers or studding. 

Rigid supporting requires under ordinary conditions, where wiring along 
flat surfaces, supports at least every four and one-half feet. If the wires are 
liable to be disturbed, the distance between supports should be shortened. 

s. When, from the nature of the case, it is impossible to place concealed 
wiring on non-conbustible, insulating supports of glass or porcelain, an ap- 
proved armored cable with single or tAvin conductors (see No. 48) may be 
used where the difference of potential between wires is not over 300 volts, 
provided it is installed without joints between outlets, and the cable armor 
properly enters all fittings and is rigidly secured in place ; or, if the differ- 
ence of potential between Avires is not over 300 volts, and if AAires are not 
exposed to moisture, they may be fished on the loop system if separately 
incased throughout in approved flexible tubing or conduits. 

For fixture work : 

t. Must have an approved rubber insulating covering (see No. 46), and 
shall not be less in size than No. 18 B. & S. 

u. Supply conductors, and especially the splices to fixtures wires, must 
be kept clear of the grounded part of gas-pipes ; and, Avhere shells are used, 
the latter must be constructed in a manner affording sufficient area to 
allow this requirement. 

v. Must, when fixtures are wired outside, be so secured as not to be cut 
or abraded by the pressure of the fastenings or motion of the fixture. 

25. Interior Conduits. 

(Seealso JVbs. 24 n top, and 49.) 

The object of a tube or conduit is to facilitate the insertion or extraction 
of the conductors to protect them from mechanical injury and, as far as 
possible, from moisture. Tubes or conduits are to be considered merely as 
raceways, and are not to be relied upon for insulation between Avire and 
wire, or between the wire and the ground. 

a. No conduit tube having an internal diameter of less than five-eights 
of an inch shall be used. (If conduit is lined, measurement to be taken 
inside of lining.) 

b. Must be continuous from one junction box to another or to fixtures, 
and the conduit tube must properly enter all fittings. 

c. Must be first installed as a complete conduit system, without the con- 
ductors. 

d. Must be eqtiipped at every outlet with an approved outlet box. 

e. Metal conduits, where they enter junction boxes, and at all other out- 
lets, etc., must be fitted with a capping of approved insulating material, 
fitted so as to protect Avire from abrasion. 

/. Must have the metal of the conduit permanently and effectively 
grounded. 

2G. Fixtures — 

(See also No. 24 t to v.) 

a. Must, when supported from the gas-piping of a building, be insulated 
from the gas-pipe system by means of approved insulating joints (see No. 
59) placed as close as possible to the ceiling. 

It is recommended that the gas outlet pipe be protected above the insulat- 
ing joint by a non-combustible, non-absorptive insulating tube, having a 
flange at the lower end where it comes in contact Avith the insulating joint ; 



774 NATIONAL ELECTRICAL CODE. 



and that, where outlet tubes are used, they be of sufficient length to extend 
below the insulating joint, and that they be so secured that they will not be 
pushed back when the canopy is put in place. Where iron ceilings are 
used, care must be taken to see that the canopy is thoroughly and perma- 
nently insulated from the ceding. 

b. Must have all burs, or tins, removed before the conductois are drawn 
into the fixture. 

c. The tendency to condensation within the pipes should be guarded 
against by sealing the upper end of the fixture. 

d. No combination fixture in which the conductors are concealed in a 
space less than one-fourth inch between the inside pipe and the outside 
casing will be approved. 

e. Must be tested for " contacts " between conductors and fixture, for 
" short circuits," and for ground connections before it is connected to its 
supply conductors. , ., 

f. Ceiling blocks for fixtures should be made of insulating material ; if 
not the wires in passing through the plate must be surrounded with non- 
combustible non-absorptive, insulating material, such as glass or porcelain. 

g. Under no conditions shall there be a difference of potential of more 
than 300 volts between wires contained in or attached to the same fixture. 

•XI. Sockets. 

(For construction rules, see No. 55.) 

a. In rooms where inflammable gases may exist the incandescent lamp 
and socket must be inclosed in a vapor-tight globe, and supported on a pipe 
hanger, wired with approved rubber-covered wire (see No. 41) soldered 
directly to the circuit. 

b. In damp or wet places, or over specially inflammable stuff, waterproof 
sockets must be used. 

When waterproof sockets are used, they should be hung by separate 
stranded rubber-covered wires, not smaller than No. 14 B. & S., which 
should preferably be twisted together when the drop is over three feet. 
These wires should be soldered direct to the circuit wires, but supported 
independently of them. 

38. Flexible Cord — 

a. Must have an approved insulation and covering (see No. 45). 

b. Must not be used where the difference of potential between the two 
wires is over 300 volts. 

c. Must not be used as a support for clusters. 

d. Must not be used except for pendants, wiring of fixtures, and port- 
able lamps or motors. 

e. Must not be used in show windows. 

/. Must be protected by insulating bushings where the cord enters the 
socket. 

g. Must be so suspended that the entire weight of the socket and lamp 
will be born by knots under the bushing in the socket, and above the point 
where the cord comes through the ceiling-block or rosette, in order that 
the strain may be taken from the joints and binding screws. 

20. Arc Lig-ht* on XiOw-Potential Circuits — 

a. Must have a cutout (see No. 17a) for each lamp of each series of 
lamps. 

The branch conductors should have a carrying capacity about fifty per 
cent in excess of the normal current required by the lamp to provide for 
heavy current required when lamp is started or when carbons become stuck 
without overf using the wires. 

b. Must only be furnished with such resistances or regulators as are in- 
closed in non-combustible material, such resistances being treated as 
sources of heat. Incandescent lamps must not be used for resistance de- 
vices. 

c. Must be supplied with globes and protected by spark arresters and wire 
netting around globe, as in the case of arc lights on high-potential circuits 
(see Nos. 19 and 58). 



LOW POTENTIAL SYSTEMS. 775 

30. Economy Coils. 

a. Economy and compensator coils for arc lamps must be mounted on 
non-conbustible, non-absorptive insulating supports, such as glass or porce- 
lain, allowing an air space of at least one inch between frame and support, 
and in general to be treated like sources of heat. 

31. Decorative Series Eamps. 

a. Incandescent lamps run in series shall not be used for decorative pur- 
poses inside of buildings, except by special permission in writing from the 
Inspection Department having jurisdiction. 

33. Car- Wiring- — 

a. Must be always run out of reach of the passengers, and must have an 
approved rubber-insulating covering (see No. 41). 

33. Car-Houses — 

a. Must have the trolley wires securely suppoi'ted on insulating hangers. 
b Must have the trolley hangers placed at such distance apart that, in 
case of a break in the trolley wire, contact cannot be made with the floor. 

c. Must have cutout switch located at a proper place outside of the 
building, so that all trolley circuits in the building can be cut out at one 
point, and line circuit-breakers must be installed, so that when this cutout 
switch is open the trolley wire will be dead at all points within 100 feet of 
the building. The current must be cut out of the building whenever the 
same is not in use or the road not in operation. 

d. Must have all lamps and stationary motors installed in such a way 
that one main switch can control the whole of each installation — lighting 
or power — independently of main feeder-switch. No portable incandes- 
cent lamps or twin wire allowed, except that portable incandescent lamps 
may be used in the pits, connections to be made by tAvo approved rubber- 
covered flexible wires (see No. 41), properly protected against mechanical 
injury ; the circuit to be controlled by a switch placed outside of the pit. 

e. Must have all wiring and apparatus installed in accordance with rules 
under Class " C " for constant potential systems. 

/. Must not have any system of feeder distribution centering in the 
building. 

g. Must have the rails bonded at each joint with no less than No. 2 B. 
& S. annealed copper wire, also a supplementary wire to be run for each 
track. 

h. Must not have cars left with trolley in electrical connection with the 
trolley wire. 

34. lag-hting- and Power from Railway W^ires — 

a. Must not be permitted, under any pretense, in the same circuit with 
trolley wires with a ground return, except in electric railway cars, electric 
car houses and their power stations ; nor shall the same dynamo be used 
for both purposes. 

HltJH-POTESTIAI SYSTEMS. 

550 TO 3,500 Volts. 
Any circuit attached to any machine, or combination of machines, which de- 
velops a difference of' potential, between any two wires, of over 300 volts 
and less than 3,500 volts, shall be considered as a high-potential clr- 
tuit, and as coming under that class, unless an approved transforming 
device is used, which cuts the difference, of potential down to 30Q volts 
or less. 

35. Wires — 

(See also JVos. 14,15, and 16.) 

a. Must have an approved rubber-insulating covering (see No. 41). 

b. Must be always in plain sight and never incased, except where re- 
quired by the Inspection Department having jurisdiction 



776 NATIONAL ELECTRICAL COLE. 

c. Must be rigidly supported on glass or porcelain insulators, which raise 
the wire at least one inch from the surface wired over, and must he kept 
apart at least four inches for voltages up to 750 and at least eight inches for 
voltages over 750. 

Rigid supporting requires under ordinary conditions, where wiring along 
flat surfaces, supports at least about every four and one-half feet. If the 
wires are unusually liable to be disturbed, the distance between supports 
should be shortened. 

In buildings of mill construction, mains of Ko. 8 B. & S. wire or over, 
where not liable to be disturbed, may be separated about six inches for 
voltages up to 750 and about ten inches for voltages above 750 ; and run 
from timber to timber, not breaking around, and may be supported at each 
timber only. 

d. Must be protected on side walls from mechanical injury by a substan- 
tial boxing, retaining an air space of one inch around the conductors, 
closed at the top (the wires passing through bushed holes) and extending 
not less than seven feet from the floor. When crossing floor-timbers, in 
cellars or in rooms, where they might be exposed to injury, wires must be 
attached by their insulating supports to the under side of a wooden strip 
not less than one-half an inch in tbickness. 

30. Transformers (when permitted inside buildings, see No. 13) — 
{For construction rules, see No. 62.) 

a. Must be located at a point as near as possible to that at which the 
primary wires enter the building. 

b. Must be placed in an inclosure constructed of or lined with fire- 
resisting material : the inclosure to be used only for this purpose, and to be 
kept securely locked, and access to the same allowed only to responsible 
persons. 

c. Must be effectually insulated from the ground, and the inclosure i.> 
which they are placed must be practically air-tight, except that it shall be 
thoroughly ventilated to the outdoor air, if possible, through a chimney or 
flue. There should be at least six inches air space on all sides of the trans- 
former. 

31. Series Lamps. 

a. No system of multiple-series or series-multiple for light or power will 
be approved. 

b. Under no circumstances can lamps be attached to gas fixtures. 

EXTRA HIGH POTEHTIAI SYSTEMS. 

Over 3,500 Volts. 
Any circuit attached to any machine or combination of machines, which de- 
velops a difference of potential, between any two wires, of over 3,500 
volts, shall be considered as an extra high-potential circuit, and as 
coming under that class, unless an approved transforming device is 
used, which cuts the difference of potential down to 3,500 volts or less. 

3S. Primary Wires — 

a. Must not be brought into or over building, except power and sub- 
stations. 

39. Secondary Wires — 

a. Must be installed under rules for high-potential systems, when their 
immediate primary wires carry a current of over 3,500 volts, unless the 
primary wires are entirely underground, within city and village limits. 

The presence of wires carrying a current with a potential of over 3,500 
volts in the streets of cities,' towns, and villages is considered to increase 
the fire hazard. Extra high potential circuits are also objectionable in any 
location where telephone, telegraph, and similar circuits run in proximity 
to them. As the underwriters have no jurisdiction over streets and roads 
they can only take this indirect way of discouraging such systems ; but fur- 
ther, it is strongly urged that municipal authorities absolutely refuse to 
grant any franchise for right of way for overhead wires carrying a current 
of extra high potential through streets or roads which are used to any great 
extent for public travel or for trunk-line, telephone, or telegraph circuits. 



CLASS D. FITTINGS, MATERIALS, AND DETAILS. 



CIAIS ». riTTMTGi, MATERIALS, ASD RETAIJLS 

or cosrsivcTiosr. 

All Systems and Voltages. Insulated Wires — Rules 40 to 48. 
-tO, General Rules. 

a. Copper for insulated conductors must never vary in diameter so as to 
be more than two one- thousandths of an inch less than the specified size. 

b. Wires and cables of all kinds designed to meet the following specifica 
tions must be plainly tagged or marked as follows : 

1. The maximum voltage at which the wire is designed to be used. 

2. The words " National Electrical Code Standard." 

3. Name of the manufacturing company, and, if desired, trade-name of 

the wire. 

4. Month and year when manufactured. 

41. Rubber-Covered. 

a. Copper for conductors must be thoroughly tinned. 

Insulation for voltag*es between O and GOO. 

6. Must be of rubber or other approved substance, and be of a thickness 
not less than that given in the following table for B. & S. gauge sizes : 



rom 18 to 


16, inclusive, ^ 


" 14 to 


8, " g 3 4 


" 7 to 


2, " i'b 


" lto 


0000, " g v 


" 0000 to 


500,000, CM. ,JV 


" 500,000 to 


1,000,000, " B y 


Larger than 


1,000,000, " 4' 



Measurements of insulating wall are to be made at the thinnest portion 
of the dielectric. 

c. The completed coverings must show an insulation resistance of at 
least 100 megohms per mile during thirty days' immersion in water at 
seventy degrees Fahrenheit. 

d. Each foot of the completed covering must show a dieletric strength 
sufficient to resist throughout five minutes the application of an electro- 
motive force of 3,000 volts per one-sixty-fourth of an inch thickness of in- 
sulation under the following conditions : 

The source of alternating electro-motive force shall be a transformer of at 
least one kilowatt capacity. The application of the electro-motive force 
shall first be made at 4,000 volts for five minutes, and then the voltage in- 
creased by steps of not over 3,000 volts, each held for five minutes, until 
the rupture of the insulation occurs. The tests for dielectric strength shall 
be made on a sample of wire which has been immersed for seventy-two 
hours in water, one foot of which is submerged in a conducting liquid' held 
in a metal trough, one of the transformer terminals being connected to the 
wire and the other to the metal of the trough. 

Insulations for voltag-es between ©OO and 3,500: 

e. The thickness of the insulating walls must not be less than those given 
in the following table for B. & S. gauge sizes : 

From 14 to 1, inclusive, ^" 

From to 500,000, C. M., ft" covered by a tape or a braid. 

Larger than 500,000, C. M., &" covered by a tape or a braid 

/. The requirements as to insulation and break-down resistance for wires 
for low potential systems shall apply, with the exception that an insulation 
resistance of not less than 300 megohms per mile shall be required. 

g. Wire for arc-light circuits exceeding 3,500 volts potential shall have 
an insulating wall not less than six-thirty-seconds of an inch in thickness, 
and shall withstand a break-down test of at least 30,000 volts, and have an 
insulation of at least 500 megohms per mile. 

The tests on this wire to be made under the same conditions as for low- 
potential wires. 

Specifications for insulations for alternating currents exceeding 3,508 



778 NATIONAL ELECTRICAL CODE. 



volts h:ive been considered, but on account of tbe somewhat complex con- 
ditions in such work it has so far been deemed inexpedient to specify gen- 
eral insulations for this use. 

It. All of tbe above insulations must be protected by a substantial 
braided covering properly saturated with a preservative compound and suffi- 
ciently strong to w ltnstand all tbe abrasion likely to be met with in prac- 
tice, and sufficiently elastic to permit all wires smaller than No. 7 B. & S. 
gauge to be bent around a cylinder with twice tbe diameter of tbe wire, 
without injury to the braid. 

42. Slow -burning- Weatherproof. 

a. Tbe insulatioi shall consist of two coatings, the inner one to be fire- 
proof in character, the outer to be weatherproof. The inner fireproof coat- 
ing must comprise at least six-tenths of the total thickness of the wall. 
The completed covering must be of a thickness not less than that given in 
the following table for f3. & S. gauge sizes : 



rom 14 to 


8, inclusive, 


&" 


" 7 to 


o 


A" 


" 2 to 


0000,' 


5 // 


" 0000 to 


500,000, CM., 


i" 


" 500,000 to 


1,000,000, •• 


7 // 


arger than 


1,000,000, " 


r 



Measurements of insulating wall are to be made at the thinnest portion 
of the dielectric. 

b. The inner fireproof coating shall be layers of cotton or other thread, 
the outer one of which must be braided. All the interstices of these layers 
are to be filled with the fireproofing compound. This is to be material whose 
solid constituent is not susceptible to moisture, and which will not burn 
even when ground in an oxidizable oil, making a compound wbich, while 
proof against fire and moisture, at same time has considerable elasti- 
city, and which when dry will suffer no change at a temperature of 250 
degrees Fahrenheit, and which will not burn at even higher temperature. 

c. The weatherproof coating shall be a stout braid thoroughly satu- 
rated with a dense moistureproof compound thoroughly slicked down, 
applied in such manner as to drive any atmospheric moisture from the 
cotton braiding, thereby securing a covering to a greater degree waterproof 
and of high insulating power. This compound to retain its elasticity at 
zero Fahrenheit, and not to drip at 160 degrees Fahrenheit. 

This wire is not as burnable as the old " weatherproof," nor as subject to 
softening under heat, but still is able to repel the ordinary amount of 
moisture found indoors. It would not usually be used for outside work. 

43. SloH-l)uriiin»-. 

a. Tbe insulation shall be the same as the " slow-burning weatherproof," 
except that the outer braiding shall be impregnated with a fireproofing 
compound similar to that required for the interior layers, and with the 
outer surface finished smooth and hard. 

This " slow-burning " wire shall only be used with special permission of 
the Inspection Department having jurisdiction. 

This is practically the old •• Underwriters' " insulation. It is specially 
useful in hot, dry places where ordinary insulations would perish, also 
where wires are bunched, as on the back of a large switchboard or in a 
wire tower so that the accumulation of rubber or weatherproof insulation 
would result in an objectionably large mass of highly inflammable material. 

Its use is restricted, as its insulating qualities are'not high and are dam- 
aged by moisture. 

44. Weatherproof. 

a. The insulating covering shall consist of at least three braids thoroughly 
impregnated with a dense moisture repellent, which will not drip at a tem- 
perature lower than 180 degrees Fahrenheit. The thickness of insulation 
shall be not less than that of "slow-burning weatherproof." The outer 
surface shall be thoroughly slicked down." 

This wire is for outdoor use where moisture is certain and where fireproof 
qualities are not necessary. 



CLASS D. FITTINGS, MATERIALS, AND DETAILS. 779 

45. flexible Cord - 

a. Must be made of stranded copper conductors, each strand to be not 
larger than No. 26 or smaller than JSo. 30 B. & S. gauge, and each stranded 
conductor must be covered Dy an approved insulation and protected from 
mechanical injury by a tough braided outer covering. 

For pendent lamps: 

In this class is to be included all flexible cord which under usual condi- 
tions hangs freely in air, and which is not likely to be moved sufficiently to 
come in contact with surrounding objects. 

6. Each, stranded conductor must have a carrying capacity equivalent to 
not less than a No. 18 B. & S. gauge wire. 

c. The covering of each stranded conductor must be made up as follows : 

1. A tight, close wind of fine cotton. 

2. The insulation proper, which shall be either waterproof or slow- 

burning. 

3. An outer cover of silk or cotton. 

The wind of cotton tends to prevent a broken strand puncturing the insu- 
lation and causing a short circuit. It also keeps the rubber from corroding 
the coppei 

d. Waterproof insulation must be solid, at least one-thirty-second of an 
inch thick, and must show an insulation resistance of fifty megohms per 
mile throughout two weeks' immersion in water at 70 degrees Fahrenheit, 
and stand. the test prescribed for low-tension wires as far as they apply. 

e. Slow-burning insulation must be at least one-thirty-second of aii inch 
in thickness, and composed of substantial, elastic, slow-burning materials, 
which will suffer no damage at a temperature of 250 degrees Fahrenheit. 

/. The outer protecting braiding should be so put on and sealed in place 
that when cut it will not fray out, and where cotton is used, it should be 
impregnated with a flameproof paint, which will not have an injurious 
effect on the insulation. 

for portables: 

In this class is included all cord used on portable lamps, small portable 
motors, etc. 

g. Flexible cord for portable use must have waterproof insulation as 
required in section d for pendent cord, and in addition be provided with a 
reinforcing cover especially designed to withstand the abrasion it will be 
subject to in the uses to which it is to be put. 

For portable beating" apparatus: 

h. Must be made up as follows : — 

1. A tight, close wind of fine cotton. 

2. A thin layer of rubber about one-one-hundredth of an inch thick, or 

other cementing material. 

3. A layer of asbestos insulation at least three-sixty-fourths of an inch 

thick. 

4. A stout braid of cotton. 

5. An outer reinforcing cover especially designed to withstand abrasion. 
This cord is in no sense waterproof, the thin layer of rubber being speci- 
fied in order that it may serve merely as a seal to help hold in place the fine 
cotton and asbestos, and it should be so put on as to accomplish this. 

46. fixture Wire — 

a. Must have a solid insulation, with a slow-burning, tough, outer cover- 
ing, the whole to be at one-thirty-second of an inch in thickness, and show 
an insulation resistance between conductors, and between either conductor 
and the ground, of at least one megohm per mile, after one week's submer- 
sion in water at seventy degrees Fahrenheit, and after three minutes 
electrification with 550 volts. 

4?. Conduit Wire — 

Must complv with the following specifications : 

a. For metal conduits, having a lining of insulating material, single wires 



780 NATIONAL ELECTRICAL CODE. 

must comply with No. 41, and all duplex, twin, and concentric conductors 
must comply with No. 41, and must also have each conductor separately 
braided or taped and a substantial braid covering the whole. 

b. For unlined metal conduits, conductors must conform to the specifica- 
tions given for lined conduits, and in addition have a second outer fibrous 
covering at least one-thirty-second of an inch in thickness, and sufficiently 
tenacious to withstand the abrasion of being hauled through the metal 
conduit. 

The braid required around each conductor in duplex, twin, and concen- 
tric cables is to hold the rubber insulation in place and prevent jamming 
and flattening. 

48. Armored Caole. 

a. The armor of such cables must be at least equal in thickness and of 
equal strength to resist penetration by nails, etc., as the armor of metal 
covering of metal conduits (see No. 49 b). 

b. The conductors in same, single wire or twin conductors, must have an 
insulating covering as required by No. 41, any filler used to secure a round 
exterior must be impregnated with a moisture repellent, and the whole 
bunch of conductors and fillers must have a separate exterior covering of 
insulating material at least one-thirty-second of an inch in thickness, con- 
forming to the insulation standard given in No. 41, and covered with a sub- 
stantial braid. 

Very reliable insulation is specified, as such cables are liable to hard 
usage, and in part of their length may be subject to moisture, while they 
may not be easily removable, so that a breakdown of insulation is likely to 
be expensive. 

40. Interior Conduits. 

{For wiring rules, see Nos. 24 and 25.) 

a. Each length of conduit, whether insulated or uninsulated, must have 
the maker's name or initials stamped in the metal or attached thereto in a 
satisfactory manner, so that the inspectors can readily see the same. 

METAL CONDUITS WITH LINING OF INSULATING MATERIAL. 

b. The metal covering or pipe must be equal in strength to the ordinary 
commercial forms of gas-pipe of the same size, and its thickness must be not 
less than that of standard gas-pipe, as shown by the following table : 



Size. 
Inches. 


Thickness of 
Wall— Inches. 


Size. 
Inches. 


Thickness of 
Wall — Inches. 


\ 

% 
1 
. 1 


.109 

.111 

.113 

-.134 


1 

2 


.140 
.145 
.154 



An allowance of two one-hundredths of an inch for variation in manu- 
facturing and loss of thickness by cleaning will be permitted. 

c. Must not be seriously affected externally by burning out a wire inside 
the tube when the iron pipe is connected to one side of the circuit. 

d. Must have the insulating lining firmly secured to the pipe. 

e. The insulating lining must not crack or break when a length of the 
conduit is uniformly bent at temperature of 212 degrees Fahrenheit to an 
angle of ninety degrees, with a curve having a radius of fifteen inches, for 
pipes of one inch and less, and fifteen times the diameter of pipe for larger 
pipes. 

/. The insulating lining must not soften injuriously at a temperature 
below 212 degrees Fahrenheit, and must leave water in which it is boiled 
practically neutral. 

<r/. The insulating lining must be at least one-thirty-second of an inch in 
thickness ; and the materials of which it is composed must be of such a 
nature as will not have a deteriorating effect on the insulation of the con- 
ductor, and be sufficiently tough and tenacious to withstand the abrasion 
test of drawing long lengths of conductors ill and out of same. 









CLASS D. FITTINGS, MATERIALS, AND DETAILS. 781 



h. The insulating lining must not be mechanically weak after three days' 
submersion in water, and when removed from the pipe entire must not 
absorb more than ten per cent of its weight of water during 100 hours of 
submersion. 

i. All elbows or bends must be so made that the conduit or lining of same 
will not be injured. The radius of the curve of the inner edge of any elbow 
not to be less than three and one-half inches. Must have not more than tbe 
equivalent of four quarter bends from outlet to outlet, the bends at the 
outlets not being counted. 

UNLINED METAL CONDUITS. 

j. Plain iron or steel pipes of equal thickness and strengths specified for 
lined conduits in No. 49 b may be used as conduits, provided their interior 
surfaces are smooth and free from burs ; pipe to be galvanized, or the 
interior surfaces coated or enameled, to prevent oxidation, with some sub- 
stance which will not soften so as to become sticky and prevent wire from 
being withdrawn from the pipe. 

k. All elbows or bends must be so made that the conduit will not be 
injured. The radius of the curve of the inner edge of any elbow not to be 
less than three and one-half inches. Must have not more than the equiva- 
lent of four quarter bends from outlet to outlet, the bends at the outlet not 
being counted. 

5©. Wooden Moldings — 

{For wiring rules, see No. 24.) 

a. Must have, both outside and inside, at least two coats of waterproof 
paint, or be impregnated with a moisture repellent. 

b. Must be made of two pieces, a backing and cappiug, so constructed as 
to thoroughly incase the wire, and provide a one-half inch tongue between 
the conductors, and a solid backing, which, under grooves, shall not be less 
than three-eighths of an inch in thickness, and must afford suitable protec- 
tion from abrasion. 

It is recommended that only hardAvood molding be used. 

51. Switches — 

{See Nos. 17 and 22.) 

a. Must be mounted on non-combustible, non-absorptive, insulating bases, 
such as slate or porcelain. 

b. Must have carrying capacity sufficient to prevent undue heating, 

c. Must, when used for service switches, indicate, on inspection, whether 
the current be " on " or " off." 

d. Must be plainly marked, where it will always be visible, with the name 
of the maker and the current and voltage for which the switch is designed. 

e. Must, for constant potential systems, operate successfully at fifty per 
cent overload in amperes, with twenty-five per cent excess voltage under 
the most severe conditions they are liable to meet with in practice. 

/. Must, for constant potential systems, have a firm and secure contact ; 
must make and break readily, and not stop when motion has once been 
imparted by the handle. 

g. Must, for constant current systems, close the main circuit and discon- 
nect the branch wires when turned" off " ; must be so constructed that they 
shall be automatic in action, not stopping between points when started, and 
must prevent an arc between the points under all circumstances. They 
must indicate, upon inspection, whether the currents be " on " or " off." 

52. Cutouts and Circuit-Breakers — 

{For installation rules, see Nos. 17 and. 21.) 

a. Must be supported on bases of non-combustible, non-absorptive insu- 
lating material. 

b. Cutouts must be provided with covers, when not arranged in approved 
cabinets, so as to obviate any danger of the melted fuse metal coming in 
contact with any substance which might be ignited thereby. 



'82 NATIONAL ELECTRICAL CODE. 



c. Cutouts must operate successfully, under the most severe conditions 
they are liable to meet with in practice, on short circuits with fuses rated at 
fifty per cent above, and with a voltage twenty-five per cent above the 
current and voltage for which they are designed. 

d. Circuit-breakers must operate successfully, under the most severe 
conditions they are liable to meet with in practice, on short circuits when 
set at fifty per cent above the current, and with a voltage twenty-five per 
cent above that for which they are designed. 

e. Must be plainly marked, where it will always be visible, with the 
name of the maker, and current and voltage for which the device is de- 
signed. 

53. fuses — 

{For installation rules, see Nos. 17 and 21.) 

a. Must have contact surfaces or tips of harder metal having perfect 
electrical connection with the fusible part of the strip. 

b. Must be stamped with about eighty per cent of the maximum current 
they can carry indefinitely, thus allowing about twenty-five per cent over- 
load before fuse melts. 

With naked open fuses, of ordinary shapes and not over 500 amperes 
capacity, the maximum current which will melt them in about five minutes 
may be safely taken as the melting point, as the fuse practically reaches its 
maximum temperature in this time. With larger fuses a longer time is 
necessary. 

Inclosed fuses where the fuse is often in contact with substances having 
good conductivity to heat and often of considerable volnme, require a 
much longer time to reach a maximum temperature, on account of the 
surrounding material which heats up slowly. 

These data are given to facilitate testing. 

c. Fuse terminals must be stamped with the maker's name, initials, or 
some known trade-mark. 

5»-ft. Cutout Cauiuets — 

a. Must be so constructed, and cutouts so arranged, as to obviate any 
danger of the melted fuse metal coming in contact with any substance 
which might be ignited thereby. 

A suitable box can be made of marble, slate, or wood, strongly put 
together, the door to close against a rabbet so as to be perfectly dust-tight ; 
and it should be hung on strong hinges, and held closed by a strong hook or 
catch. If the box is wood, the inside should be lined with sheets of asbestos 
board about one-sixteenth of an inch in thickness, neatly put on, and 
firmly secured in place by shellac and tacks. The wire should enter 
through holes bushed with porcelain bushings ; the bushings tightly fitting 
the holes in the box, and the wires tightly fitting the bushings (using 
tape to build up the wire, if necessary) so as to keep out the dust. 

a»5. Sockets. 

{See No. 27.) 

Sockets of all kinds, including wall receptacles, must be constructed in 
accordance with the following specifications : — 

a. Standard Size.s. — The standard lamp socket shall be suitable for 
tise on any voltage not exceeding 250 and with any size lamp up to fifty 
candle-power. For lamps larger than fifty candle-power a standard keyless 
socket may be used ; or if a key is required, a special socket designed for 
the current to be used must be made. Any special sockets must follow the 
general spirit of these specifications. 

b. Marking. — The standard socket must be plainly marked fifty candle- 
power, 250 volts, and with either the manufacturer's name or registered 
trademark. Special large sockets must be marked with the current and 
voltage for which they are designed. 

c. Shell. — Metal used for shells must be moderately hard, but not 
hard enough to be brittle or so soft as to be easily dented or knocked out of 
place. Brass shells must be at least 0.013 inch in thickness, and shells of 
any other material must be thick enough to give the same stiffness and 
strength as brass. 



CLASS D. FITTINGS, MATERIALS, AND DETAILS. 783 

d. Lining. — The inside of the shells must he lined with insulating 
material, which shall absolutely prevent the shell from becoming a part 
of the circuit, even though the wires inside the socket should start from 
their position under binding screws. 

The material used for lining must be at least one thirty-second of an 
inch in thickness, and must be tough and tenacious. It must not be in- 
juriously affected by the heat from the largest lamp permitted in the 
socket, and must leave the water in which it is boiled practically neutral. 
It must be so firmly secured to the shell that it will not fall out with 
ordinary handling of the socket. It is preferable to have the lining in one 
piece. 

e. Cap. — Caps when of sheet brass must be at least 0.013 inch in thick- 
ness, and when cast or made of other metals must be of equivalent 
strength. The inlet piece, except for special sockets, must be tapped and 
threaded for ordinary one-eighth-inch pipe. It must contain sufficient metal 
for a full strong thread, and, when not of the same piece as the cap, must 
be joined to it in a way to give the strength of a single piece. 

There must be sufficient room in the cap to enable the ordinary wireman 
to easily and quickly make a knot in the cord, and push it into place in cap 
without crowding. All parts of the cap upon which tbe knot is likely to 
bear must be smooth and well insulated. 

/'. Frame and Screws. — The frame holding moving parts must be 
sufficiently heavy to give ample strength and stiffness. 

Brass pieces containing screw threads must be at least 0.06 of an inch in 
thickness. 

Binding-post screws must not be smaller than No. 5 wire and about forty 
threads per incn. 

g. Spacing. —Points of opposite polarity must everywhere be kept 
not less than three sixty-fourths of an inch apart unless separated by a 
reliable insulation. 

h. Connections. —The connecting points for the flexible cord must be 
made to very securely grip a No. 16 or 18 B. & S. conductor. A turned-up 
lug, arranged so that the cord may be gripped between the screw and the 
lug in such a way that it cannot possibly come out, is strongly advised. 

i. Lamp-Holder. — The socket must firmly hold the lamp in place so 
that it cannot be easily jarred out, and must provide a contact good enough 
to prevent undue heating with maximum current allowed. The holding- 
pieces, springs and the like, if a part of the circuit, must not be sufficiently 
exposed to allow them to be brought in contact with anything outside of 
lamp and socket. 

.;. Base. — The inside parts of the socket, which are of insulating 
material, except the lining, must be made of porcelain. 

k. Key. — The socket key-handle must be of such a material that it will 
not soften from the heat of a fifty candle-power lamp hanging downwards 
in air at seventy degrees Fahrenheit from the socket, and must be securely, 
but not necessarily rigidly, attached to the metal spindle it is designed to 
turn. 

/. Sealing. — All screws in porcelain pieces, which can be firmly sealed 
in place, must be so sealed by a waterproof compound which will not melt 
below 200 degrees Fahrenheit. 

to. Putting Together. — The socket must, as a whole, be so put 
together that it will not rattle to pieces. Bayonet joints or equivalent are 
recommended. 

n. Test. —The socket when slowly turned "on and off," at the rate of 
about two or three times per minute, must " make and break " the circuit 
6,000 times before failing, when carrying a load of one ampere at 220 volts. 

o. Keyless Sockets. — Keyless sockets of all kinds must comply with 
requirements for key sockets as far as they apply. 

p. Sockets of Insulating Materials.— Sockets made of porcelain 
or other insulating material must conform to the above requirements as 
far as they apply, and all parts must be strong enough to withstand a 
moderate amount of hard usage without breaking. 

q. Inlet Bushing. — When the socket is not attached to fixtures the 
threaded inlet must be provided with a strong insulating bushing, having a 
smooth hole of at least fifteen sixty-fourths of an inch in diameter. The 
corners of the bushing must be rounded, and all inside fins removed, so that 
in no place will the cord be subjected to the cutting or wearing action of a 
sharp edge. 



'84 NATIONAL ELECTRICAL CODE. 



56. Hanger-boards. 

a. Hanger-boards must be so constructed that all wires and current- 
carrying devices thereon shall be exposed to view, and thoroughly insu- 
lated by being mounted on a non-combustible, non-absorptive insulating 
substance. All switches attached to the same must be so constructed that 
they shall be automatic in their action, cutting off both poles to the lamp, 
not stopping between points when started, and preventing an arc betwean 
points under all circumstances. 

57. Arc JLamps. 

(For installation rules, see No. 19.) 

a. Must be provided with reliable stops to prevent carbons from falling 
out in case the clamps become loose. 

b. Must be carefully insulated from the circuit in all their exposed 
parts. 

c. Must, for constant-current systems, be provided with an approved 
hand switch, also an automatic switch that will shunt the current around 
the carbons, should they fail to feed properly. 

The hand switch to be approved, if placed anywhere except on the lamp 
itself, must comply with requirements for switches on hanger-boards as 
laid down in No. 56. 

58. Spark Arresters. 

{See No. 19 c.) 

a. Spark arresters must so close the upper orifice of the globe that it 
will be impossible for any sparks thrown off by the carbons to escape. 

50. Insulating- Joints - 

(See No. 26 a.) 

a. Must be entirely made of material that will resist the action of illumi- 
nating gases, and will not give way or soften under the heat of an ordinary 
gas-flame, or leak under a moderate pressure. They shall be so arranged 
that a deposit of moisture will not destroy the insulating effect, and shall 
have an insulating resistance of at least 250,000 ohms between the gas-pipe 
attachments, and be sufficiently strong to resist the strain they will be 
liable to be subjected to in being installed. 




Insulating Joint for Gas Pipes. 

b. Insulating joints having soft rubber in their construction will not be 
approved. 

OO. Resistance Boxes and Equalizers — 

(For installation rules, see No. 4.) 

a. Must be equipped with metal or with other non-combustible frames. 
The word " frame " in this section relates to the entire case and sur- 
roundings of the rheostat, and not alone to the upholding supports, 



! 



CLASS D. FITTINGS, MATERIALS, AND DETAILS. 785 

©1. Reactive Coils and Condensers. 

a. Reactive coils must be made of non-combustible material, mounted 
on non-combustible bases, and treated, in general, like sources of beat. 

b. Condensers must be treated like apparatus operating witb equivalent 
voltage and currents. Tbey must have non-combustible cases and supports, 
and must be isolated from all combustible materials, and, in general, 
treated like sources of beat. 

©2. Transformers — 

{For installation rules, see Nos. 11, 13, and 33.) 

a. Must not be placed in any but metallic or other non-combustible cases. 

b. Must be constructed to comply with the following tests : 

1. Shall be run for eight consecutive hours at a full load in watts 
under conditions of service, and at the end of that time the rise in 
temperature, as measured by the increase of resistance of the 
primary coil, shall not exceed 135 degrees Fahrenheit. 

2. The insulation of transformers when heated shall withstand con- 
tinuously for five minutes a difference of potential of 10,000 volts 
(alternating) between primary and secondary coils and core, and 
between the primary coils and core and a no-load " run " at double 
voltage for thirty minutes. 

©3. Xiig-litning- Arresters. 

{For installation rules, see No. 5.) 

a. Must be mounted on non-combustible bases, and must be so con- 
structed as not to maintain an arc after the discharge has passed, and must 
have no moving parts. 

CJLASS E.-MISCELIAafEOl§. 

©4. Sig-naling- Systems (governing wiring for telephone, telegraph, 
district messenger, and call-bell circuits, fire and burglar alarms, and all 
similar systems) — 

a. Outside wires should be run in underground ducts or strung on poles 
and, as far as possible, kept off of buildings, and must not be placed on the 
same cross-arm with electric light or power wires. 

b. When outside wires are run on same pole with electric light or power 
wires, the distance between the two inside pins of each cross-arm must not 
be less than twenty-six inches. 

c. All aerial conductors and underground conductors which are directly 
connected to aerial wires must be provided with some approved protective 
device, which shall be located as near their point of entrance to the build- 
ing as possible, and not less than six inches from curtains or other inflam- 
mable material. 

d. If the protector is placed inside of building, wires, from outside sup- 
ports to binding-posts of protector, shall comply with the following require- 
ments : 

1. Must be of copper, and not smaller than No. 16 B. & S. gauge. 

2. Must have an approved, rubber insulating covering (see No. 41). 

3. Must have drip loops in each wire immediately outside the building. 

4. Must enter buildings through separate holes sloping upward from the 

outside ; when practicable, holes to be bushed with non-absorptive, 
non-combustible insulating tubes extending through their entire 
length. Where tubing is not practicable, the wires shall be wrapped 
with two layers of insulating tape. 

5. Must be supported on porcelain insulators, so that they will not come 

in contact with anything other than their designed supports. 

6. A separation between wires of at least two and one-half inches must 

be maintained. 
In case of crosses these wires may become a part of a high-voltage circuit, 
so that similar care to that given high-voltage circuits is needed in placing 
them. Reliable porcelain bushings at the entrance holes are desirable, and 
are only waved under adverse conditions, because the state of the art in 
this type of wiring makes an absolute requirement inadvisable, 



786 NATIONAL ELECTRICAL CODE. 






e. The ground wire of the protective device shall be run in accordance 
with the following requii ements : 

1. Shall be of copper, and not smaller than No. 16 B. & S. 

2. Must have an approved rubber insulating covering (See No. 41). 

3. Shall run in as straight a line as possible to a good permanent 

ground, to be made by connecting to water- or gas-pipe, preferably 
water-pipe. If gas-pipe is used, the connection, in all cases, must 
be made between the meter and service pipes. In the absence of 
other good ground, the ground shall be made by means of a metallic 
plate or bunch of wires buried in permanently moist earth. 

4. Shall be kept at least three inches from all other conductors, and sup- 

ported on porcelain insulators so as not to come in contact with 

anything other than its designated supports. 

In attaching a ground wire to a pipe, it is often difficult to make a 

thoroughly reliable solder joint. It is better, therefore, where possible, to 

carefully solder the wire to a brass plug, which may then be firmly screwed 

into a pipe fitting. 

Where such joints are made under ground, they should be thoroughly 
painted and taped to prevent corrosion. 

f. The protector to be approved must comply with the following require- 
ments : 

1. Must be mounted on non-combustible, non-absorptive insulating 

bases, so designed that when the protector is in place, all parts 
which may be alive will be thoroughly insulated from the wall 
holding the protector. 

2. Must have the following parts : 

A lightning arrester which will operate with a difference of potential 
between wires of not over 500 volts, and so arranged that the 
chance of accidental grounding is reduced to a minimum. 

A fuse designed to open the circuit in case the wires become crossed 
with light or power circuits. The fuse must be able to open the 
circuit without arcing or serious flashing when crossed with any 
ordinary commercial light or power circuit. 

A heat coil which will operate before a sneak current can damage the 
instrument the protector is guarding. 

The heat coil is designed to Avarm up and melt out with a current 
large enough to endanger the instruments if continued for a long 
time, but so small that it would not blow the fuses ordinarily found 
necessary for such instruments. These smaller currents are often 
called " sneak " currents. 

3. The fuses must be so placed as to protect the arrester and heat coils, 

and the protector terminals must be plainly marked "line," "in- 
strument," " ground." 

g. Wires beyond the protector, except where bunched, must be neatly 
arranged and securely fastened in place in any convenient, workmanlike 
manner. They must not come nearer than six inches to any electric light 
or power wire in the building, unless incased in approved tubing so secured 
as to prevent its slipping out of place. 

The wires would ordinarily be insulated, but the kind of insulation is not 
specified, as the protector is relied upon to stop all dangerous currents. 
Porcelain tubing or circular loom conduit may be used for incasing wires 
where required as above. 

h. Wires connected with outside circuits, where bunched together within 
any building, or inside wires, where laid in conduits or ducts, with electric 
light or power wires, must have fire-resisting coverings, or else must be 
inclosed in an air-tight tube or duct. 

It is feared that if a burnable insulation were used, a chance spark might 
ignite it and cause a serious fire, for many installations contain a large 
amount of very readily burnable matter. 

<».». Electric CJas Eig-liting-. 

Where electric gas lighting is to be used on the same fixture with the 
electric light : 

a. No part of the gas-piping or fixture shall be in electric connection with 
the gas-lighting circuit, 



CLASS E. MISCELLANEOUS. 787 



b. The wires used with the fixtures must have a non-inflammable insula- 
tion, or, where concealed between the pipe and shell of the fixture, the 
insulation must be such as required for fixture wiring for the electric light. 

c. The whole installation must test free from " grounds." 

d. The two installations must test perfectly free from connection with 
each other. 

06. Insulation Resistance. 

The wiring in any building must test free from grounds ; i. e., the com- 
plete installation must have an insulation between conductors and between 
all conductors and the ground (not including attachments, sockets, recep-. 
tacles, etc.) of not less than the following : 

Up to 5 amperes 4,000,000 ohms. 

10 " 2,000,000 

" 25 " 800,000 

50 " 400,000 

100 " 200,000 

200 " 100,000 

400 " 25,000 

" 800 " 25,000 

" 1,600 " 12,500 

All cutouts and safety devices in place in the above. 

Where lamp sockets, receptacles, and electroliers, etc., are connected, 
one-half of the above will be required. 

07. Soldering- Fluid. 

a. The following formula for soldering fluid is suggested : 

Saturated solution of zinc chloride 5 parts 

Alcohol 4 parts 

Glycerine 1 part 



CLASS F. — MAJEURE WOJEKK. 
OS. Generators — 

a. Must be located in a dry place. 

b. Must have their frames insulated from their bed-plates. 

c. Must each be provided with a waterproof cover. 

d. Must each be provided with a name-plate, giving the maker's name, 
the capacity in voltage and amperes and normal speed in revolutions per 
minute — 

©9. Wires — 

a. Must have an approved insulating covering. 

The insulation for all conductors, except for portables, to be approved, 
must be at least one-eighth-inch in thickness and be covered with a substan- 
tial waterproof and flameproof braid. The physical characteristics shall 
not be affected by any change in temperature up to 200 degrees Fahrenheit. 
After two weeks' submersion in salt water at seventy degrees Fahrenheit it 
must show an insulation resistance of one megohm per mile after three 
minutes' electrification, with 550 volts. 

b. Must have no single wire larger than No. 12 B. & S. Wires to be 
stranded when greater carrying capacity is required. No single solid wire 
smaller than No. 14 B. & S., except in fixture wiring, to be used. 

Stranded wires must be soldered before being fastened under clamps or 
binding screws, and when they have a conductivity greater than No. 10 
B. & S. copper wire they must be soldered into lugs. 

c. Must be supported in approved molding, except at switchboards and 
portables. 

Special permission may be given for deviation from this rule in dynamo- 
rooms. 

d. Must be bushed with hard-rubber tubing one-eighth of an inch in 
thickness when passing through beams and non- water-tight bulkheads. 



788 



NATIONAL ELECTRICAL CODE. 



e. Must have, when passing through water-tight bulkheads and through 
all decks, a metallic stuffing-tube lined with hard rubber. In case of deck 
tubes they shall be boxed near deck to prevent mechanical injury. 

f. Splices or taps in conductors must be avoided as far as possible. Where 
it is necessary to make them they must be so spliced or joined as to be both 
mechanically and electrically secure without solder. They must then be 
soldered, to insure preservation, covered with an insulating compound equal 
to the insulation of the wire, and further protected by a waterproof tape. 
The joint must then be coated or painted with a waterproof compound. 

lO. Portable Conductors — 

a. Must be made of two stranded conductors, each having a carrying 
capacity equivalent to not less than ]S T o. 14 B. & S. wire, and each covered 
with an approved insulation and covering. 

Where not exposed to moisture or severe mechanical injury, each stranded 
conductor must have a solid insulation at leas! one-thirty-second of an inch 
in thickness, and must show an insulation resistance between conductors, 
and between either conductor and the ground, of at least one megohm per 
mile after one week's submersion in water at seventy degrees Fahrenheit 
and after three minutes' electrification, with 590 volts, and be protected by 
a slow-burning, tough-braided outer covering, 

Where exposed to moisture and mechanical injury — a? for use on decks, 
holds, and tire-rooms — each stranded conductor shall have a solid insula- 
tion to be approved, of at least one-thirty-second of an inch in thickness 
and protected by a tough braid. The two conductors shall then be stranded 
together, using a jute filling. The whole shall then be covered with a layer 
of flax, either woven or braided, at least one-thirty-second of an inch in 
thickness, and treated with a non-inflammable waterproof compound. 
After one week's submersion in water at seventy degrees Fahrenheit, at 550 
volts and a three minutes' electrification, must show an insulation between 
the two conductors, or between either conductor and the ground, of one 
megohm per mile. 

*1. Bell or Other Wires — 

a. Shall never run in same duct with lightning or power wires. 

H'i. Table of Capacity of Wires. 



B. &S. G. 


Area Actual 
CM. 


No. of 
Strands. 


Size of Strands 
B. & S. G. 


Amperes. 


19 


1,288 








18 


1,624 






'3 


17 


2,048 








16 


2,583 






'6 


15 


3,257 








14 


4,107 






12 


12 


6,530 






17 




9,016 


7 


19 


21 






11,368 


7 


18 


25 






14,336 


7 


17 


30 






18,081 


7 


16 


35 






22,799 


7 


15 


40 






30,856 


19 


18 


50 






38,912 


19 


17 


60 






49,077 


19 


16 


70 






60,088 


37 


18 


85 






75,776 


37 


17 


100 






99,064 


61 


18 


120 






124,928 


61 


17 


145 






157,563 


61 


16 


170 






198,677 


61 


15 


200 






250,527 


61 


14 


235 






296,387 


91 


15 


270 






373,737 


91 


14 


320 






413,639 


127 


15 


340 



CLASS F. MARINE WORK. 789 



When greater conducting area than that of a single wire is required, the 
conductor shall be stranded in a series of 1, Id, 3?, Ol, Ol, or 133, 
wires as may be required ; the strand consisting of one central wire, the 
remainder laid around it concentrically, each layer to be twisted in the 
opposite direction from the preceding 

*3. Switchboards — 

a. Must be made of non-combustible, non-absorbtive insulating material, 
such as marble or slate. 

b. Must be kept free from moisture, and must be located so as to bo 
accessible from all sides. 

c. Must have a main switch, main cutout, and ammeter for each gen- 
erator. 

Must also have a voltmeter and ground detector. 

d. Must have a cutout and switch for each side of each circuit leading 
from board. 

'J4-. Resistance Boxes — 

a. Must be made of non-combustible material. 

b. Must be located on switchboard or away from combustible material. 
When not placed on switchboard they must be mounted on non-inflam- 
mable, non-absorptive insulating material. 

c. Must be so constructed as to allow sufficient ventilation for the uses 
to which they are put. 

t&. Switches — 

a. Must have non-combustible, non-absorptive insulating bases. 

b. Must operate successfully at fifty per cent overload in amperes with 
twenty-five per cent excess voltage under the most severe conditions they 
are liable to meet with in practice, and must be plainly marked, where 
they will always be visible, with the name of the maker and the current 
and voltage for which the switch is designed. 

c Must be double pole when circuits which they control supply more 
than six sixteen-candle-power lamps or their equivalent. 

d. When exposed to dampness, they must be inclosed in a water-tight 
case. 

?G. Cutouts — 

a. Must have non-combustible, non-absorptive insulating bases. 

b. Must operate successfully, under the most severe conditions they are 
liable to meet with in practice, on short circuit with fuse rated at fifty per 
cent above, and with a voltage twenty-five per cent above the current and 
voltage they are designed for, and must be plainly marked, where they will 
always be visible, with the name of the maker and current and voltage for 
which the device is designed. 

c. Must be placed at every point where a change is made in the size of 
the wire (unless the cutout in the larger wire will protect the smaller). 

d. In places such as upper decks, holds, cargo spaces, and fire-rooms a 
water-tight and fireproof cutout may be used, connecting directly to mains 
when such cutout supplies circuits requiring not more than 660 watts 
energy. 

e. When placed anywhere except on switchboards and certain places, as 
cargo spaces, holds, fire-rooms, etc., where it is impossible to run from 
center of distribution, they shall be in a cabinet lined with fire-resisting 
material. 

/. Except for motors, searchlights, and diving-lamps shall be so placed 
that no group of lamps, requiring a current of more than six amperes, shall 
ultimately be dependent upon one cutout. 

A single-pole covered cutout may be placed in the molding when same con- 
tains conductor supplying circuits requiring not more than 220 watts energy. 

Hit. fixtures — 

a. Shall be mounted on blocks made from well-seasoned lumber treated 
with two coats of white lead or shellac. 

b. Where exposed to dampness, the lamp must be surrounded by a vapor- 
proof globe. 



790 NATIONAL ELECTRICAL CODE. 

c. Where exposed to mechanical injury the lamp must he surrounded 
hy a globe protected hy a stout wire guard. 

d. Shall he wired with same grade of insulation as portable conductors 
which are not exposed to moisture or mechanical injury. 

?S. Sockets. 

a. No portion of the lamp socket or lamp base exposed to contact with 
outside objects shall be allowed to come into electrical contact with either 
of the conductors. 

VO. Wooden Moulcliiig-s — 

a. Must be made of well-seasoned lumber and be treated inside and out 
with at least two coats of white lead or shellac. 

b. Must be made of two pieces, a backing and a capping, so constructed 
as to thoroughly incase the wire, and provide a one-half inch tongue 
between the conductors, and a solid backing which, under grooves, shall 
not be less than three-eighths of an inch in thickness. 

c. Where molding is run over rivets, beams, etc., a backing strip must 
first be put up and the molding secured to this. 

d. Capping must be secured by brass screws. 

SO. Jflotors — 

a. Must be wired under the same precautions as with a current of same 
volume and potential for lighting. The motor and resistance box must be 
protected by a double-pole cutout, and controlled by a double-pole switch, 
except in cases where one-quarter horse-power or less is used. 

The leads or branch circuits should be designed to carry a current at 
least fifty per cent greater than that required by the rated capacity of the 
motor to provide for the inevitable overloading of the motor at times. 

b. Must be thoroughly insulated. Where possible, should be set on base 
frames made from filled, hard, dry, wood, and raised above surrounding 
deck. On hoists and winches they shall be insulated from bed-plates by 
hard rubber, fiber, or similar insulating material. 

c. Shall be covered with a waterproof cover when not in use. 

d. Must each be provided with a name-plate giving maker's name, the 
capacity in volts and amperes, and the normal speed in revolutions per 
minute. 

^O'KaUL ftl'GCJEKTIOXft. 

In all electric work conductors, however well insulated, should always be 
treated as bare, to the end that under no conditions, existing or likely to 
exist, can a grounding or short circuit occur, and so that all leakage from 
conductor to conductor, or between conductor and ground, may be reduced 
to the minimum. 

In all wiring special attention must be paid to the mechanical execution 
of the work. Careful and neat running, connecting, soldering, taping of 
conductors and securing and attaching of fittings, are specially conducive 
to security and efficiency, and will be strongly insisted on. 

In laying out an installation, except for constant-current systems, the 
work should, if possible, be started from a center of distribution, and 
the switches and cutouts, controlling and connected with the several 
branches, be grouped together in a safe and easily accessible place, where 
they can be readily got at for attention or repairs. The load should be 
divided as evenly as possible among the branches, and all complicated and 
unnecessary wiring avoided. 

The use of wire-ways for rendering concealed wiring permanently acces- 
sible is most heartily indorsed and recommended ; and this method of 
accessible concealed construction is advised for general use. 

Architects are urged, when drawing plans and specifications, to make pro- 
vision for the channeling and pocketing of buildings for electric light or 
power wires, and in specifications for electric gas lighting to require a two- 
wire circuit, whether the building is to be wired for electric lighting or not, 
so that no part of the gas fixtures or gas-piping be allowed to be used for 
the gas-lighting circuit. 



FOUNDATIONS AND STRUCTURAL 
MATERIALS. 



rOWEJX iTATIOHf CO]¥STRUCTIO]¥. 

Chart. 

(By E. P. Roberts & Co.) 

("Foundation 
'< Setting 



Steam 
Plant 



Boilers 



Stack 



Water. 



Fuel 



1 Aii- 



Link y 



En- 
gines 



STA- j 
TION 



Elec- 
trical 
plant 



Build- 
ing 



( Source 

J Pumps and injectors, valves 
( | and gauges 
. < I Heaters 

i_ f Sediment f Blow off 

( Mud drum 
J ( Steam pipe and 

| J valve to heater 

1 Entrained water, 
l^Steam [_ separator 
f Placing in building 
. J Placing in boiler 

| Removal of coke and ashes 
^Removal of soot \ 
. . Supply to surface 
f Piping and valves 
J Coverings 
I Drains and drips 
^Supports 
'Foundation 
Steam to cylinder 
Oil to cylinder 
Steam from cylinder 
Water from cylinder 
Oil to engine 
Oil from engine 
Engine indicator 
^ ( Steam to condenser 
-i Water to condenser 
(^Water from condenser 
f Belts 
Connecting links ■ ■ ■ A Shafts 
^Pulleys 
^Foundation 
I Lubrication 
J Insulation 
] Governing devices 
j Measuring devices 
' Safety devices 
Dynamos to switchboard 
Switchboards to line 
Track to dynamo 
Distribution devices 
Dynamo governing devices 
Dynamo measuring devices 
Feeder to measuring devices 
| Safety devices 
■ v Cut-out and lightning arrester 
( Weatherproof 
| Fireproof 
■i Ventilated 

Light 
^Provisions for cranes or other strains foreign to its func- 
tions as a shelter. 
791 



Foundations 
Lubrication 



fDynamos 



Wire 



Switchboard 



'92 FOUNDATIONS AND STRUCTURAL MATERIALS. 



FOUNDATIONS. 

The term foundation designates the portion of a structure used as a base 
on which to erect the superstructure, and must be so solid that no move- 
ment of the superstructure can take place after its erection. 

As all foundations or structures of coarse masonry, whether of brick or 
stone, will settle to some extent, and as nearly all soils are compressible 
under heavy weight, care must be taken that the settlement be even all 
over the structure in order to avoid cracks or other flaws. Although it is 
quite general to make the excavation for all the sub-foundation without 
predetermining in more than a general way the nature of the subsoil, and 
then adapting the base of the foundation to the nature of soil found ; yet in 
large undertakings, where there may be question as to the bearing, borings 
are made and samples brought up in order to determine the different strata 
and distance of rock below the surface. Where foundations are not to be 
deep, or the soil is of good quality, a trench or pit is often sunk alongside 
the location of the proposed foundation, and the quality of the soil deter- 
mined in that way. 

foundations on Rock. 

The surface of rock should be cleaned and dressed, all decayed portions 
removed crevices filled with grouting or concrete, and where the surface 
is inclined it should be cut into a series of level steps before commencing 
the structure In such cases of irregular levels, all mortar joints must be 
kept as close as possible, iu order to prevent unequal settlement. A still 
better way is to bring all such uneven surfaces to a common level with a 
good thick bed of concrete, which, if properly made, will become as incom- 
pressible as stone or brick. 

The load on rock foundation should never exceed one-eighth its crushing- 
load. Baker says " the safe bearing power of rock is certainly not less than 
one-tenth of the ultimate crushing strength of cubes. That is to say, the 
safe bearing power of solid rock is not less than 18 tons per square foot for 
the softest rock, and 180 for the strongest. It is safe to say that almost any 
rock, from the hardness of granite to that of a soft crnmbling stone easily 
worn by exposure to the weather or to running water, when well bedded 
will bear the heaviest load that can be brought upon it by any masonry 
construction." Rankine gives the average of ordinary cases as 20,000 
pounds per square foot on rock foundations. Later in this chapter (page 
824) will be found a table that gives the crushing load in pounds per square 
inch for most of the substances used in foundations and building-walls. 

Foundations on Sand or Gravel. 

Strong gravel makes one of the best bottoms to build on; it is easily leveled, 
is almost incompressible, and is not affected by exposure to the atmosphere. 

Sand confined so that it cannot escape forms an excellent foundation, and 
is nearly incompressible. It has no cohesion, and great care must be used 
in preparing it for a foundation. Surface water must be kept from running 
into earth foundation beds, and the beds themselves must be well-drained 
and below frost-line. Baker says that a rather thick bed of sand or gravel, 
well protected from running water, will safely bear a load of 8 to 10 tons per 
square foot. Of course the area of the surface must be proportioned to the 
weight of the superstructure, and to the bearing resistance of the material, 
and for this reason it is common practice to spread the subfoundation to 
give it the proper area. Rankine gives 2,500 to 3,500 lbs. per square foot as 
the greatest allowable pressure on firm earths. 

Foundation on day. 

A good stiff clay makes a very good foundation bed, and will support 
great weight if care is taken in its preparation. Water must be kept away 
from it, and the foundation level must be below the frost-line. The less 
clay is exposed to the atmosphere the better will be the result. Baker 
gives as safe bearing power for clay 3,000 or 4,000 pounds per square foot. 
Gaudard says a stiff clay will support in safety 5,500 to 11,000 pounds per 
square foot, 



FOUNDATIONS. 793 

Foundation on Soft Earth. 

"Where the earth is too soft to support the superstructure, the trench is 
excavated to a considerable width, and to a considerable depth below the 
frost-line ; then a bed is prepared of stones, sand, or concrete, the latter 
being most in use to-day. In fact, it is a common thing to cover the whole 
area of the basement of large power stations with a heavy layer of concrete 
of a thickness sufficient to sustain not only the building-walls, but all nn> 
chine foundations. 

Sand makes a good foundation bed over soft earth, if the earth is of a 
quality that will retain the sand in position. Sand may be rammed in 
9-mch layers in a soft earth trench, or it can be used as piles instead of 
wooden ones, by boring holes 6 or 8 inches in diameter and say six feet deep 
and ramming the sand in wet. It is necessary to cover the surface with 
planking or concrete to prevent the earth pressing upward. Alluvial soils 
are considered by Baker safe under a load of one-half to one ton per square 

foundation on S*iS«»«, 

When the earth is unsuitable in nature to support foundations, it is com- 
mon to drive piles, on the tops of which the foundation is then built. 
When possible the piles are driven to bed rock, otherwise they are made of 
such length and used in such number as to support the superstructure by 
reason of the friction of their surfaces in the soil. Where the soil is quite 
soft it is also common to drive piles in large number all over the basement 
area in order to consolidate the earth, and make all parts of a better bearing 
quality. 

Piles must be driven and cut off below the water level, and a grillage of 
heavy timbers or a layer of broken stone and a capping of concrete must be 
placed on top of them for supporting the foundation. 

The woods most used for piles are spruce and hemlock in soft or medium- 
soft soils, or when they are to be always under water, hard pine, elm, and 
beech in firmer soils, and oak in compact soils. When piles are liable to be 
alternately wet and dry, white oak or yellow pine should be employed. 

Piles should not be less than 10 inches in diameter at the small end, nor 
more than 14 inches at the large end. They should be straight-grained, and 
have the bark removed. The point is frequently shod with an iron shoe, to 
prevent the pile from splitting, and the head is hooped with an iron band to 
prevent splitting or brooming. 

Safe Iioad on Piles. 

Rankine gives as safe loads on piles 1,000 pounds per square inch of head, 
if driven to firm ground; 200 pounds, if in soft earth, and supported by 
friction. 

Major Sanders, U. S. Engineers, gives the following rule for finding the 
safe load for a wooden pile driven until each blow drives it short and nearly 
equal distances : 

_, „ , , . , Weight of hammer in pounds X fall in inches 

Safe load in pounds = - — - : — =- , . — =- — = — r^-, 

8 X inches driven by last blow 

Trautwine's rule is as follows : 

3 VFall in feet x Lbs. wgt. of hammer x .023 



Extreme load in gross tons = 



inches driven by last blow -4- 1 



He recommends as safe load one-half the extreme load where driven in 
firm soils, and one-sixth when driven in soft earths or mud. The last blow 
should be delivered on solid wood, and not on the " broomed " head. 

Piles under Trinity Church, Boston, support two tons each. 

Piles under the bridge over the Missouri Biver at Bismarck, Dakota, were 
driven into sand to a depth of 32 feet, and each sustained a load of 20 tons. 

A pile under an elevator at Buffalo, N. Y., driven into the soil to a depth 
of 18 feet, sustained a load of 35 tons. 



94 FOUNDATIONS AND STRUCTURAL MATERIALS. 



Arrang-ement of Piles. 

Under Avails of a building piles are arranged in rows of two or three, 
spaced 24 inches or 30 inches on centers. Under piers or machine founda- 
tions they are arranged in groups, the distance apart being determined by 
the weight to be supported, but usually, as above, from two to three feet 
apart on centers. 

Concrete foundation Bed. 

As mentioned in a previous paragraph, concrete is now used to a very 
great extent for foundation beds, not only in soft earths, but to level up all 
kinds of foundation beds. 

Good proportions are by measure, using Portland cement: 

Cement, 1 part, 

Coarse sand, 2 parts, 

Broken stone, 5 parts. 

Only hard and sharp broken stone that will pass through a 1£- or 2-inch 
ring should be used ; and the ingredients should be thoroughly mixed dry, 
and after mixing, add just as little water a,s will fully wet the material- 
Concrete should be placed carefully. It is never at its best when dropped 
any distance into place. It should be thoroughly rammed in six- or nine- 
inch layers, and after setting the top of each layer should be cleaned, wet, 
and roughened before depositing another layer over it. It is common prac- 
tice to place side-boards in trenches and foundation excavations in order to 
save concrete. This is economical, but not good practice, if the earth is 
even moderately firm, as filling out the inequalities makes the foundation 
much firmer and steady in place. Weight of good concrete per cubic foot 
is 130 to 160 lbs. dry. 

.Permissible Loads on foundation Beds. 

Piles, in firm soil, each pile 30,000 to 140,000 lbs. 

Piles in made ground, each pile, 4,000 " 

Clay, 4,000 " 

Coarse gravel and sand, 2,500 to 3,500 " 

Rock foundations, average, 20,000 " 

Concrete, 8,000 " 
New York City laws, no pile to be 

weighted with a load exceeding, 40,000 " 
New York City rule for solid nat- 
ural earth per superficial foot, 8,000 " 

Concrete foundations. 

One of the best foundations for engines or other heavy machinery is con 
structed wholly of concrete, rammed in a mold of planking. The mould 
can be made of any desired shape; the holding-down bolts placed by tem- 
plate, and the material rammed in layers not exceeding 12 inches thick. 

Brick foundations. 

Only the best hard-burned brick should be used for foundations, and they 
should be thoroughly wet before laying. To insure a thorough wetting, the 
bricks should be deposited in a tub of water. Bricks should be push placed 
in a good rich cement mortar. Grouting should never be used, as it takes 
too long to dry. Joints should be very small. A well constructed brick 
foundation will break as easily in the brick as at the joints after it has been 
built for some time. 

Stone foundations. 

Rubble stone foundations should start with large flat stones on the bot- 
tom. Care must be taken that all are well bedded in mortar, and that the 
work is well tied together by headers, 



MORTARS. 795 

Dimension stone foundations are always laid out with the heavy and thick 
stones at the bottom, and gradually decreasing in height, layer by layer, to 
the top. A large cap-stone, or several if the size is too great for one, is 
often placed on top of the foundation. Care must be taken to bed each stone 
in cement mortar, so that the joints will be thin and yet leave all the spaces 
between the stones completely filled with mortar to prevent any unequal 
strains on the stone. In all large foundations use plenty of headers; and if 
the backing or center is of rubble, see that all stones are well bedded, and 
the crevices filled with spawls and cement. 

I-JBeam foundations. 

One of the best and now most common methods of constructing founda- 
tions for piers, walls, columns, etc., is the use of steel I-beams set in con- 
crete. Knowing the weight to be supported and the bearing value of the 
soil, excavation is made of the right dimensions to get the proper area of 
bearing, then I-beams of predetermined dimensions are laid parallel along 
the bottom, and held in place with bolts from one beam to the next. Con- 
crete is rammed in all the spaces to a level with the top of the beams. An- 
other similar layer of beams is then laid on top of the first, and at right 
angles thereto, and the spaces also filled with concrete. The column base, 
or footing course, is then set on the structure ready to receive the column. 

For method of calculation of dimensions of I-beams for use in foundations 
for piers and walls, the reader can consult the hand-book of the Carnegie 
Steel Company, and those of other Steel Companies. 

HORTAR8. 

lime Mortar. 

Good proportions are : 1 measure or part quicklime, 3 measures of sand, 
well mixed, or tempered with clean water. 

Quantity required. — Trautwine. 20 cu. ft. sand and 4 cu. ft. of 

lime, making about 22| cu. ft. mortar, will lay 1,000 bricks with average 
coarse joints. 

Weig-Iit. — 1 bbl. weighs 230 lbs. net, or 250 lbs. gross; 1 heaped bushel 
of lump lime weighs about 75 lbs.; 1 struck bushel ground quick lime, loose, 
weighs about 70 lbs. Average hardened mortar weighs about 105 to 115 lbs. 
per cu. ft. 

Tenacity. — Ordinary good lime mortar 6 months old has cohesive 
strength of from 15 to 30 lbs. per square inch. 

Adhesion to common bricks or rubble. — At 6 months old, 12 
to 24 lbs. per sq. inch. 

Cement Mortar. 

Good proportions are: 1 measure cement, 2 measures sand, i measure 
water. The above is rich and strong, and for ordinary Avork will allow in- 
crease of sand to 3 or 4 measures. 

Quantity required. — Trautwine. 1 bbl. cement, 2 bbls. sand, will 
lay 1 cu. yd. of bricks with § inch joints or 1 cu. yard rubble masonry. 

Weijsrnt. — 

American Rosendale, ground, loose, average, 56 lbs. per cu. ft. 

" " IT. S. struck bushel, 70 " " " " 

English Portland, 81 to 102 " " " " 

" " per struck bushel, 100 to 128 " " " " 

" " per bbl., 400 to 430 " " " " 



796 FOUNDATIONS AND STRUCTURAL MATERIALS. 



Average Strength of IVeat Cement after © Days in 
Water. 



Portland, artificial . . . 

" Saylor's natural 

U. S. common hydraulic . 



Tensile, Lbs. 
per sq. in. 



200 to 350 
170 to 370 
40 to 70 



Compress, Lbs, 
per sq. in. 



1400 to 2400 
1100 to 1700 
250 to 450 



Compress, 
Tons per sq. ft. 



90 to 154 
71 to 109 
16 to 29 



Cements are weakened by the addition of sand somewhat as shown in the 
following table : calling neat cement 1. 



Sand. 





i 


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6 


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Adhesion to US ricks or Rubble. 

Adhesion of cement, either neat or mixed with sand, will average about 
three-fourths the tensile strength of the mortar at the same age. 

SA9TD A\M CEMENT. 

Recommendations of Am. Soc. Civil Engineers. 

land. — To be crushed quartz only. To pass, 

1st sieve, 400 meshes per square inch. 

2d " 900 
Sand to pass the 400 mesh, but be caught by the 900 mesh, all finer parti- 
cles to be rejected. 

Portland Cenient. — For fineness, to pass, 
1st sieve, 2500 meshes per square inch. 
2d " 5476 " " " " 

3d " 10000 " " 

Should be stored in bulk for at least 21 days to air-slake and free it from 
lime, as lime swells the bulk, and if not removed is apt to crack the work. 



IRON A^» STEEL 

Iron, weig-nt of: cu. in. 

Cast, .2604 Lbs. 

Wrought, .2777 " 
a z= sectional area wrought-iron bar. 

x = weight per foot " " " 

3x _ 10a 

10 X -~5" 



a 



Steel, weig-nt of: 



cu. in. 

.2831 Lbs. 



cu. ft. 

450 Lbs. 



cu. ft. 

489.3 Lbs. 



Cast Iron. Test. 

Bar an inch square, supported on edges 1 foot apart, must sustain 1 ton at 
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1.237 


37.97 


29.82 


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30.94 


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130.2 


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1.728 


40.83 


32.07 


135.5 


106.4 


2.552 


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42.30 


33.23 


1 


140.8 


110.6 


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2.301 


f 


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34.40 


146.3 


114.9 


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3.333 


2.618 




45.33 


35.60 


I 


151.9 


119.3 


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3.763 


2.955 


\ 


46.88 


36.82 


I 


157.6 


123.7 


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4.219 


3.313 


13 


48.45 


38.05 


7 


163.3 


128.3 


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3.692 


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50.05 


39.31 


1 


169.2 


132.9 


5.208 


4.091 


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51.68 


40.59 


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175:2 


137.6 


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5.742 


4.510 


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53.33 


41.89 


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181.3 


142.4 


6.302 


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55.01 


43.21 


I 


187.5 


147.3 


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5.410 


1 


56.72 


44.55 




193.8 


152.2 


7.500 


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58.45 


45.91 


| 


200.2 


157.2 




8.138 


6.392 


i 


60.21 


47.29 


1 


206.7 


162.4 


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8.802 


6.913 


5 

T5 


61.99 


48.69 


8 


213.3 


167.6 


11 

¥ 


9.492 


7.455 


1 


63.80 


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1 


226.9 


178.2 


10.21 


8.018 




65.64 


51.55 


J 


240.8 


189.2 


13 


10.95 


8.601 


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67.50 


53.01 


3 


255.2 


200.4 


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11.72 


9.204 


9 


69.39 


54.50 


9 4 


270.0 


212.1 


15 


12.51 


9.828 


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71.30 


56.00 


■% 


285.2 


224.0 


2 16 


13.33 


10.47 


t 


73.24 


57.52 


h 


300.8 


236.3 


1 
f 


14.18 


11.14 


75.21 


59.07 


3 


316.9 


248.9 


15.05 


li;82 


13 


77.20 


60.63 


10 4 


333.3 


261.8 


f 


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12.53 


¥ 

15 
IB 
5 


79.22 


62.22 


} 


350.2 


275.1 


16.88 


13.25 


81.26 


63.82 


i 


367.5 


288.6 


5 


17.83 


14.00 


83.33 


65.45 


J 


385.2 


302.5 


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14.77 


! 


85.43 


67.10 


11 


403.3 


316.8 


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19.80 


15.55 


87.55 


68.76 


I 


421.9 


331.3 




20.83 


16.36 


16 


89.70 


70.45 


I 


440.8 


346.2 


I 


21.89 


17.19 


91.88 


72.16 


460.2 


361.4 


22.97 


18.04 


16 


94.08 


73.89 


12 


480. 


377. 



800 



FOUNDATIONS AND STRUCTURAL MATERIALS. 



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GAUGE FOR SHEET AND PLATE IBOX. 



801 



XJ. 8. STANDARD 6AUGE FOR IHEET 4\D 
PLATE IROX AID STEEL. 1S03. 





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11.90625 


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18.75 


8.505 


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201.82 


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7-16 


0.4375 


11.1125 


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17.50 


7.938 


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188.37 


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7.371 


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13.75 


6.237 


67.13 


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7.9375 


200 


12.50 


5.67 


61.03 


134.55 


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7.14375 


180 


11.25 


5.103 


54.93 


121.09 


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17-64 


0.265625 


6.746875 


170 


10.625 


4.819 


51.88 


114.37 


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1-4 


0.25 


6.35 


160 


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4.536 


48.82 


107.64 


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0.234375 


5.953125 


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9.375 


4.252 


45.77 


100.91 


5 


7-32 


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5.55625 


140 


8.75 


3.969 


42.72 


94.18 


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12-64 


0.203125 


5.159375 


130 


8.125 


3.685 


39.67 


87.45 


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3-16 


0.1875 


4.7625 


120 


7.5 


3.402 


36.62 


80.72 


8 


11-64 


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4.365625 


110 


6.875 


3.118 


33.57 


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6.25 


2.835 


30.52 


67.27 


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3.571875 


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5.625 


2.552 


27.46 


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2.268 


24.41 


53.82 


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1.984 


21.36 


47.09 


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3.75 


1.701 


18.31 


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1.417 


15.26 


33.64 


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1.276 


13.73 


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12.21 


26.91 


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0.7938 


8.544 


18.84 


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1.50 


0.6804 


7.324 


16.15 


21 


11-320 


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0.6237 


6.713 


14.80 


22 


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0.793750 


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0.567 


6.103 


13.46 


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802 FOUNDATIONS AND STRUCTURAL MATERIALS. 

COX/UM^S, PIIIARS, OH STRUTS. 
Hodg'kinson'i Formula for Columns, 

P = crushing weight in pounds ; d = exterior diameter in inches ; d x 
interior diameter in inches ; L = length in feet. 



Kind of Columns. 



Both ends rounded, the 
length of the column 
exceeding 15 times its 
diameter. 



Both ends flat, the 
length of the column 
exceeding 30 times its 
diameter. 



Solid cylindrical col- 
umns of cast iron . 



Hollow cylindrical 
columns of cast 



Solid cylindrical col- ) 
umns of wrought [ 
iron ) 

Solid square pillar of ) 
Dantzic oak (dry) . ] 



7' = 29,120 



P = 95,850 



d 3 -™ 

^3.76 _ ^3.76 



lA* 



P = 98,920 



P = 99,320 



P = 299, 



P = 24,540 



d s - 55 

f/3-55 _ ^3.55 



L™ 



d s - 55 
d* 



These formula} apply only to cases of breakage caused by bending rather 
than mere crushing. Where the column is short, or say five times its diam- 
eter in length, then the following formula applies. 
Let 

P zr value given in preceding formulae, 
K = transverse section of column in square inches, 
C= ultimate compressive resistance of the material, 
W — crushing strength of the column. 



Then 



W — 



PCX 



P + iCK 

Hodgkinson's experiments were made upon columns the longest of which 
for cast iron was 60£ inches, and for wrought iron 90f inches. 
The following are some of his conclusions : 

1. In all long pillars of the same dimensions, when the force is applied in 
the direction of the axis, the strength of one which has flat ends is about 
three times as great as one with rounded ends. 

2. The strength of a pillar with one end rounded and the other flat is an 
arithmetical mean between the two given in the preceding case of the same 
dimensions. 

3. The strength of a pillar having both ends firmly fixed is the same as 
one of half the length with both ends rounded. 

4. The strength of a pillar is not increased more than one-seventh by en- 
larging it at the middle. 

Gordon's formulae, deduced from Hodgkinson's experiments, are 
more generally used than Hodgkinson's own. They are : 

Columns with both ends fixed or flat P =. — — — r ', 



Columns with one end flat, the other end round, P = 



fS 



Columns with both ends round or hinged, P : 



fS 



STRENGTH OF MATERIALS. 80* 



S — area of cross-section in inches ; 
P = ultimate resistance of column in pounds ; 
f — crushing strength of the material in pounds per square inch ; 
. . „ Moment of inertia 

r = least radius of gyration, m inches, r 2 = — — ; 

area of section 
I = length of column in inches ; 
a — a coefficient depending upon the material ; 

f and a are usually taken as constants ; they are really empirical varia- 
bles, dependent upon the dimensions and character of the column as well as 
upon the material. (Burr.) 

For solid wrought-iron columns, values commonly taken are : / = 36,000 

to40,000;a^3^-to^. 

New York City Building Laws 1897-1898 give the following values for/ : 

Cast iron /= 80,000 lbs. 

Rolled steel .... /= 48,000 lbs. 

Wrought or rolled iron / = 40,000 lbs. 

American oak . . . / — 6,000 lbs. 

Pitch or Georgia pine . / = 5,000 lbs. 

White pine and spruce /= 3,500 lbs. 

For solid cast-iron columns, /= 80,000, a = ~^r^r. 

80 000 
For hollow cast-iron columns, fixed ends, p = j , I = length and 

1 + 800- 

d = diameter in the same unit, and^> = strength in lbs. per square inch. 

Sir Benjamin Baker gives, 

For mild steel / = 67,000 lbs., a — . 

For strong steel /= 114,000 lbs.,a = 



14,400 



STBEICTH ©JF MATERIALi. 

The terms stress and strain are generally used synonymously, authorities 
differing as to which is the proper use. Merriman defines sti-ess as a force 
which acts in the interior of a body, and resists the external forces which 
tend to change its shape. A deformation is the amount of change of shape 
of a body caused by the stress. The word strain is often vised as synony- 
mous with stress, and sometimes it is also used to designate the deforma- 
tion. Merriman gives the following general laws for simple tension or 
compression, as having been established by experiment. 

a. When a small stress is applied to a body, a small deformation is pro- 
duced, and on the removal of the stress the body springs back to its original 
form. For small stresses, then, materials may be regarded as perfectly 
elastic. 

b. Under small stresses the deformations are approximately proportional 
to the forces or stresses which produce them, and also approximately pro- 
portional to the length of the bar or body. 

c. When the stress is great enough, a deformation is produced which is 
partly permanent; that is, the body does not spring back entirely to its 
original form on removal of the stress. This permanent part is termed a 
set. In such cases the deformations are not proportional to the stress. 

d. When the stress is greater still, the deformation rapidly increases, and 
the body finally ruptures. 

e. A sudden shock or stress is more injurious than a steady stress, or than 
a stress gradually applied. 



804 FOUNDATIONS AND STRUCTURAL MATERIALS. 



The elastic limit of a material under test for tensile strength is defined as 
the point where the rate of stretch begins to increase, or where the defor- 
jmations cease to be proportional to the stresses, and the body loses its 
power to return completely to its former dimensions when the stress is re- 
moved. 

modulus of Elasticity. 

The modulus or coefficient of elasticity is the term expressing the relation 
of the amount of extension or compression of a material under stress to the 
load producing that stress or deformation. It is the load per unit of section 
divided by the extension per unit of length. 
If P ■=. applied load, 

le == sectional area of piece, 
I ■=. length of the part extended, 
A. = amount of extension, 
M — modulus of elasticity, 

M — P ' A — Pl 

k • l~ kk 

Following are the Moduli of elasticity for various materials. 

Brass, cast 9,170,000 

" wire 14,230,000 

Copper 15,000,000 to 18,000,000. 

Lead 1,000,000 

Tin, cast 4,600,000 

Iron, cast 12,000,000 to 27,000,000 (?) 

Iron, wrought 22,000,000 to 29,000,000 

Steel 26,000,000 to 32,000,000 

Marble 25,000,000 

Slate 14,500,000 

Glass 8,000,000 

Ash 1,600,000 

Beech 1,300,000 

Birch 1,250,000 to 1,500,000 

Fir 869,000 to 2,191,000 

Oak 974,000 to 2,283,000 

Teak 2,414,000 

Walnut 306,000 

Pine, long-leaf (butt-logs) . . 1,119,200 to 3,117,000 Average, 1,926,00 

factor of Safety. 

This may be defined as the factor by which the breaking strength of a 
material is divided to obtain a safe working-stress. The factor of safety is 
sometimes a rather indefinite quantity, owing to lack of information as to 
the strength of materials, and it is now becoming common to name a defi- 
nite stress which is substantially the result of dividing the average strengths 
by a factor. 

The following factors are found in the " Laws Relating to Building in 
New York City," 1897-1898. 

For beams, girders, and pieces subject to transverse strains, factor of 
safety = 4. 

For wrought-iron or rolled-steel posts, columns, or other vertical sup- 
ports, 4. 

For other materials subject to a compressive strain, 5. 

For tie-rods, tie-beams, and other pieces subject to tensile strain, 6. 

IftEOMEK'T OF INERTIA. 

The moment of inertia of a body about any axis, is the sum of the products 
of the mass of each particle of the body, into the square of its (least) dis- 
tance from the axis. 



MOMENT OF INERTIA. 805 



RAMUS Of «l«ATIO\. 

The radius of gyration of a section is the square root of the quotient of 
the moment of inertia, divided, hy the area of the section, or 



Radius of gyrations /Moment of inertia 
V Area of section. 

The radius of gyration of a solid about an axis is equal to the 



V 



Moment of Inertia 
Mass of the Solid 



Use in the Formulae for Strength of dirders and 

Columns. 

The strength of sections to resist strains, either as girders or as 
columns, depends on the form of the section and its area, and the property 
of the section which forms the basis of the constants used in the formulae 
for strength of girders and columns to express the effect of the form, is its 
moment of inertia about its neutral axis. Thus the moment of resistance 
of any section to transverse bending is its moment of inertia divided by the 
distance from the neutral axis to the fibers farthest removed from the axis ; 
or 

,.. -. • x Moment of inertia „, I 

Moment of resistance = -p-r— ^ — - -^ ^ r-. M = — . 

Distance of extreme fiber from axis e 

Moment of Inertia of Compound Shapes. . 

(Pencoyd Iron Works.) 

The moment of inertia of any section about any axis is equal to the I about 
a parallel axis passing through its center of gravity -J- (the area of the sec- 
tion x the square of the distance between the axes). 

By this rule, the moments of inertia or radii of gyration of any single sec- 
tions being knoAvn, corresponding values may be obtained for any combina- 
tion of these sections. 

Radius of titration of Compound Shapes. 

In the case of a pair of any shape without a web the value of R can always 
be found without considering the moment of inertia. 

The radius of gyration for any section round an axis parallel to another 
axis passing through its center of gravity is found as follows : 

Let r = radius of gyration around axis through center of gravity ; R = 
radius of gyration around another axis parallel to above ; d =z distance be- 
tween axes : 

R = Vd* -J- r 2 

When r is small, R may be taken as equal to cl without material error. 

EIEMEITi OF UilJAI SECTION'S. 

Moments refer to horizontal axis through center of gravity. This table is 
intended for convenient application where extreme accuracy is not impor- 
tant. Some of the terms are only approximate ; those marked * are cor- 
rect. Values for radius of gyration in flanged beams apply to standard 
minimum sections only. 

A = area of section ; 

b =. breadth ; 

h — depth ; 
D = diameter. 



806 



FOUNDATIONS AND STRUCTURAL MATERIALS. 



Shape of Section. 


Moment of 
Inertia. 


Moment 

of 

Resistance. 


Square of 

Least 
Radius of 
Gyration. 


Least 
Radius of 
Gyration. 




— i 


Solid Rect- 
angle. 


bW* 
12 


bW* 
6 


/Least \ 2 * 
I Side J 


Least side* 








12 






-6— 






r— *i * 


Hollow Rect- 
angle. 


bW—b x h^ * 


bW — bJif* 


W -f h* * 


h + W 




12 


6h 


12 


4.89 


<. 


-&--> 







Solid Circle. 


AD** 
16 


AD* 

8 


Z> 2 * 


D* 
4 


-ip- 


Hollow Circle 
A, area of 

large section ; 
a, area of 

small section. 


AW— ad* 


AD*— ad 2 


Z) 2 +rf 2 * 

16 


D + d 


16 


8D 


5.64 


-7 


A — T 


Solid 
Triangle. 


bW 
36 


bW 

24 


The least 

of the two: 

h 2 W 

18 ° r 24 


The leist 

of the two : 

h b 


-6— H 


4.24 4.9 




i 


Even Angle. 


AW 
10.2 


Ah 

7.2 


63 

25 


b 
5 




>* 




-6—^1 






O 


Uneven Angle 


AW 
9.5 


Ah 
6.5 


(fc&) 2 


hb 




fe l 


13(A 2 +6 2 ) 


2.6 (ft + 6) 


HB 


Even Cross. 


AW 
19 


Ah 
9.5 


ft 2 
22.5 


4.74 




A^ 


Even Tee. 


AW 

ILT 


8 


6 2 
22^5 


5 
4.74 


L-A-J 






<---f/i->- 


I-Beam. 


AW 
6.66 


3.2 


W 
21 


b 
4.58 




Channel. 


7.34 


^7i 
3.67 


6 2 
12.5 






Hi 


6 
3^54 


"1 

rC 

-J 


te 


Deck Beam. 


^A 2 
6.9 


Ah 
4 


6 2 
36.5 


b 
6 



Distance of base from center of gravity, solid triangle, — ; even angle, 
— ; uneven angle, -r-^-; even tee, 7^; deck beam, ^^ ; all other shapes 



3.5 ' 
^ h D 
given in the table, -z or — 



3.3 



ELEMENTS OF USUAL SECTIONS. 807 

Solid Cast-iron Columns. 

Table, based on Hodgkinson's formula (gross tons). 

The figures are one-tenth of the breaking weight in tons, for solid col- 
umns, ends flat and fixed. 



.5 

a » 

S3 






Length of Column 


n Feet. 








6. 


1 

8. 


10. 


12. 


14. 


16. 


18. 


20. 


25. 


H 


.82 


.50 


.34 


.25 


.19 


.15 


.13 


.11 


.07 


i-l 


1.43 


.87 


.60 


.44 


.34 


.27 


.22 


.18 


.13 


2 


2.31 


1.41 


.97 


.71 


.55 


.44 


.36 


.30 


.20 


2i 


3.52 


2.16 


1.48 


1.08 


.83 


.67 


.54 


.46 


.31 


2* 


5.15 


3.16 


2.16 


1.58 


1.22 


.97 


.80 


.66 


.56 


2| 


7.26 


4.45 


3.05 


2.23 


1.72 


1.37 


1.12 


.94 


.64 


3 


9.93 


6.09 


4.17 


3.06 


2.35 


1.87 


1.53 


1.28 


.88 


3£ 


17.29 


10.60 


7.26 


5.32 


4.10 


3.26 


2.67 


2.23 


1.53 


4 


27.96 


17.15 


11.73 


8.61 


6.62 


5.28 


4.32 


3.61 


2.47 


4£ 


42.73 


26.20 


17.93 


13.15 


10.12 


8.07 


6.60 


5.52 


3.78 


5 


62.44 


38.29 


26.20 


19.22 


14.79 


11.79 


9.65 


8.06 


5.52 


5* 


88.00 


53.97 


36.93 


27.09 


20.84 


16.61 


13.60 


11.37 


7.78 


6 


120.4 


73.82 


50.51 


37.05 


28.51 


22.72 


18.60 


15.55 


10.64 


64 


160.6 


98.47 


67.38 


49.43 


38.03 


30.31 


24.81 


20.74 


14.19 


7 


209.7 


128.6 


87.98 


64.53 


49.66 


39.57 


32.30 


27.08 


18.53 


7i 


268.8 


164.8 


112.8 


82.73 


63.66 


50.73 


41.53 


34.72 


23.76 


8 


339.1 


207.9 


142.3 


104.4 


80.31 


64.00 


52.39 


43.80 


29.97 


8i 


421.8 


258.6 


177.0 


129.8 


99.90 


79.61 


65.16 


54.48 


37.28 


9 


518.2 


317.7 


217.4 


159.5 


122.7 


97.80 


80.05 


66.92 


45.80 


9i 


629.5 


386.0 


264.2 


193.8 


149.1 


118.8 


97.25 


81.70 


55.64 


10 


757.2 


464.3 


317.7 


233.1 


179.3 


142.9 


117.0 


97.79 


66.92 


10J 


902.6 


553.5 


378.7 


277.8 


213.8 


170.3 


139.4 


116.6 


79.77 


11 


1067.1 


654.4 


447.8 


328.5 


252.7 


201.4 


164.9 


137.8 


94.31 


Hi 


1252.3 


767.9 


525.5 


385.4 


296.6 


236.4 


193.5 


161.7 


110.7 


12 


1459.6 


895.1 


612.5 


449.3 


345.7 


275.5 


225.5 


188.5 


129.0 



Where the length is less than 30 diameters, 
Strength in tons of short columns 



SC 



lOS-j-fC" 

S being the strength given in the above table, and C=49 times the sec- 
tional area of the metal in inches. 

Hollow Columns. 

The strength nearly equals the difference between that of two solid col- 
umns, the diameters of which are equal to the external and internal diam- 
eters of the hollow one. 

More recent experiments carried out by the Building Department of New 
York City on full-size cast-iron columns, and other tests made at the 
Watertown Arsenal on cast-iron mill columns, show Gordon's formula, 
based on Hodgkinson's experiments, to give altogether too high results. 

The following table, from results of the New York Building Department 
tests, as published in the Engineering News, January 13-20, 1898, show actual 
results on columns such as are constantly used in buildings. Applying 
Gordon's formula to the same columns gives the following as the breaking 
load per square inch. For 15-inch columns, 57,000 lbs.; for 8-inch and 6-inch 
columns, 40,000 lbs., all of which are much too high, as shown by the table. 

Prof. Lanza gives the average of 11 columns in the Watertown tests as 
29,600 pounds per square inch, and recommends that 5,000 pounds per square 
inch be used as the maximum safe load for crushing strength. 



808 FOUNDATIONS AND STRUCTURAL MATERIALS. 







rests of 


Cast-iron Columns. 










Thickness. 


Breaking Load. 




Diam. 

Inches. 






















Max. 


Min. 


Average. 


Pounds. 


Pounds 
per sq. in. 


j 


15 


1 


1 


1 


1,356,000 


30,830 


2 


15 


WW 


1 


1* 


1,330,000 


27,700 


3 


15 


11 


1 


H 


1,198,000 


24,900 


4 


15J 


1& 


1 


1* 


1,246,000 


25,200 


5 


15 


41 


1 


1H 


1,632,000 


32,100 


6 


15 


li 


1* 


1« 


2,082,000+ 


40,400+ 


i 


7f to 8£ 


li 


1 


1 


651,00 


31,900 


8 


8 


1A 


1 


1ft 


612,800 


26,800 


9 


6A 


1 5 
if 

8 


1* 


1ft 


400,000 


22,700 


10 


6 5 3 5 


1A 


1ft 


455,200 


26,300 



Ultimate Strength of Hollow, Cylindrical Wrought and 
Cast-iron Columns, when fixed at the End*. 

(Pottsville Iron and Steel Co.) 

Computed hy Gordon's formula, _p = — 



p = Ultimate strength in lbs. per square inch ; 

I = Length of column, ) ,., . ooWl „ , .'. 

h = Diameter of column, } both m same units 5 

I 40,000 lbs. for wrought iron; ) 

\ 80,000 lbs. for cast iron; { 

C ■=. 1/3000 for wrought iron, and 1/800 for cast iron. 
),000 



/= 



For cast iron, p ■=.- 



For wrought 



1 + 
ron, p = — 



40,000 



1 + 



WAY 

300 V hj 



3,(100 





Hollow 


Cylindrical 


Columns. 




Ratio of 


Maximum Load per sq. in. 


Safe Load per Square Inch. 


Length to 










Diameter. 










1 
h 


Cast Iron. 


Wrought Iron. 


Cast Iron, 
Factor of 6. 


Wrought Iron, 
Factor of 4. 


8 


74075 


39164 


12346 


9791 


10 


71110 


38710 


11851 


9677 


12 


67796 


38168 


11299 


9542 


14 


64256 


37546 


10709 


9386 


16 


60606 


36854 


10101 


9213 


18 


56938 


36100 


9489 


9025 


20 


53332 


35294 


8889 


8823 


22 


49845 


34442 


8307 


8610 


24 


46510 


33556 


7751 


8389 


26 


43360 


32642 


7226 


8161 


28 


40404 


31712 


6734 


7928 


30 


37646 


30768 


6274 


7692 



ELEMENTS OF USUAL SECTIONS. 



809 



Hollow Cylindrical Columns. — Continued. 



Ratio of 


Maximum Load per Sq. In. 


Safe Load pei 


Square Inch. 


Length, to 










Diameter. 










1 

h 


Cast Iron. 


Wrought Iron. 


Cast Iron, 
Factor of 6. 


Wrought Iron, 
Factor of 4. 


32 


35088 


29820 


5848 


7455 


34 


32718 


28874 


5453 


7218 


36 


30584 


27932 


5097 


6983 


38 


28520 


27002 


4753 


6750 


40 


26666 


26086 


4444 


6522 


42 


24962 


25188 


4160 


6297 


44 


23396 


24310 


3899 


6077 


46 


21946 


23454 


3658 


5863 


48 


20618 


22620 


3436 


5655 


50 


19392 


21818 


3262 


5454 


52 


18282 


21036 


3047 


5259 


54 


17222 


20284 


2870 


5071 


56 


16260 


19556 


2710 


4889 


58 


15368 


18856 


2561 


4714 


60 


14544 


18180 


2424 


4545 



Ultimate Streng-tn of Wi-oug-ht-iron Columns. 

p — ultimate strength per square inch; 
Z= length of column in inches; 
r — least radius of gyration in inches. 

™ A T. 40000 

For square end-bearmgs, p =r 



1 + 



For one pin and one square bearing, p : 



40000 
40000 



(0 



1+ 



000 \rj 



For two pin hearings, 



V 



30000 
40000 



1 + 



20000 \rl 

For safe working-load on these columns use a factor of 4 when used in 
buildings, or when subjected to dead load only; but when used in bridges 
the factor should be 5. 

Wroiig-Ist-lron Columns. 





Ultimate Strength in Lbs. 




Safe Strength in 


Lbs. per 


1 


per Square Inch. 


I 
r 


Square Inch — Factor of 5. 


r 


Square 


Pin and 


Pin 


Square 


Pin and 


Pin 




Ends. 
39944 


Sq. End. 
39866 


Ends. 




Ends. 


Sq. End. 


Ends. 


10 


39S00 


10 


7989 


7973 


7960 


15 


39776 


39702 


39554 


15 


7955 


7940 


7911 


20 


39604 


39472 


39214 


20 


7921 


7894 


7843 


25 


39384 


39182 


38788 


25 


7877 


7836 


7758 


30 


39118 


38834 


38278 


30 


7821 


7767 


7656 


35 


38810 


38430 


37690 


35 


7762 


7686 


7538 


40 


38460 


37974 


37036 


40 


7692 


7595 


7407 


45 


3S072 


37470 


36322 


45 


7614 


7494 


7264 


50 


37646 


36928 


35525 


50 


7529 


7386 


7105 


55 


37186 


36336 


34744 


55 


7437 


7267 


6949 


60 


36697 


35714 


33898 


60 


7339 


7143 


6780 


65 


36182 


34478 


33024 


65 


7236 


6896 


6605 


70 


35634 


34384 


32128 


70 


7127 


6877 


6426 


75 


35076 


33682 


31218 


75 


7015 


6736 


6244 


80 


34482 


32«66 


30288 


80 


6896 


6593 


6058 


85 


33883 


32236 


29384 


85 


6777 


6447 


5877 


90 


33264 


31196 


28470 


90 


6653 


6299 


5694 


95 


32636 


30750 


27562 


95 


6527 


6150 


5512 


100 


32000 


30U00 


2b666 


100 


6400 


6000 


5333 


105 


31357 


29250 


25786 


105 


6271 


5850 


5157 



810 FOUNDATIONS AND STRUCTURAL MATERIALS. 



TRANSVERSA STRENGTH. 

Transverse strength of bars of rectangular section is found to vary di- 
rectly as the breadth of the specimen tested, as the square of its depth, and 
inversely as its length. The deflection under load varies as the cube of the 
length, and inversely as the breadth and as the cube of the depth. Alge- 
braically, if S = the strength and D the deflection, I the length, b the 
breadth, and d the depth, 

bd 2 I 3 

S varies as —r- and D varies as j-^t. 
I ba A 

To reduce the strength of pieces of various sizes to a common standard, 
the term modulus of rupture (E) is used. Its value is obtained by experi- 
ment on a bar of rectangular section supported at the ends and loaded in 
the middle, and substituting numerical values in the following formula : 

2 bd^ 
in which P = the breaking load in pounds, I = the length in inches, b the 
breadth, and d the depth. 

Fundamental formula; for flexure of Reams. 

(Merriman.) 

Resisting shear =z vertical shear ; 

Resisting moment = bending moment ; 

Sum of tensile stresses = sum of compressive stresses ; 

Resisting shear = algebraic sum of all the vertical components of the in- 
ternal stresses at any section of the beam. 

If A be the area of the section and Ss the shearing unit stress, then resist- 
ing shear = AS* ; and if the vertical shear = V, then V= ASs. 

The vertical shear is the algebraic sum of all the external vertical forces 
on one side of the section considered. It is equal to the reaction of one sup- 
port, considered as a force acting upward, minus the sum of all the vertical 
downward forces acting between the support and the section. 

The resisting moment = algebraic sum of all the moments of the inter- 
nal horizontal stresses at any section with reference to a point in that sec- 
ts'/ 
tion, = — , in which S= the horizontal unit stress, tensile or compressive 

as the case may be, upon the fiber most remote from the neutral axis, c — 
the shortest distance from that fiber to said axis, and /= the moment of 
inertia of the cross-section with reference to that axis. 

The bending moment Mis the algebraic sum of the moment of the external 
forces on one side of the section with reference to a point in that section z= 
moment of the reaction of one support minus sum of moments of loads be- 
tween the support and the section considered. 

M— — . 

c 

The bending moment is a compound quantity = product of a force by the 
distance of its point of application from the section considered, the distance 
being measured on a line drawn from the section perpendicular to the direc- 
tion of the action of the force. 

Concerning the above formula, Prof. Merriman, Eng. News, July 21, 1894, 
says : The formula just quoted is true when the unit-stress S on the part of 
the beam farthest from the neutral axis is within the elastic limit of the 
material. It is not true when this limit is exceeded, because then the neutral 
axis does not pass through the center of gravity of the cross-section, and 
because also the different longitudinal stresses are not proportional to their 
distances from that axis, these two requirements being involved in the de- 
duction of the formula. But in all cases of design the permissible unit- 
stresses should not exceed the elastic limit, and hence the formula applies 
rationally, without regarding the ultimate strength of the material or any 
of the circumstances regarding rupture. Indeed, so great reliance is placed 
upon this formula that tbe practice of testing beams by rupture has been 
almost entirely abandoned, and the allowable unit-stresses are mainly de- 
rived from tensile and compressive tests. 



TRANSVERSE STRENGTH. 



811 













. N 














_ 


&| ■ * ,B * 






_o 


0) <I 

p 






i>|^ ao 03 


03 










W 










s-l 








>, 


i ° ' A 








fl 

c3 


tH fl fl 5 


ShSh&hShSl^l^ 


^.IVSI* 


^1- 


o 

a 

S3 


S 










ii ii ii ii ii ii 


i ii ii 


II 


03 

PQ 


go 
fl-£ t£ 


^ 


$ 






i- 1 fl in 










R 03 03 
'Pg£ 
cS OCG 


*i fc s^ fe jToo ^ ' S fe 7 


k 




HINHInlirtlOO _|_ 1-MCOrH 


KOrH |3 ICO 
CN) 


i-l ICO 




SjS 


A. 








i-* i-* 


co ioo 








Si Us 






a" 

a> 

W 


§o 

03 "d 


CO l<N 


-**>l§3 + -IS 


— Ico — 




=51 


03 O 


R, 






u 
c3 


QhI 










*H I-* 






fl 


■d 


TS 1 % ] % 1 % ' 1 % 1 % 1 


% 1 


1L 


fl 


eS 


,© | h - i >pO k* l-o-o ^rd i~-S h ar S 






oS 


O 


ft^| ftl| ft^| ft;| fc;| fc;| * 


-§r 


§r 


O 


t-I ICOrH ICO CN ICO ■* ICO •# I CO Tf ico^s 


cs 1 


rh ICO 


03 


6B 


II II II II II II 1 

ftn ^ ft, fe. ^ ft, ft. 


\\ 


II 




•9 


ts 


K 




03 

03 


+ 








PQ 


% 










. r} 


•o • 












c3 




03 














r2 




-a • 


















c6 














a • 

3 
3 




o • 

03 

o • 












>> 

73 <D 


rfl (J) 




03 . 










I » 3 






■g 








i 


•^ =8 3 

o "3 g 

03 3 fl 

5 -d - S 


* S 

68 fl « 

'd •-' -£ 

Q T« fl 




■d . 

03 








03 


*~ 03 -O S 03 « 










PQ 


2 1 1 - *- s 1 


o 

03 p<a 


03 






at one end, loa< 
with load distri 
rted at ends, lo 
loaded uniform 
loaded at midd 
at both ends, 1< 
Barlow's ExDe 


"2 ^ ® 


^3 






fl l-> 

1 § - 


o 






^ ^3 


fl 






* a g, a a * a 


03- ^^ 


oT 






2 03 _ 


a 






«h c3 c3 ej l- c$ 


cS 






R 


5Q a 


w 


02 R CO 


r Ji 


R 




32 





812 FOUNDATIONS AND STRUCTURAL MATERIALS. 



formulae for Transverse Streng-th of Beams. 

(Referring to table on preceding page.) 

P ■= load at middle ; 
W— total load, distributed uniformly ; 
I = length ; b = breadth ; d =z depth, in inches ; 
E = modulus of elasticity ; 

R = modulus of rupture, or stress per square inch of extreme fiber ; 
I == moment of inertia ; 

c = distance between neutral axis and extreme fiber. 
For breaking-load of circular section, replace bd 2 by 0.59d 3 . 
For good wrought iron the value of E is about 80,000, for steel about 
120,000, the percentage of carbon apparently having no influence. (Thurs- 
ton, " Iron and Steel," p. 491.) 

For cast iron the value of E varies greatly according to quality. Thurston 
found 45,740 and 67,980 in No. 2 and No. 4 cast iron, respectively. 

For beams fixed at both ends and loaded in the middle, Barlow, by experi- 
ment, found the maximum moment of stress = ^Pl instead of \Pl, the re- 
sult given by theory. Prof. Wood (' ' Resistance Materials," p. 155) says of this 
case, " The phenomena are of too complex a character to admit of a thorough 
and exact analysis, and it is probably safer to accept the results of Mr. Bar- 
low in practice than to depend upon theoretical results." 



APPROXIMATE GREATEST SAFE IOAD IN 
IBS. OUS STEEJL BEAMS. 

(Pencoyd Iron Works.) 

Based on fiber strains of 16,800 lbs. for steel. (For iron the loads should be 
one-sixth less, corresponding to a fiber strain of 14,000 lbs. per square inch.) 

L ■=. length in feet between supports ; 
A = sectional area of beam in square inches ; 
D = depth of beam in inches ; 
a = interior area in square inches ; 
d =. interior depth in inches ; 
w = working-load in net tons. 



Shape 


Greatest Safe Load in Lbs. 


Deflection in Inches. 


of 
Section. 


Load in 
Middle. 


Load 
Distributed. 


Load in 
Middle. 


Load 
Distributed. 


Solid 
Rectangle. 


940^4Z> 
L 


1880^Z> 
L 


wL 3 
32AD 2 


wL 3 

52AD 2 


Hollow 


940 {AD— ad) 
L 


1880(AD—ad) 
L 


wL 3 


wL 3 


Rectangle. 


32(AD 2 —ad 2 ) 


52(AJ) 2 —ad 2 ) 


Solid 
Cylinder. 


700AD 
L 


1400.4 Z> 
L 


wL 3 
MAD 2 


ivL 3 
38A&* 


Hollow 


700 (AD — ad) 
L 


UOO(AD-ad) 
L 


wL 3 


wL 3 


Cylinder. 


2A(AD 2 —ad 2 ) 


38(AD 2 —ad 2 ) 



APPROXIMATE GREATEST SAFE LOAD IN LBS. 813 



Shape 


Greatest Safe Load in Lbs. 


Deflection in Inches. 


of 

Section. 


Load in 
Middle. 


Load 
Distributed. 


Load 
in Middle. 


Load 
Distributed. 


Even- 
legged 
Angle or 
Tee. 


930 AD 
L 


186(U/> 
L 


wL 3 
32 AD* 


wL 3 
52AD 2 


Channel or 
Z Bar. 


imAT) 
L 


Z2WAD 
L 


wL 3 
53AD 2 


wL 3 
85AD* 


Deck 
Beam. 


U50AD 
L 


2900 AD 
L 


50AD 2 


xvL 3 
80AB* 


I-Beam. 


nmAB 

L 


3560viZ> 


wL 3 
58AD 2 


wL 3 
d3AD* 


I 


II 


III 


IV 


V 



The rules for rectangular and circular sections are correct, while those for 
the flanged sections are approximate, and limited in their application to the 
standard shapes as given in the Pencoyd tables. 

The calculated safe loads will be approximately one-half of loads that 
would injure the elasticity of the materials. 

The rules for deflection apply to any load below the elastic limit, or less 
than double the greatest safe load by the rules. 

If the beams are long, without lateral support, reduce the loads for the 
ratios of width to span as follows : 



Length of Beam. 



Proportion of Calculated Load 
forming Greatest Safe Load, 




Whole calculated load 


9-10 


i n 


8-10 


i u 


7-10 


I (( 


6-10 


' " 


5-10 


' " 



These rules apply to beams supported at each end. For beams supported 
otherwise, alter the coefficients of the table as described below, referring to 
the respective columns indicated by number. 

Chang-es of Coefficients for Special Forms of Beams. 



Kind of Beam. 



Fixed at one end, loaded 
at the other. 



Coefficient for Safe 
Load. 



One-fourth of the coeffi- 
cient of col. II. 



Coefficient for Deflec- 
tion. 



One-sixteenth of the co- 
efficient of col. IV. 



814 FOUNDATIONS AND STRUCTURAL MATERIALS. 



Chang-es of Coefficients — Continued. 



Kind of Beam. 


Coefficient for Safe 
Load. 


Coefficient of Deflec- 
tion. 


Fixed at one end, load 
evenly distributed. 


One-fourth of the coeffi- 
cient of col. III. 


Five forty-eighths of the 
coefficient of col. V. 


Both ends rigidly fixed, 
or a continuous beam, 
with a load in middle. 


Twice the coefficient of 
col. II. 


Four times the coeffi- 
cient of col. IV. 


Both ends rigidly fixed, 
or a continuous beam, 
with load evenly dis- 
tributed. 


One and a half times 
the coefficient of col. 
III. 


Five times the coeffi- 
cient of col. V. 



Let 



modulus of Elasticity and Silastic Resistance. 

P =z tensile stress in pounds per square inch at the elastic limit : 
elongation per unit of length at the elastic unit ; 



E = modulus of elasticity = P -f- e 



E. 



1 P 2 





Then elasticity resilience per cubic inch = \Pe = - 

2t E 

BEAMS OJP UWUJFORM: STRJEWOTH THROUGHOUT 
THEIR IEHGTH. 

The section is supposed in all cases to be rectangular throughout. The 
beams shown in plan are of uniform depth throughout. Those shown in 
elevation are of uniform breadth throughout. 

B = breadth of beam. D = depth of beam. 

Fixed at one end, loaded at the other ; 
curve parabola, vertex at loaded end ; PI) 2 
proportional to distance from loaded end. 
The beam may be reversed so that the up- 
per edge is parabolic, or both edges may be 
parabolic. 

Fixed at one end, loaded at the other ; tri- 
angle, apex at loaded end ; PE 2 proportional 
to the distance from the loaded end. 

Fixed at one end ; load distributed ; tri- 
angle, apex at unsupported end ; PEP- pro- 
portional to sqviare of distance from unsup- 
ported end. 

Fixed at one end ; load distributed ; curves 
two parabolas, vertices touching each other, 
at unsupported end ; PE 2 proportional to dis- 
tance from unsupported end. 

Supported at both ends ; load at any one 
point ; two parabolas, vertices at the points 
of support, bases at point loaded ; PE 2 pro- 
portional to distance from nearest point of 
support. The upper edge or both edges may 
also be parabolic. 

Supported at both ends ; load at any one 
point ; two triangles, apices at points of sup- 
port, bases at point loaded ; PE 2 propor- 
tional to distance from the nearest point of 
support. 

Supported at both ends ; load distributed ; 
curves two parabolas, vertices at the middle 
of the beam ; bases center line of beam ; PE 2 
proportional to product of distances from 
points of support. 

Supported at both ends ; load distributed ; 
curve semi-ellipse ; PE 2 proportional to the 
product of the distances from the points of 
support. 





TRENTON BEAMS AND CHANNELS. 



815 



TRENTON BEAMS AA» CHAMELS. 

(Trenton Iron Works.) 

To find which beam, supported at both ends, will be required to support 
with safety a given uniformly distributed load : 

Multiply the load in pounds by the span in feet, and take the beam whose 
" Coefficient for Strength " is nearest to and exceeds the number so found. 
The weight of the beam itself should be included in the load. 

The deflection in inches for such distributed load will be found by divid- 
ing the square of the span taken in feet, by seventy (70) times the depth of 
the beam taken in inches for iron beams, and by 52.5 times the depth for 
steel. 

Example. — Which beam will be required to support a uniformly distrib- 
uted load of 12 tons (= 21,000 lbs.) on a span of 15 feet ? 

2*,000 X 15= 360,000, which is less than the coefficient of the 12i-inch 125- 
lb. iron beam. The weight of the beam itself would be 625 lbs., which, 
added to the load and multiplied by the span, would still give a product less 
than the coefficient; thus, 



24,625 X 15=369,375. 



The deflection will be 



15 x 15 
70 X 12J 



0.26 inch. 



The safe distributed load for each beam can be found by dividing the 
coefficient by the span in feet, and subtracting the weight of the beam. 

When the load is concentrated entirely at the center of the span, one-half 
of this amount must be taken. 

The beams must be secured against yielding sideways, or the safe loads will 
be much less. 

TREKTOH ROLLED STEEL BEAMS. 





Weight 
Y"ard in 


per 


Designation of 


Lbs. 


Beam. 








Min. 


Max. 


15 inch 


150 


190 


15 " 


123 


160 


12 " 


120 


150 


12 " 


96 


125 


10 " 


135 


160 


10 " 


99 


125 


10 " 


76 


100 


9 " 


81 


105 


9 " 


63 


85 


8 " 


66 


85 


8 " 


54 


75 


7 " 


60 


80 


7 " 


46.5 


65 


6 " 


50 


65 


6 " 


40 


55 


5 " 


39 


52 


5 " 


30 


42 


4 " . . . . . 


30 


40 


4 " 


22.5 


32 


2 " 


4* 




H " 


5i 





Width of 

Flanges in 

Inches. 



Thickness 
of Stem. 



Coefficient for 

Strength in 

Lbs., Minimum 

Weight. 



5.75 
5.5 
5.5 
5.25 
5.25 
5.0 
4.75 
4.75 
4.5 
4.5 
4.25 
4.25 
4.0 
3.5 
3.0 
3.13 
3.0 
2.75 
2.62 
.75 
1.50 



753,000 

603,000 

500,000 

407,000 

461.000 

344,000 

264,000 

262,000 

200,000 

192,000 

154,000 

151,000 

118,000 

104,000 

83,300 

67,000 

52,900 

41,200 

31,400 

2,660 

2,300 



816 



FOUNDATIONS AND STRUCTURAL MATERIALS. 





TREarToar iron bje. 


UttS 


AN 1» CMANNJEI-S. 


a 

,3 

M 

'53 

w 


« ci 
cop* 

31 


o.a . 

_, cd <a 


CO £> 
00 <- 

r=< CD 


gP jq . 

CD CD 1 ^ 

O-SHcC 


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.1 

w 


cS l, s 


r* P W 

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■S So 


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2& . 

H <D 02 


o _ ^ .2 
O iH C-l CO 


I-Beams. 


Channels. 


20 


272 


6| 


1! 
IS 


1,320,000 


15 


190 


4| 


1 


625,000 


20 


200 


6 


i 


990,000 


15 


120 


4 


i 


401,000 


15^ 


200 


5| 


.6 


748,000 


m 


140 


4 


16 


381,000 


15 T 3 B 


150 


5 


i 


551,000 


12i 


70 


3 


.33 


200,100 


15| 


125 


5 


.42 


460,000 


10i 


60 


93 


1 


134,750 


12ft 


170 


H 


.6 


511,000 


10 


48 


2^ 


i 5 s 


102,000 


12i 


125 


4.8 


.47 


377,000 


9 


70 


3J 


7 
15 


146,000 


12 


120 


5J 


.39 


375,000 


9 


50 


2| 


.33 


104,000 


12 


96 


5i 


.32 


306,000 


8 


45 


21 


.26 


88,950 


10* 


135 


5 


.47 


360,000 


8 


33 


2.2 


.20 


65,800 


104 


105 


4i 


¥ 


286,000 


7 


36 


2£ 


\ 


62,000 


10J 


90 


« 


5 
16 


250,000 


7 


25£ 


2 


.20 


39,500 


9 


125 


4i 


.57 


268,000 


6 


45 


2i 


.40 


58,300 


9 


85 


^ 


3 


199,000 


6 


33 


2i 


.28 


45,700 


9 


70 


4 


.3 


167,000 


6 


22J 


H 


.18 


33,680 


8 


80 


4^ 


1 


168,000 


5 


19 


If 


.20 


22,800 


8 


65 


4 


.3 


135,000 


4 


l&J 


li 


.20 


15,700 


7 


55 
120 


3| 

5J 


.3 


101,000 
172,000 


3 


15 


11 


.20 


10,500 


6 










6 


90 
50 


5 
3^ 


h 
.3 


132,000 
76,800 






Deck Beams 




6 


8 


65 


# 


f 


91,800 


6 


40 


3 




62,600 


7 


55 


4* 


ft 


63,500 


5 


40 


3 


ft 


49,100 












5 
4 
4 


30 
37 
30 


2| 

3 

2| 


i 

i 


38,700 
36,800 
30,100 






Strut Bars. 




5 


22 


1t 7 b 


ft 


11,900 


4 


18 


2 


ft 


18,000 


5 


16 


1ft 


1 


9,100 



TRENTON BEAMS AND CHANNELS. 



817 



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Size and 

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818 FOUNDATIONS AND STRUCTURAL MATERIALS. 



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cj jh c8 



WOOD. 
Tests of American Woods. 



819 



In all cases a large number of tests were inade of each wood. Minimum 
and maximum results only are given. All of the test specimens had a sec- 
tional area of 1.575 x 1-575 inches. The transverse test specimens were 
39.37 inches between supports, and the compressive test specimens were 

3 PI 
12.60 inches long. Modulus of rupture calculated from formula R : 



P=z load in pounds at the middle, 
d = depth : 



2 bcP 
length in inches, b ■=. breadth, 



Name of Wood. 



Cucumber tree 

Yellow poplar, white wood . . 
White wood, Basswood . . . 
Sugar maple, Rock maple . . 

Red maple 

Locust 

Wild cherry 

Sweet gum 

Dogwood 

Sour gum, pepperidge .... 

.Persimmon 

White ash 

Sassafras 

Slippery elm 

White elm 

Sycamore, Buttonwood . . . 
Butternut, white walnut . . . 

Black walnut 

Shellbark hickory 

Pignut 

White oak 

Red oak 

Black oak 

Chestnut 

Beech 

Canoe birch, paper birch . . . 

Cottonwood 

White cedar 

Red cedar 

Cypress 

White pine 

Spruce pine 

Long-leaved pine, Southern pine 

White spruce 

Hemlock 

Red fir, yellow fir 

Tamarack 



Transverse 


Comp 


ression 


Tests, 


Parallel to 


Modulus of 


Grain, 


pounds 


Rupture. 


per sq. in. 


Min. 


Max. 


Min. 


Max. 


7440 


12050 


4560 


7410 


6560 


11756 


4150 


5790 


6720 


11530 


3810 


6480 


9680 


20130 


7460 


9940 


8610 


13450 


6010 


7500 


12200 


21730 


8330 


11940 


8310 


16800 


5830 


9120 


7470 


11130 


5630 


7620 


10190 


14560 


6250 


9400 


9830 


14300 


6240 


7480 


18500 


10290 


6650 


8080 


5950 


15800 


4520 


8830 


5180 


10150 


4050 


5970 


10220 


13952 


6980 


8790 


8250 


15070 


4960 


8040 


6720 


11360 


4960 


7340 


4700 


11740 


5480 


6810 


8400 


16320 


6940 


8850 


14870 


20710 


7650 


10280 


11560 


19430 


7460 


8470 


7010 


18360 


5810 


9070 


9760 


18370 


4960 


8970 


7900 


18420 


4540 


8550 


5950 


12870 


3680 


6650 


13850 


18840 


5770 


7840 


11710 


17610 


5770 


8590 


8390 


13430 


3790 


6510 


6310 


9530 


2660 


5810 


5640 


15100 


4400 


7040 


9530 


10030 


5060 


7140 


5610 


11530 


3750 


5600 


3780 


10980 


2580 


4680 


9220 


21060 


4010 


10600 


9900 


11650 


4150 


5300 


7590 


14680 


4500 


7420 


8220 


17920 


4880 


9800 


10080 


16770 


6810 


10700 



820 FOUNDATIONS AND STRUCTURAL MATERIALS, 



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wood. 821 

Rule. — To find the safe uniformly distributed load in tons for white pine 
or spruce beams, multiply the number given in the above table by the thick- 
ness of the beam in inches. For beams of other wood, multiply also by the 
following numbers : 

White Oak. Hemlock. White Cedar. Yellow Pine. Chestnut. 
1.45 .99 .60 1.50 1.08 

Formulae for White JPine Beams. 

Subject to vibration from live loads. 

w = safe load in pounds, less weight of beam. 

I =z length of beam in inches. 

d = depth of beam in inches. 

b = breadth of beam in inches. 
For a beam fixed at one end and loaded at the other: 

1000 bd 2 

For a beam fixed at one end and uniformly loaded : 

1000 bd? 



31 
For a beam supported at both ends and loaded at the middle 

2000 bd* 



w — 



31 

For a beam supported at both ends and uniformly loaded : 

4000 bd? 



— 31 

Note. — In placing very heavy loads upon short, but deep and strong 
beams, care should be taken that the beams rest for a sufficient distance on 
their supports to prevent all danger from crushing or shearing at the ends. 
Ordinary timbers crush under 6,000 lbs. per square inch. To assure a safety 
of beam against crushing at the end, divide half of the load by 1000 ; the 
quotient will be the least number of square inches of base that should be 
allowed for each end to rest on. 

Table of Safe Load for Moderately Seasoned White Pine 
Struts or JPillars. 

The following table, exhibiting the approximate strength of white pine 
struts or pillars, with flat ends, is outlined and interpolated from the rule 
of Rondolet, that the safe load upon a cube of the material being regarded 
as unity, the safe load upon a post whose height is, 

12 times the side will be I 



72 



700 pounds per square inch is assumed as the safe load upon a cube of 
white pine. 

The strength of each strut is considered with reference to the first-named 
dimension of its cross-section, so that if the second dimension is less than 
the first, the strut must be supported in that direction, to fulfill the condi- 
tions of the computation. 

The strength of pillars, as well as of beams of timber, depends much on 
their degree of seasoning. Hodgkinson found that perfectly seasoned blocks 
2 diameters long, required in many cases twice as great a load to crush 
them as when only moderately dry. This should be borne in mind when 
building with green timber. 



822 FOUNDATIONS AND STRUCTURAL MATERIALS. 



I. Safe Distributed loads upon Southern Pine Beams 
One Inch in W idth< 

(C. J. H. Woodbury.) 
(If the load is concentrated at the center of the span, the beams will sus- 
tain half the amount as given in the table.) 



<D 




Depth of 


Beam in 


Inches. 








Eh 

9 


2 3 


1* 


5 6 




7 1 8 


9 


w 


11 1 


n\ 


1* '[ 14 | 


15 


16 




Load 


m Pounds per Foot of Span. 






5 


38 86 


154 % 


10 346 


4' 


ro 614 


778 


960 














6 


27 60 


107 1( 


57 240 


3' 


11 427 


540 


667 


807 












7 


20 44 


78 V. 


52 176 


2- 


314 


397 


490 


593 


705 


828 








8 


15 34 


60 < 


)4 135 


1 


54 240 


304 


375 


454 


540 


634 


735 






9 


. . 27 


47 r 


a 107 


1' 


:5 190 


240 


296 


359 


427 


501 


581 


667 


759 


10 


. . 22 


38 ( 


30 86 


1 


.8 154 


194 


240 


290 


346 


406 


470 


540 


614 


11 




32 { 


50 71 


; 


)1 127 


161 


198 


240 


286 


335 


389 


446 


508 


12 




27 < 


:2 60 


. 


52 107 


135 


167 


202 


240 


282 


327 


375 


474 


13 






16 51 




ro 90 


115 


142 


172 


205 


240 


278 


320 


364 


14 






51 44 




30 78 


99 


123 


148 


176 


207 


240 


276 


314 


15 






11 38 


. 


>2 68 


86 


107 


129 


154 


180 


209 


240 


273 


16 






. 34 




[6 60 


76 


94 


113 


135 


158 


184 


211 


240 


17 






. 30 




tl 53 


67 


83 


101 


120 


140 


163 


187 


217 


18 










56 47 


60 


74 


90 


107 


125 


145 


167 


190 


19 










. 43 


54 


66 


80 


96 


112 


130 


150 


170 


20 










. 38 


49 


60 


73 


86 


101 


118 


135 


154 


21 












44 


54 


66 


78 


92 


107 


122 


139 


22 














50 


60 


71 


84 


97 


112 


127 


23 














45 


55 


65 


77 


89 


102 


116 


24 
















50 


60 


70 


82 


94 


107 


25 
















46 


55 


65 


75 


86 


98 



II. 



Distributed JLoads upon Southern Pine Beams Suf- 
ficient to Produce Standard Limit of Deflection. 















(C. 


J. H 


Woodbury.) 
















Depth of Beam in Inches. 


o . 


l=H 


2 3 4 


5 


6 


7 


8 


9 


10 


11 I 12 


13 1 14 I 15 1 16 


■j3 co 


ft 

02 


Load in Pounds per Foot of Span. 




5 


3 


10 


23 


44 


77 


122 


1182 


259 
















.0300 


6 


2 


7 


16 


31 


53 


85 


126 


180 


247 














.0432 


7 




5 


12 


23 


39 


62 


93 


132 


181 


241 












.0588 


8 




4 


9 


17 


30 


48 


71 


101 


139 


185 


240 


305 








.0768 


9 






7 


14 


24 


38 


56 


80 


110 


146 


190 


241 


301 






.0972 


10 






6 


11 


19 


30 


46 


65 


89 


118 


154 


195 


244 


300 




.1200 


11 








9 


16 


25 


38 


54 


73 


98 


127 


161 


202 


248 


301 


.1452 


12 










13 


21 


32 


45 


62 


82 


107 


136 


169 


208 


253 


.1728 


13 










11 


18 


27 


38 


53 


70 


91 


116 


144 


178 


215 


.2028 


14 












16 


23 


33 


45 


60 


78 


100 


124 


153 


186 


.2352 


15 












14 


20 


29 


40 


53 


68 


87 


108 


133 


162 


.2700 


16 














18 


25 


35 


46 


60 


76 


95 


117 


147 


.3072 


17 














16 


22 


31 


41 


53 


68 


84 


104 


126 


.3468 


18 
















20 


27 


37 


47 


60 


75 


93 


112 


.3888 


19 
















18 


25 


33 


43 


54 


68 


83 


101 


.4332 


20 


















22 


30 


38 


49 


61 


75 


91 


.4800 


21 


















20 


27 


35 


44 


55 


68 


83 


.5292 


22 




















24 


32 


40 


50 


62 


75 


.5808 


23 




















22 


29 


37 


46 


57 


69 


.6348 


24 






















27 


34 


42 


52 


63 


.6912 


25 


.. 








1 •• 




.. | .. 






25 


31 | 39 


48 


58 1.7500 



MASONRY. 



823 



jwAjsonritY. 



Brick- Work. 



Brick work is generally measured by 1000 bricks laid in the wall. In con- 
sequence of variations in size of bricks, no rule for volume of laid brick can 
be exact. The following scale is, however, a fair average. 



7 common bricks to a super, 
14 
21 
28 
35 



ft. 4-inch wall. 

9-inch " 

13-inch " 

18-inch " 

22-inch " 



Corners are not measured twice, as in stone-work. Openings over 2 feet 
square are deducted. Arches are counted from the spring. Fancy work 
counted 1£ bricks for 1. Pillars are measured on their face only. 

One thousand bricks, closely stacked, occupy about 56 cubic feet. 

One thousand old bricks, cleaned and loosely stacked, occupy about 72 cu- 
bic feet. 

One cubic foot of foundation, with one-fourth inch joints, contains 21 
bricks. In some localities 24 bricks are counted as equal to a cubic foot. 

One superficial foot of gauged arches requires 10 bricks. 

Stock bricks commonly measure 8| inches by 4£ inches by 2| inches, and 
weigh from 5 to 6 lbs. each. 

Paving bricks should measure 9 inches by 4| inches by If inches, and 
weigh about \\ lbs. each. 

One yard of paving requires 36 stock bricks, of above dimensions, laid flat, 
or 52 on edge; and 35 paving bricks, laid flat, or 82 on edge. 

The following table gives the usual dimensions of the bricks of some of 
the principal makers. 



Description. 


Inches. 


Description. 


Inches. 


Baltimore front . 
Philadelphia front 
Wilmington front 
Trenton front 
Croton .... 
Colabaugh . . . 


j> 81 X H X 2| 

8i X 4 X 2i 
8i X 3f X 2f 


Maine .... 
Milwaukee . . 
North River . 
Trenton . . . 

Ordinary . . . 


7i X 3| X 2| 
8£ X 41 X 2| 
8 X 3i X 2\ 
8 X 4 X 2\ 
f 7| X 3f X 2\ 
\ 8 X 4i X 2i 



Fire Brick 



( Valentine's (Woodbridge, N. J.) 



g X 4f x 2i inches 



I Downing' s (Allentown, Pa.) . . . . 9 x 4£ X 2\ inches 



To compute the number of bricks in a square foot of wall. — To the face 
dimensions of the bricks used, add the thickness'of one joint of mortar, and 
multiply these together to obtain the area. Divide 144 square inches by 
this area, and multiply by the number of times which the dimension of the 
brick, at right angles to its face, is contained in the thickness of the wall. 



Example. — How many Trenton bricks in a square foot of 12-inch wall, 
the joints being \ inch thick ? 

S+T X W+i — 20 - 62 ; 144 -r 20 - 62 = 7 5 7X3 = 21 bricks per square ft. 



824 FOUNDATIONS AND STRUCTURAL MATERIALS. 



"Weig-ht and Sulk of Bricks. 









Number of Bricks, 


Gross 
Tons. 






by itself. 


in wall with cement. 


Pounds. 


Cu. ft. 


C. Brick. 


F. Brick. 


0. Brick. 


F. Brick. 


1 


2240 


22.4 


448 


416.6 


381 


347 


0.04464 


100 


1 


20 


18.6 


17 


15J 


2.23 


5000 


50.00 


1000 930 


850 


772 


2.4 


5376 


53.76 


1075 


1000 


914 


834 


2.62 


5872 


58.72 


1130 


1100 


1000 


913 


2.88 


6451 


64.51 


1240 


1200 


1100 


1000 



One perch of stone is 24.75 cubic feet. 
In New York City laws a cubic foot of brick-work is deemed to weigh 
115 lbs. 
Building-stone is deemed to weigh 160 lbs. per cubic foot. 
The safe load for brick-work according to the New York City Laws is as 
folio \vs : — 
In tons per superficial foot, 

For good lime mortar 8 tons. 

For good lime and cement mortar mixed . 11£ tons. 
For good cement mortar 15 tons. 

Average Ultimate Crushing--IiOad in Pounds per Square 
Inch for Bricks, Stones, Mortars, and Cements. 



Lbs. per 
Sq. In. 



Brick, common (Eastern) 

Brick, best pressed 

Brick (Trautwine) 

Brick, paving, average of 10 varieties (Western) 

Brick- work, ordinary 

Brick-work, in good cement 

Brick-work, first-class, in cement 

Concrete (1 part lime, 3 parts gravel, 3 weeks old) 

Lime mortar, common 

Portland cement, best English, 

Pure, three months old 

Pure, nine months old 

1 part sand, 1 part cement, 

Three months old 

Nine months old 

Granites, 7750 to 22,750 

Blue granite, Fox Island, Me 

Blue granite, Staten Island, N. Y 

Gray granite, Stony Creek, Conn 

North River (N. Y.) flagging 

Limestones, 11,000 to 25,000 

Limestone from Glen's Falls, N. Y. ... 

Lake limestone, Lake Champlain, N. Y. . . 

White limestone, Marblehead, O 

White limestone from Joliet, 111 

Marbles, 

From East Chester, N. Y 

Common Italian 

Vermont (Souther! and Falls Co.) .... 

Vermont, Dorset, Vt 

Drab, North Bay Quarry, Wis 



10000 

12000 

770 to 4660 

7150 
300 to 500 
450 to 1000 
930 
620 
770 

3760 



2480 
4520 
12000 
14875 
22250 
15750 
13425 
12000 
11475 
25000 
11225 
12775 

12950 
11250 
10750 
7612 
20025 



MISCELLANEOUS MATERIALS. 



825 



Averag-e Ultimate Crushing-- JLoad — Continued. 



Lbs. per 
Sq. In. 



Sandstones 

Brown, Little Falls, N. Y 

Brown, Middletown, Conn 

Bed, Haverstraw, N. Y 

Bed-brown, Seneca freestone, Obio . . . 

Freestone, Dorcbester, N. B 

Longmeadow sandstone, Springfield, Mass. 



6000 
9850 
6950 
4350 
9687 
9150 
8000 to 14000 



MliCEIIAIVEOUi MATERIALi. 
"Weight of Round Bolt Copper Per foot. 



Incbes. 


Pounds. 


Incbes. 


Pounds. 


Incbes. 


Pounds. 


I 


.425 


1 


3.02 


if 


7.99 


h 


.756 


1* 


3.83 


9.27 


f 


1.18 


li 

If 


4.72 


H 


10.64 


1 


1.70 


5.72 


2 


12.10 


$ 


2.31 


li 


6.81 







Weight of Sheet and Bar Bra; 



Thick- 
ness. 
Incbes. 



Sbeets 

per 
sq.ft. 



2.7 
5.41 
8.12 
10.76 
13.48 
16.25 
19. 
21.65 
24.3 
27.12 
29.77 
32.46 
35.18 
37.85 
40.55 
43.29 



Square 

Bars 

1 ft. long 



.015 
.055 
.125 

.225 

!sio 

.51 
.69 
.905 
1.15 
1.4 
1.72 
2.05 
2.4 
2.75 
3.15 
3.65 



Round 


Tbick- 


Sbeets 


Bars 


ness. 


per 


1 ft. long. 


Incbes. 


sq. ft. 


lbs. 




lbs. 


.011 


it 


45.95 


.045 


48.69 


.1 


l T 3 g 


51.4 


.175 


H 


54.18 


.275 


1& 


56.85 


.395 


11 


59.55 


.54 


It 


62.25 


.71 


65. 


.9 


1 T 9 6 


67.75 


1.1 


If 


70.35 


1.35 


1 11 

1? 


73. 


1.66 


75.86 


1.85 


114 


78.55 


2.15 


it 


81.25 


2.48 


m 


84. 


2.85 


2 


86.75 



Square 
Bars 

1 ft. long, 



lbs. 

4.08 

4.55 

5.08 

5.65 

6.22 

6.81 

7.45 

8.13 

8.83 

9.55 

10.27 

11. 

11.82 

12.68 

13.5 

14.35 



Round 

Bars 

1 ft. long. 



lbs. 
3.20 
3.57 
3.97 
4.41 
4.86 
5.35 
5.85 
6.37 
6.92 
7.48 
8.05 
8.65 
9.29 
9.95 
10.58 
11.25 



Composition of Various Grades of Rolled Brass. 



Trade Name. 



Common higb brass . . 

Yellow metal 

Cartridge brass .... 

Low brass 

Clock brass 

Drill rod 

Spring brass 

18 per cent German silver 



Copper. 


Zinc. 


Tin. 


61.5 


38.5 




60 


40 




66f 


33J 




80 


20 




60 


40 




60 


40 




66§ 


33^ 


1* 


6U 


201 





Lead. Nickel. 



1* 
li to 2 



18 



826 



FOUNDATIONS AND STRUCTURAL MATERIALS. 



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s 5 



MISCELLANEOUS MATERIAL. 



827 



Galvanized Iron Wire Rope. 

For Ships' Rigging and Guys for Derricks. 

CHARCOAL ROPE. 











a> 






to 


II 

o _ 

- - 

o"" 




Cir. of New 
Manila Rop 
of Equal 
Strength. 


Breaking 
Strain in 
Tons o f 
2000 Lbs. 


o 

CD • 

2 ° 


®-3 

tjf 

III 


Cir. of New 
Manila Rop< 
of Equal 
Strength. 


O £ 

2 ^°' 
PQoqo 


5£ 


26i 


11 


43 


91 


5£ 


5 


9 


5i 


24£ 


10J 


40 


2| 


^ 


*t 


8 


5 


22 


10. 


35 


2 


3^ 


4* 


7 


s 


21 


9| 


33 


If 


2^ 


3f 


5 


19 


9 


30 




•2 


3 


3* 


4i 


16£ 


8* 


26 


11 


If 


2* 




4 


14i 


8 


23 


li 


2* 


2J 


3| 


12| 


6? 


20 




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2 


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16 


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9i 


6 


14 


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f 


3 


8 


5f 


12 


j 




li 


! 


2| 


6| 


5i 


10 


i 


1* 



Transmission and Standing- Rope. 

With 6 Strands of 7 Wires Each. 

IROX. 



<x> 




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11 


1* 


4f 


3.37 


36 


9 


10 


13 


12 


1* 


4i 


2.77 


30 


7A- 


9 


12 


13 


H 


1 


2.28 


25 


6i 


8* 


10f 


14 


lir 


1.82 


20 


5 


S 


9* 


15 


l 


3 


1.50 


16 


4 


8i 


16 


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2f 


1.12 


12.3 


3 


5| 


7* 


17 


f 


2| 


0.88 


8.8 


2i 


4f 


61 


18 




2|r 


0.70 


7.6 


2 


4A- 


6 


19 




1* 


0.57 


5.8 


1* 


4 


5i 


20 


9 
1 


it 


0.41 


4.1 


1 


3i 


4* 


21 


0.31 


2.83 


t 


2| 


4 


22 




ii 


* 0.23 


2.13 


2h 


3i 


23 


* 


H 


0.19 


1.65 




2i 


2| 


1 24 




i 


0.16 


1.38 




2 


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25 


32 


X 


0.125 


1.03 




If 


2i 








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11 


li- 


3 


3.37 


62 


13 


13 


*' 


12 


1# 


2.77 


52 


10 


12 


8 


13 


It 


1 


2.28 


44 


9 


11 


3 


14 


1.82 


36 


% 


10 


15 


1 


3 


1.50 


30 


6 


9 


5| 


16 


i 


2| 


1.12 


22 


4J 


8 


5 



















828 FOUNDATIONS AND STRUCTURAL MATERIALS. 



Transmission 



and Standing 

CAST STEEL. 



Rope. — Continued. 









+=> i 


H 








u 




OP 

5 


O <D £ 

o a© 


■38 


A B o 




t> 


fii 




6 °° 


£8 

CO 


O <M 


od 


3 


S3 


CD 




MO 


. o o 




0,^ 

■S3*; 


H 


.5 


3 

o 

5 


Weigh 
in Lbs 
with H 
ter. 


^ O 


Propex 
ing L 
Tons 
Lbs. 


Circun 
of new 
Rope o 
Streng 


. B «> 

S 2^ 

Sa.3 


17 


t 


2| 


0.88 


17 


3* 


7 


4* 


18 


-J 


24 


0.70 


14 


3 


6 


4 


19 


11 


0.57 


11 


2i 


5* 


34 


20 


_9_ 


If 


0.41 


8 


If i 


4f 


3 


21 




If 


0.31 


6 


14 


4 


2* 


22 




U 


0.23 


44 


11 


34 


21 


23 


1 


i* 


0.19 


4 


1 


31 


2 


24 


fk 


l 


0-16 


3 


1 


2} 


If , 


25 


A 


1 


0.12 


2 


£ 


21 


14 



X*lia1»le Hoisting 1 Mope. 

With 6 strands of 19 Wires Each. (Trenton Iron Works.) 

IRON. 



a 

H 


53 

s 


CD 
O 

£<B 


Weight per Ft. 
in Lbs. Rope 
with Hemp 
Center. 


00 
5 

|'gi 

Woe 


Proper Work- 
ing Load in 
Tons of 2000 
Lbs. 


Circumference 
of new Manila 
Rope of Equal 
Strength. 


Minimum Size 
of Drum or 

Sheave in 
Feet. 


1 


21 


6f 


8.00 


74 


15 


14 


13 


2 


2 


6 


6.30 


65 


13 


13 


12 


3 


H 


54 


5.25 


54 


11 


12 


10 


4 


1* 


5 


4.10 


44 


9 


11 


84 


5 


14 


4| 


3.65 


39 


8 


10 


7* 


5* 


if 


4f 


3.00 


33 


64 


9h 


7 


6 


H 


4 


2.50 


27 


5* 


84 


64 


7 


14 


3^ 


2.00 


20 


4 


74 





8 


l 


31 


1.58 


16 


3 


6i 


51 


9 


i 


2f 


1.20 


11.50 


91 


5* 


44 


10 


21 


0.88 


8.64 


If 


4f 


4 


101 

104 


1 


2 


0.60 


5.13 


11 


3f 


34 


* 


8 


0.44 


4.27 


3 

i 


34 




10J 


0.35 


3.48 


3 


21 


10a 


-'i 


if 


0.29 


3.00 


1 


2| 


2 


10| 


H 


0.26 


2.50 


i 


2i 


14 



OAST STEEL. 



1 


21 


6f 


8.00 


155 


31 


A 


84 


2 


9 


6 


6.30 


125 


25 




8 


3 


1# 


54 


5.25 


106 


21 




71 


4 


It 


5 


4.10 


86 


17 


15 


61 


5 


U 


4f 

4f 


3.65 


77 


15 


14 


5| 


54 


If 


3.00 


63 


12 


13 


54 


6 


11 


4 


2.50 


52 


10 


12 


5 


7 


14 


34 


2.00 


42 


8 


11 


44 


8 


1 


34 


1.58 


33 


6 


94 


4 


9 


1 


2| 


1.20 


25 


5 


84 


34 


10 


s 


21 


0.88 


18 


34 


7 


3 


101 


ft 


2 


0.60 


12 


24 


5| 


21 


104 


9 


If 


0.44 


9 


14 


5 


11 


10f 


I 


14 


0.35 


7 


1 


44 


14 


10a 


a 


If 


0.29 


5i 


1 


3f 


11 


log 


11 


0.26 


44 


* 


34 


1 



STEAM BOILEKS. 829 



STEAM. 

STEAM BOILERS. 

Points to Remember in Selecting- a Boiler. 

(a) Suitability of furnace and boiler to kind of fuel. 
(6) Efficiency as to evaporative results. 

(c) Rapidity of steaming including 

(I.) Water capacity for given power. 
(II.) Water surface for given power. 

(d) Steam keeping qualities. 

(e) Safety from explosion. 
(/) Floor space required. 

(g) Portability, and ease with which boiler can be removed when old, for 
replacement by a new boiler. 

(h) Amount of, ease of, and rapidity of repairs. 

(i) Simplicity and fewness of parts. 

(?) Ability to stand forcing in case of necessity. 
* (k) Price, including cost of freight and setting. 

(I) Durability and reliability, 
(m) Ease of cleaning and inspection both inside and outside. 

(n) Freedom from excessive strains due to unequal expansion and ability 
to withstand same. 

(o) Efficient natural circulation of water. 
(p) Absence of joints or seams where flames may impinge. 

For central stations it is necessary to arrange for a number of boilers 
rather than one or two large ones. The size of unit adopted will depend 
to some extent on the character of the expected load diagram. With a 
number of boilers the cost of the reserve plant is reduced, though beyond, 
say six, there is less object in increasiug the number on this account. 

Types. 

Horizontal Return Tubular. — More generally used in United 
States than any other. Fire first passes under the shell, returns to front 
through tubes, thence up the chimney, except in some cases gases are again 
returned over top of the shell. Limited as to size and pressures carried by 
reason of external tiring. 

TO^ater-tube. — Very largely used where high steam pressures or 
safety from explosion are desirable. Fire passes about the exterior of tubes 
and in most cases under about one-half the circumference of the steam 
drums. Can be built for any size or pressure. Tubes are generally placed 
in a slanting position, from one set of headers to another, as in the Babcock 
& Wilcox, Heine & Co. ; or vertically, as in the Sterling and Cahall. 

Vertical E'ire Tube Used considerably in New England. Spe- 
cial design by Captain Manning; tubes 15 feet long 2£ inches diameter, 
arranged in vertical shell with large combustion chamber surrounded by a 
Avater leg. Cases mingle in combustion chamber, and in passing through the 
long narrow tubes give up nearly all the heat, practicably leaving flue gases 
450° to 500° F. By controlling height of water, steam can be superheated. 
Can be built for high pressures and of large size. 

ai, ii°** c ^- i r J?tarin e Boilers. — Not much used for electrical purposes, 
bneii of thick material, short in length and large in diameter. Furnaces 
internal, with return tubes from combustion chamber to uptake. 
i m Sf are the cylinder boiler, of small diameter and considerable 
lengtn (M to 35 feet). Fired externally, and gases pass under full length to 
cnimney. Flue boiler, has two or three large tubes running full length of 
shea, which is long and of small diameter. Fired externally under the shell, 
gases return through the flues to uptake. Neither of these types is now 
used for electrical purposes. 

The Horse-Power of Steam Boiler. 

The committee of the A. S. M. E. on " Trials of Steam Boilers in 1884" 
(Trans., vol. vi. p. 265), discussed the question of the horse-power of boilers : 



830 STEAM. 

The Committee) A.S.M.E. see Trans, vol. xxi.) approves the conclusions of 
the 1885 Code to the effect that the standard" unit of evaporation" should 
be one pound of water at 212° F. evaporated into dry steam of the same, 
temperature. This unit is equivalent to 965.7 British thermal units. 

The committee recommends that, as far as possible, the capacity of a 
boiler be expressed in terms of the " number of pounds of water evaporated 
per hour from and at 212°." It does not seem expedient, however, to aban- 
don the widely recognized measure of capacity of stationary or land boilers, 
expressed in terms of " boiler horse-power." 

The unit of commercial boiler horse-power adopted by the Committee of 
1885 was the same as that used in the reports of the boiler tests made at the 
Centennial Exhibition in 1876. The Committee of 1885 reported in favor of 
this standard in language of which the following is an extract : 

" Your Committee, after due consideration, has determined to accept the 
Centennial standard, and to recommend that in all standard trials the com- 
mercial horse-power be taken as an evaporation of 30 pounds of water per 
hour from a feed-water temperature of 100° F. into steam at 70 pounds gauge 
pressure, which shall be considered to be equal to 34|- units of evaporation ; 
that is, to 34£ pounds of water evaporated from a feed-water temper- 
ature of 212° F. into steam at the same temperature. This standard is 
equal to 33,305 thermal units per hour." 

The present Committee accepts the same standard, but reverses the order' 
of two clauses in the statement, and sligbtly modifies them to read as follows : 

The unit of commercial horse-power developed by a boiler shall be taken 
as 34£ units of evaporation per hour ; that is, 34£ pounds of water evaporated 
per hour from a feed-water temperature of 212° F. into dry steam of the 
same temperature. This standard is equal to 33,317 British thermal units 
per hour. It is also practically equivalent to an evaporation of 30 pounds 
of water from a feed-water temperature of 100° F. into steam at 70 pounds 
gauge pressure.* 

The Committee also indorses the statement of the Committee of 1885 con- 
cerning the commercial rating of boilers, changing somewhat its wording, so 
as to read as follows : 

A boiler rated at any stated capacity should develop that capacity when 
using the best coal ordinarily sold in the market where the boiler is located, 
when fired by an ordinary fireman, without forcing the fires, while exhibit- 
ing good economy; and, further, the boiler should delelop at least one- 
third more than the stated capacity when using the same fuel and operated 
by the same fireman, the full draft being employed and the fires being 
crowded ; the available draft at the damper, unless otherwise understood, 
being not less than £ inch water column. 

Heating- Surface of Boilers. 

Although authorities disagree on what is to be considered the heating 
surface of boilers, it is generally taken as all surfaces that transmit heat 
from the flame or gases to the water. The outside surface of all tubes is 
used in calculations. 

Kent gives the following rule for finding the heating surface of 

Vertical Tubular Boilers. — Multiply the circumference of the fire- 
box (in inches') by its height above the grate. Multiply the combined circum- 
ference of all the tubes by their length, and to these two products add the area 
of the lower tube sheet ; from this sum subtract the area of all the tubes, 
and divide by 144 : the quotient is the area of heating surface in square feet. 

Horizontal Beturn Tnlmlar Boilers. — (Christie). Multiply the 
length of that part of circumference of the shell (in inches) exposed to the 
fire by its length ; multiply the circumferences of the tubes by their num- 
ber, by their length in inches ; to the sum of these products add two-thirds 
of the area of both tube sheets less twice the area of tubes, and divide the 
remainder by 144. The result is the herting surface in square feet. 

Heating* Surface of Tillies. — Multiply the number of tubes by the 
diameter of a tube in inches, by its length in feet, and by .2618. The diam- 
eter used should be that of the fire side of the tube. 

* According to the tables in Porter's Treatise on the Richards Steam En- 
gine Indicator ; an evaporation of 30 pounds of water from 100° F. into steam 
at 70 pounds pressure is equal to an evaporation of 34.488 pounds from and 
at 212° ; and an evaporation of 34\ pounds from'and at 212° F. is equal to 
30.010 pounds from 100° F. into steam at 70 pounds pressure. 

The "unit of evaporation" being equivalent to 965.7 thermal units, the 
commercial horse-power = 34.5 x 965.7 = 33,317 thermal units, 



STEAM BOILERS. 



831 



Heating* Surface per Morse-power. — There is little uniformity 
of practice among builders as to the amount of heating surface per horse- 
power, but 12 square feet may be taken as a fair average. Babcock & Wil- 
cox ordinarily allow 10 square feet, but usually specify the number of 
square feet of heating surface. The Heine Boiler Company allow lh square 
feet, and the water-tube type in general will develop a horse-power for that 
amount of surface. 

Specifications for boilers should always clearly state the amount of heating 
surface required. 

Grate Surface. — The amount of grate surface per horse-power varies 
with the character of fuel tised and the draught that is available. With 
good quality of coal about equal results can be obtained with strong draught 
and small grate surface, and with large grate surface and light draught. 
Pittsburg coal gives best results Avith strong draught and a small grate sur- 
face. The following table shows the usual requirements, but in general 
grate surface should be liberal in size, and a rate of combustion of about 
10 lbs. per hour will be found good practice. 

Orate Surface per Horse-Power. (Kent.) 







on s 
5 &% 


Pounds of Coal bui-ned per square foot 






of Grate per hour. 




8 


10 


i?, 


15 


20 25 


30 


35 


40 




h^=H<N 






















vt 


3.45 


Square Feet Grate per H.P. 


Good coal and 


.43 


.35 


.28 


.23 


.17 


.14 


.11 


.10 


.09 


boiler . . . 


3.83 


.48 


.38 


.32 


.25 


.19 


.15 


.13 


.11 


.10 


Fair coal or 
boiler . . . 


( 8.61 


4. 


.50 


.40 


.33 


.26 


.20 


.16 


.13 


.12 


.10 


8 


4.31 


.54 


.43 


.36 


.29 


.22 


.17 


.14 


.13 


.11 


( 7 


4.93 


.62 


.49 


.41 


.33 


.24 


.20 


.17 


.14 


.12 


Poor coal or 
boiler . . . 


( 6.9 
6 


5. 
5.75 


.63 

.72 


.50 

.58 


.42 

.48 


.34 

.38 


.25 

.29 


.20 
.23 


.17 
.19 


.15 
.17 


.13 
.14 


( 5 


6.9 


.86 


.69 


.58 


.46 


.35 


.28 


.23 


.22 


.17 


Lignite and 
poor boiler . 


{ 3.45 


10. 


1.25 


1.00 


.83 


.67 


.50 


.40 


.33 


.29 


.25 



Area of Oas-Passag-es and flues. 

This is commonly stated in a ratio to the grate area. Mr. Barrus says the 
highest efficiency for anthracite coal, when burning 10 to 12 lbs. per square 
foot of grate per hour, is with tube area a to ^ of grate surface ; and for soft 
coal the tube area should be ^ to \ of the grate surface. 

Other rules in common use are to make the area over bridge walls (for 
horizontal return tubular boilers) \ the grate surface ; tube area \ and chim- 
ney area \. 

Air-space in Orates. — Usual practice is 30% to 50% area of grate for 
air space. If fuel clinkers easily, use the largest air space available. With 
coal free from clinker smaller air space may be used. 

Distance between Under Side of Boiler and Top of Orate. 

(For Horizontal Tubular Boiler.) 
For anthracite coal this should be 24 inches for the larger sizes, and can 
be 20 inches for the smaller sizes, such as pea, buckwheat, and rice. For 
bituminous coals non-caking, the grate should be about 30 inches below the 
boiler, and for fatty or gaseous coals from 36 to 48 inches. For average 
bituminous coals the distance can be 36 inches. Anthracite and bituminous 
coals cannot be economically burned in the same furnace. 

Steani Boiler Efficiency. 

The ratio of the heat units utilized in making steam in a boiler, to the 
total heat units in the coal used is called the efficiency of the boiler, and is 



832 



STEAM. 



rated in per cent. For example, the heating value of good anthracite coal 
is about 14.500 B. X. U., and will evaporate from and at 212° 15 lbs. water 
(14,500 4- 966). If a boiler under test evaporates 12 lbs. water per pound of 

12 x 100 
combustible, the efficiency will be — — = 80%, a figure not often ob- 
tained, but possible under special conditions. The heating value of bitumi- 
nous coals varies so much that it is necessary to determine it by a coal 
calorimeter before it is possible to determine the boiler efficiency. 

Strength of Riveted Shell. 

(Abridged from Barr on " Boilers and Furnaces.") 
Wrought-iron boiler-plates should average 45,000 lbs., and mild steel 55,000 
lbs., tensile strength per square inch of section ; but the gross strength of 
plate is lessened by the amount which has been taken out of it for the inser- 
tion of rivets. 

The following tables give the calculated working pressure for double- 
riveted and triple-riveted lap joints, and for butt-joints triple riveted, the 
factor of safety being 5. The rule for calculating the safe working pressure 
is : Multiply together the tensile strength of the plate, the thickness of the 
plate in parts of an inch, and the efficiency of the joint (see Riveting) ; divide 
the product by one-half the diameter of the boiler multiplied by the factor 
of safety. 

Working- Pressure for Cylindrical Shells of Steam Boilers. 

Factor of Safety, 5. (Barr.) 







Lap- Joints, Doubh 


-Riveted. 


Lap-Joints, Triple 


-Riveted. 




Thick- 














Diam- 


ness in 














eter 


16ths 


Iron 


Steel 


Steel 


Iron 


Steel 


Steel 


Inches. 


of an 


Shell, 


Shell, 


Shell, 


Shell, 


Shell, 


Shell, 




Inch. 


Iron 


Iron 


Steel 


Iron 


Iron 


Steel 






Rivets. 


Rivets. 


Rivets. 


Rivets. 


Rivets. 


Rivets. 


36 


4 


91 


Ill 


Ill 


100 


121 


123 


5 


112 


128 


137 


124 


139 


151 


40 


4 


82 


100 


100 


90 


109 


110 


5 


101 


115 


123 


112 


125 


136 


44 


4 


74 


91 


91 


83 


99 


100 


5 


91 


105 


112 


101 


114 


124 


48 


5 


84 


96 


102 


93 


104 


114 


6 


99 


107 


121 


110 


118 


135 


52 


5 


77 


89 


95 


86 


96 


105 


6 


92 


99 


112 


102 


109 


124 


54 


5 


75 


85 


91 


83 


93 


101 


6 


88 


96 


108 


98 


105 


120 


56 


5 


72 


82 


88 


80 


89 


97 


6 


85 


92 


104 


95 


101 


116 


60 


5 


67 


77 


82 


74 


83 


91 


6 


79 


85 


97 


88 


95 


108 


62 


6 


77 


83 


94 


85 


92 


104 


7 


88 


92 


108 


98 


103 


120 


64 


6 


74 


81 


91 


83 


89 


101 


7 


86 


89 


105 


95 


100 


117 


66 


6 


72 


78 


88 


80 


86 


98 


7 


S3 


87 


102 


93 


97 


113 


68 


6 


70 


76 


86 


78 


84 


95 


7 


81 


80 


99 


90 


94 


110 


70 


6 


68 


74 


83 


76 


81 


92 


7 


78 


82 


96 


87 


91 


107 


72 


7 


76 


79 


93 


85 


89 


104 


8 


85 


89 


104 


97 


98 


117 



STEAM BOILERS. 



833 



Working- Pressure for Cylindrical Shells of 
Steam .Boilers. (Barr.) 

Butt Joints, Triple Riveted. Factor of Safety, 5. 



Diameter 


Thick- 
ness in 


Iron 

Shell, 


Steel 
Shell, 


Diam- 


Thick- 
ness in 


Iron 

Shell. 


Steel 
Shell, 
Iron or 

Steel 
Rivets. 


Inches. 


16ths of 
an inch. 


Iron 
Rivets. 


Iron or 

Steel 

Rivets. 


eter, 
Inches. 


16ths of 
an inch. 


Iron 
Rivets." 




4 


108 


134 




6 


83 


102 


36 


5 


135 


165 


70 


7 


97 


118 




6 


161 


197 


8 


110 


134 




4 


102 


127 




9 


123 


151 


38 


5 


12S 


156 




6 


80 


99 




6 


152 


187 


79 


7 


94 


115 




4 


97 


120 




8 


107 


131 


40 


5 


121 


148 




9 


120 


147 




6 


145 


178 




7 


90 


110 




4 


93 


115 


75 


8 


102 


125 


42 


5 


116 


141 


9 


115 


141 




6 


138 


169 




10 


128 


157 




4 


89 


109 




7 


87 


106 


44 


5 


110 


135 


78 


8 


99 


121 




6 


132 


161 


9 


111 


135 




4 


85 


105 




10 


123 


151 


46 


5 


106 


129 




8 


92 


112 




6 


126 


154 




9 


103 


126 




5 


101 


124 


84 


10 


115 


140 


48 


6 


121 


148 




11 


126 


158 




7 


141 


172 




12 


137 


167 




5 


97 


119 




8 


86 


105 


50 


6 


116 


142 




9 


96 


117 




7 


135 


165 


90 


10 


107 


131 




5 


93 


114 




11 


117 


143 


52 


6 


111 


137 




12 


128 


156 




7 


130 


159 




8 


80 


98 




5 


90 


110 




9 


90 


110 


54 


6 


107 


132 


96 


10 


100 


123 




7 


125 


153 




11 


110 


134 




5 


87 


106 




12 


120 


146 


56 


6 


103 


127 




8 


75 


92 




7 


121 


148 




9 


85 


104 




5 


84 


102 


102 


10 


94 


115 


58 


6 


100 


123 




11 


104 


127 




7 


117 


142 




12 


113 


138 




6 


97 


118 




8 


71 


87 


60 


7 


111 


138 




9 


80 


98 




8 


128 


157 


108 


10 


89 


109 




6 


93 


115 




11 


98 


120 


62 


7 


109 


133 




12 


107 


130 




8 


124 


152 




8 


68 


83 




6 


90 


111 




9 


76 


93 


64 


7 


106 


129 


114 


10 


84 


103 


8 


120 


147 




11 


93 


113 




9 


135 


165 




12 


101 


123 




6 


88 


108 




8 


64 


78 


66 


7 


102 


125 




9 


71 


88 




8 


117 


143 


120 


10 


80 


98 




9 


131 


160 




11 


88 


108 




6 


85 


105 




12 


96 


117 


68 


7 


99 


121 










8 


113 


138 












9 


127 


155 











g34 STEAM. 

Safe Working- Pressure for Shell Plate. 

U. S. Statutes. — 

d =z diameter of boiler in inches. 
P=z safe working pressure, lbs. per square inch. 
t = thickness of metal in inches. 
w = tensile strength of metal. 
k = factor of safety = 6 for U. S. and 4.5 for Great Britain. 

t X 2 X to 

P rr - — for single-riveted. For double-riveted, add 20%. 

ft X o 

Board of Trade. — 

w X B X * X 2 



d X k X 100 



where the notation is the same as in IT. S. rule, and B = percentage of 
strength of joint as compared with solid plate. 

Rules Governing- Inspection of Boilers in Philadelphia. 

In estimating the strength of the longitudinal seams in the cylindrical 
shells of boilers, the inspector shall apply two formula?, A and B : 

j Pitch of rivets — diameter of holes punched to receive the rivets _ 
' [ pitch of rivets 

percentage of strength of the sheet at the seam. 

!Area of hole filled by rivet X No. of rows of rivets in seam x shear- 
ing strength of rivet 
pitch of rivets X thickness of sheet x tensile strength of sheet 
percentage of strength of the rivets in the seam. 
Take the lowest of the percentages as found by formula? A and B, and 
apply that percentage as the " strength of the seam" in the following for* 
inula, C, which determines the strength of the longitudinal seams : 

( Thickness of sheet in parts of inch x strength of seam as obtained 

q ! by formula A or B x ultimate strength of i ron stamped on plates 

( internal radius of boiler in inches x 5 as a factor of safety 

safe working pressure. 

Safe Working Pressure for Flat Plates. 

U. S. Statutes. — 

P = safe working pressure. 
S = surface supported, square inches. 
t = thickness of metal in sixteenths of an inch. 

k = constant for plates of different thickness, and for various condi- 
tions. 
p = greatest pitch in inches. 

P 2 
K=. 112 for /g-inch plates and less, fitted with screw stay bolts and nuts, or 

plain bolt fitted with single nut and socket, or riveted head and 

socket, 
if = 120 for plates more than T 7 S inch thick, under same conditions. 
K=z 140 for flat surfaces where the stays are fitted with nuts inside and out. 
K= 200 for flat surfaces under same conditions, bnt with washer riveted to 

plate, washer to be one-half as thick as plate, and of a diameter | 

pitch. 



STEAM BOILERS. 335 

No brace or stay on marine boilers to bave a greater pitcb tban 10^ 
incbes on fire boxes and back connections. Plates fitted with double-angle 
irons riveted to plate, and with leaf at least two-thirds tbickness of plate, 
and deptb at least one-fourtb of pitcb, allowed tbe same pressure as plate 
witb wasber riveted on. 

Board, of Trade. — Using same notation as in U. S. rules : 

S — 6 

A"=:125 for plates not exposed to beat or flame, tbe stays fitted witb nuts 

and wasbers, tbe latter at least tbree times tbe diameter of tbe stay 

and f tbe tbickness of tbe plate ; 
A~=r: 187.5 for tbe same condition, but tbe wasbers f the pitcb of stays in 

diameter, and tbickness not less tban plate ; 
K = 200 for tbe same condition, but doubling plates in place of wasbers, tbe 

widtb of wbicb is § tbe pitch, and tbickness the same as the plate ; 
K— 112.5 for tbe same condition, but tbe stays Avitb nuts only ; 
A' = 75 when exposed to impact of heat or flame and steam in contact with 

the plates, and the stays fitted with nuts and washers three times 

the diameter of the stay, and § the plate's thickness ; 
K = 67.5 for the same condition, but stays fitted with nuts only ; 
A = 100 when exposed to beat or flame, and water in contact with the 

plates, and stays screwed into the plates, and fitted with nuts ; 
K— 66 for the same condition, but stays witb riveted heads. 

Ductility of Boiler Plate. — U. S. Inspectors of Steam Vessels. 

In test for tensile strength, sample shall show reduction of area of cross- 
section not less than tbe following percentages :* 

Iron. 

45,000 lbs. tensile strength and under 15 per cent. 

For each additional 1000 t. s. up to 55,000 t. e. add . 1 " 
55,000 lbs. tensile strength, and above .25 " 



Steel. 

All steel plates J inch thick and under 50 per cent. 

* to | inch 45 " 

inch and above ....... 40 " 



Boiler Head Stay*. 



I 



The United States Regulations on braces are : " No braces or stays here- 
after employed in the construction of boilers shall be allowed a greater 
strain than 6,000 lbs. per square inch of section. Braces must be put in suf- 
ficiently thick so that the area in inches which each has to support, multi- 
plied by the pressure per square inch, will not exceed 6,000 when divided by 
the cross-sectional area of the brace or stay. 

" Steel stay-bolts exceeding a diameter of 1 \ inches, and not exceeding a 
diameter of 1\ inches at tbe bottom of the thread may be allowed, a strain 
not exceeding 8,000 lbs. per square inch of cross-section ; steel stay bolts 
exceeding a diameter of 2h inches at bottom of thread may be allowed a 
strain not exceeding 9,000 lbs. per square inch of cross-section ; but no 
forged or welded steel stays will be allowed. 

"The ends of such stay may be upset to a sufficient thickness to allow 
for truing up, and including the depth of tbe thread. And all such stays 
after being upset, shall be thoroughly annealed." 



836 



STEAM. 



Direct Brac«N. — The following table is given by Mr. Wm.M, Barr 
in " Boilers and Furnaces," p. 122. The working strength assumes an ulti- 
mate strength of 6000 lbs. per square inch of section. 



Diam- 
eter of 


Wrought Iron 
Stays. 


Inches square each Brace will Support for 
Pressures per Square Inch. 


Brace 

Inches. 


Area 
sq. in. 


Working 
Strength 
Pounds. 


75 
Pounds. 


100 
Pounds. 


125 
Pounds. 


150 
Pounds. 


i 
1 

n 
n 


.60 

.78 

.99 

1.23 

1.48 

1.77 


3600 
4712 
5964 
7362 
8880 
10620 


7.0 
7.9 
8.9 
9.9 
10.7 
11.9 


6.0 
6.9 
7.7 
8.6 
9.5 
10.4 


5.4 
6.1 
6.9 

7.7 
8.5 
9.2 


4.9 
5.6 
6.4 
7.0 

7.7 
8.5 



Diagonal Braces. 

calculated separately. 



(" Boilers and Furnaces," p. 129.) These must be 



Let 



Then 



A = surface to be supported in square inches. 
B = working pressure in lbs. 
H= length of diagonal stay in inches. 

L =z length of line drawn at right angles from surface, to be sup- 
ported to end of diagonal stay in inches. 

£ — working stress per square inch on stay in lbs. 

a = area required for direct stay in square inches. 
a-. = area of diagonal stay in square inches. 

T= diameter of diagonal stay in square inches. 

a. = a x H-~ L ; 

H = a 1 x L -f- a. 



V .7854 V .7 



X Bx H. 



854 5 X L 



.7854 X T 2 X SXL 
AxH 



Boiler Setting*. 



Water tube and special types of boilers require special settings largely 
controlled by local conditions, location of flues, etc., and cannot be tabulated 
here. 

The setting of horizontal return tubular boilers has become so nearly 
standardized that the table following, taken in connection with the cuts, 
will give all the general dimensions of brick-work required. 

For all special boiler settings, furnaces, etc., the reader is referred to the 
makers of each. 



STEAM BOILERS. 



837 




Fig. 3. 



838 



STEAM. 



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oSpug; jo ssaujpmjx 



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uoijupimojj jo iijguaT; 



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^uoj j[ jo ssau>[opqx 



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OPTS 3 jo ssauipnqx 



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opisui jo ss9u>ioiqx 



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optsjno jo ssaa5[oii[x 



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»g 

a> 

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a 

f^ th n co io lo o » lo oo nco a a o o 

00 

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tc 

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q 



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N 


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<H HHHHHHrlrtrtHHHrtH 


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-4 






cm 


S8888S$S8g{2§§!§ 



STEAM BOILERS. 



839 





•3[0iia; 9ji^ jo -ojs[ 


650 
700 
725 
780 
800 
850 
910 
900 
1000 
1000 
1000 
1200 
1200 
1400 
1500 


•OUTT .IOO[£ 
9AOqi? 5[0Ijg UOUIIUOQ JO 'OJy[ 


6250 
7100 
8200 
8750 
9250 
10700 
11700 
14450 
17680 
16600 
17900 
19000 
19600 
21550 
22500 


bio 

.s 

03 
GO 


put? .i9[ioa uaaAvjaq aoudg 


N 


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840 



STEAM. 



The draught power op A chimney varies as the square root of the 
height. 

The retarding friction of the chimney may he taken as equivalent to a 
diminution of its actual area by a layer of gas two inches thick all the way 
around the perimeter of its flue. 

A = actual area of flue in square feet. 
E — effective area of flue in square feet. 
H= height in feet. 
D = diameter of flue in feet. 
D l = side of a square chimney equivalent to A. 
Then: E—A — 0.6 VZ. 

Z» 1= Vy£+4_inches. 
Horse-power = 3.33 E^ H. (3 ) 

The above formulae are by Kent, and are based on a consumption of 5 
lbs. coal per h. p. per hour. W. W. Christie, in a paper read before the 
A.S.M.E., Trans., vol. xviii., p. 387, gives as his opinion that all chimneys 
should be compared and rated by using coal capacity as a basis, not horse- 
power. In the following table, coal capacity can be found by multiplying 
h.p. by 4. 

Size of Chimneys for Steam-Boilers. 
(W. W. Christie.) 



(i) 

(2) 



© 












Height 


of Chimney. 










© 


50 
ft. 


60 
ft. 


70 

ft. 


80 
ft. 


90 
ft. 


100 

ft. 


110 
ft. 


125 

ft. 


150 
ft. 


175 

ft. 


200 
ft. 


225 
ft. 


250 

ft. 


300 

ft. 




Boiler Horse-power= 3.25 A^H; 4 lbs. of coal burned considered 1 H.P. 


18 
21 
24 

27 

30 
33 
36 
39 

42 
48 
54 
60 

66 

72 
78 
84 

90 

96 

102 

108 

114 
120 
132 
144 


4 2 

55 

72 
91 

114 


40 
62 
78 
101 

124 
149 
179 


4 9 

65 
85 
107 

133 
163 
192 

224 

263 


52 

68 
91 
114 

143 
172 
205 
241 

282 
364 


98 
124 

153 

182 
218 

257 

296 

387 
491 
605 


159 

192 

228 
270 

312 
410 
517 
637 

774 
920 


202 
241 
283 

332 

429 
543 
669 

809 
962 
1131 
1310 
















257 
302 

351 

458 
579 
715 

865 
1051 
1206 
1401 

1609 

1830 
2067 
2314 


























390 
510 

647 
797 

965 
1147 
1349 
1563 

1794 
2041 

2304 

2584 

2879 
3191 
3861 
4596 






















683 

845 

1021 
1215 
1459 
1654 

1898 
2161 

2434 
2734 

3045 
3374 

4082 
4859 










1092 
1300 
1524 
1768 

2031 
2311 

2607 
2925 

3257 
3611 
4368 
5200 


1378 
1619 

1875 

2155 
2451 
2766 
3101 

3455 
3829 

4631 
5515 


1706 
1976 

2269 
2584 
2915 
3269 

3643 
4037 
4882 
5811 


2165 

2486 
2831 
3195 
3578 

3991 
4420 
5350 
6367 



CHIMNEYS. 



841 



The following table* will prove useful to those having to do with electric 
installations, and gives the horse-power of chimneys to be used in power 
plants having very efficient engines, such as compound or triple expansion 
engines, when 2 lbs. of coal burned under the boiler produce one horse- 
power at the engine. 

Size of Chimney for Steam Boilers. 

(W. W. Christie.) 















Heig 


it of Chimney 










a 


50' 


60' 


70' 


80' 


90' 


100 


110' 


125' 


150' 


175' 


200' 


225' 


250' 


300' 




Horse-power = G.5 AS H. When 2 lbs. coal burned per hour = 1 H.P. 


18 
21 
24 

27 

30 
33 


84 
110 
144 

182 

228 


92 
124 
156 

202 

248 
298 
358 


98 
130 
170 
214 

286 
326 
384 
448 

528 


In. 

136 

1182 
228 

286 
344 
410 

4S2 

534 

728 


1 

1:: 

196 

248 

306 
364 
436 
514 

592 

774 

982 

1210 


i 

31S 
384 
456 
540 

624 

820 

1034 

1274 

1548 
1840 


1 

404 

482 
566 

662 

858 

1086 

1338 

1618 
1924 

2262 
2620 


1 














36 


514 

604 

702 

916 

1158 

1430 

1730 
2102 
2412 

2802 

3218 
3660 
4134 
4628 














39 














4? 


780 
1020 
1294 
1594 

1930 

2294 
26! IN 
3126 

3588 
4082 
4608 
5168 

5758 
6382 
7722 
9192 












48 












54 


1366 
1690 

2042 
2430 
2918 
3308 

3796 

4322 
4868 
5468 

6090 
6748 
8164 
9718 










fif) 










68 

72 
78 
84 

93 
93 
102 
103 

114 
120 
132 
144 


2184 
2600 
3048 
3536 

4062 
4622 
5214 
5850 

6514 

7222 
8736 
10400 


2756 
3238 
3750 

4310 
4902 
5532 
6202 

6910 

7658 
9262 
11030 


3412 
3952 

4538 
5168 
5830 
6538 

7286 
8074 
9764 
11622 


4330 

4972 
5662 
6360 
7156 

7982 
8840 
10700 
12734 



Chimney Construction. 

A brick chimney shaft is made up of a series of steps, each of which is of 
uniform thickness, but as we ascend each succeeding step is thinner than 
the one it rests upon. These bed joints at which the thickness changes are 
the joints of least stability. The joints and the one at the ground line 
are the only ones to which it is necessary to apply the formulas for deter- 
mining the stability of the stack. 

The height of the different steps of uniform thickness varies greatly, ac- 
cording to the judgment of the engineer, but 170 feet is, approximately, the 
extreme height that any one section should be made. This length is seldom 
approached even in the tallest chimneys, as the brick-work has to bear, in 
addition to its weight, that due to the pressure of the wind. The steps 
should not exceed about 90 feet, unless the chimney stack is inside a tower 
which protects it from the wind. In chimneys from 90 to 120 feet high the 
steps vary from 17 to 25 feet, the top step being one brick thick ; in chim- 

* "Chimney Design and Theory" W. W.Christie, D. VanNosirand Company, 



842 



STEAM. 



C.I.CAP % METAL 
4 SECTIONS 



12 CONCRETE! 





I^ttIJ? plan of brick chimney 

,i ^?|3,™ FOR M.H.BIRGE SON'S 
leAjih.™ WALL PAPER FACTORY 
!g3, oj 1 a NIAGARA & MARYLAND STS. 
[l flttl " fiREFN A WII-KB ] ARCHITECTS 
- A UT ! I « * ENGINEERS 

BUFFALO N.Y 



Fig. 4. 



CHIMNEYS. 



843 



neys from 130 to 150 feet the steps vary from 25 to 35 feet ; in chimneys from 
150 to 200 feet the steps vary from 35 to 50 feet ; in chimneys from 200 to 300 feet 
and over, the steps vary from 50 to 90 feet, the top step being one and one- 
half bricks thick. The outside dimensions of a chimney at the base should 
generally not be less than one-tenth of the height of the stack for square 
chimneys ; one-eleventh for octagonal, and one-twelfth for round. The bat- 
ter may be 2£ inches for every 10 feet. 

The foundation of a chimney is one of the most important points to be 
considered. When this is upon solid rock it is only necessary to excavate 
to a depth sufficient to prevent the heat of the gases from materially affect- 
ing the natural stone, and to secure the spread of the base. In cases where 
chimneys are to be built upon alluvial clays or made ground, it is necessary 
to excavate until a good stiff clay, hard sand, or rock bottom is reached. 
The excavation is filled with concrete in various ways, or filled according 
to the judgment of the engineer, so as to economize material without en- 
dangering the structure. 

Babcock and Wilcox give the following formula for the ability of brick 
chimneys to withstand wind pressure. 
w = weight of chimney in lbs. (brickwork = 100 to 130 lbs. per cubic foot.) 
d = average diameter'in feet, or width if square. 
h = height in feet. 
b =z width of base. 

A; = constant, for square chimneys = 56. 

for round chimneys = 28. 

for octagonal chimneys = 35. 

, dh* . . dW- 

c = fc and w = k — =— . 

w b 

Thin Shell Brick Chimneys. — While the steel-plate lined stack 
is considerably cheaper than the ordinary heavy brick chimney, there is a 
design of brick chimney used by Messrs. Green & Wicks, architects, of 
Buffalo, N. Y., that has all the durability of the brick stack, and costs less 
than one of the same capacity in steel plate. The bricks must all be spe- 
cially selected, hard burned, laid in rich Portland cement. By courtesy of 
the architects Ave are able to show drawings of such a chimney, that was 
erected by them for a wall-paper factory in Buffalo, and which has success- 
fully withstood the most severe winds of the region (Figs. 4 and 5). 

Note on Thin Shell Brick Chimneys. — The fire-brick core must be kept 
free from the outer shell, not being tied or bonded to it in any manner. 
The bricks are circular, with inside diameter laid up to 4 feet. 

The galvanized iron-wire cables shown in the plans are for lightning protec- 
tion. They are soldered and bolted to the iron cap, and after passing 
down through staples built into the walls for the purpose, are grounded on 
20-oz. copper plates 3 feet by 1| feet, set on edge ten feet away from the 
foot of the stack. The cables are to be soldered and riveted to the plates, 
and all the plates must be connected together by a f-inch galvanized iron 
cable soldered to all the plates, 
The chimney shown in the plans cost about $2,000, and can be built for 



BOTTOM 3 10% 
TOP 3'l01£ 




Fig. 5 



"PLAN AND SECTION 

SHOWING LOCATION 

OF CHIMNEY 

BIRGE FACTORY 



844 



STEAM. 



Draft Power for Combustion of fuels. 

(R. H, Thurston.) 





Draft of Chim- 




Draft in Ins. 
of Water. 


Fuel. 


ney in Inches 
of Water. 


FueL 


Wood 


0.20 to 0.25 


Coal-dust 


0.80 to 1.25 


Sawdust ..... 


0.35 " 0.50 


Semi Anthracite coal 


0.90 " 1.25 


Sawdust mixed with 
small coal .... 


0.60 " 0.75 


Mixture of breeze and 
slack , 


1.00 " 1.33 


Steam coal .... 


0.40 " 0.75 


Anthracite .... 


1.25 " 1.50 


Slack, ordinary . . 


0.60 " 0.90 


Mixture of breeze and 
coal-dust .... 


1.25 " 1.75 


Slack, very small . . 


0.75 " 1.25 


Anthracite slack . . 


1.30 " 1.80 



Height of Chimney for Burning- Given Amount!* of Coal. 

Professor Wood (Trans. A. S. M. E., vol. xi.) derives a formula from 
which he calculates the height of chimney necessary to burn stated quan- 
tity of coal per square foot of grate per hour, for certain temperatures of 
the chimney gas. 







Pounds of Coal per Square Foot Grate Area. 


Temp. 


Absolute 




Outside 


Temp. Chim- 


16 20 24 


Air. 


ney Gases. 










Height of Chimney, Feet. 




700 


67.8 


157.6 


250.9 




800 " 


55.7 


115.8 


172.4 


o-^ 


1000 


48.7 


100.0 


149.1 




1100 


48.2 


98.9 


148.8 


1200 


49.1 


100.9 


152.0 


n "3 


1400 


51.2 


105.6 


159.9 


iO o 


1600 


53.5 


110.9 


168.8 


2000 


63.0 


132.2 


206.5 



Rate of Comoustioii Due to Height of Chimney. 

Prof. Trowbridge (" Heat and Heat Engines," p. 153) gives the following 
table, showing the heights of chimneys for producing certain rates of com- 
bustion per square foot of area of section of the chimney. The ratio of the 
grate to the chimney section being 8 to 1. 





Lbs. Coal 


Lbs. Coal 

burned per 

Hour per 

sq. ft. of 

Grate. 




Lbs. Coal 






burned per 




burned per 


Lbs. Coal 


Height 


Hour per 


Height in 


Hour per 


burned per 


in Feet. 


sq. ft. of 


Feet. 


sq. ft. Sec- 


Hour per 




Section of 




tion of 


sq. ft. Grate. 




Chimney. 




Chimney. 




25 


68 


8.5 


70 


126 


15.8 


30 


76 


9.5 


75 


131 


16.4 


35 


84 


10.5 


80 


135 


16.9 


40 


93 


11.6 


85 


139 


17.4 


45 


99 


12.4 


90 


144 


18.0 


50 


105 


13.1 


95 


148 


18.5 


55 


111 


13.8 


100 


152 


19.0 


60 


116 


14.5 


105 


156 


19.5 


65 


121 


15.1 


110 


160 


20.0 



CHIMNEYS. 



845 



Dimensions and Cost of ISrick Chimneys. 

(Buckley.) 



O 


fa 


fa 




Outside "Wall. 


Oh 

'u be 




o >> 


* a> 


'5 


^3 
32 

S 


■a a & 

O'te 




fat 

to S 

1-1 


O cS 

"S 3 

G'O 

Ofa 


O 2 


< 


No. 
Brick. 


Cost® 

|14 per 

M. 


a 3 
o!3 

HO 


85 


80 


25 in. 


7 ft. 5 in. 


32,000 


.$ 448.00 


$ 60.00 


$ 90.00 


$ 598.00 


135 


90 


30 in. 


8 " 3 " 


40,000 


560.00 


82.00 


144.00 


786.00 


200 


100 


35 in. 


9 "10 " 


65,000 


910.00 


118.00 


198.00 


1,226.00 


300 


110 


43 in. 


10 " 2 " 


75,000 


1,050.00 


190.00 


252.00 


1,492.00 


450 


120 


51 in. 


11 " 2 " 


87,000 


1,218.00 


261.00 


306.00 


1,785.00 


750 


130 


61 in. 


12 " 6 " 


131,000 


1,834.00 


334.00 


360.00 


2,528.00 


1000 


140 


74 in. 


13 " 11 " 


151,000 


2,114.00 


432.00 


414.00 


3,060.00 


1650 


150 


88 in. 


15 " 1 " 


200.000 


2,800.00 


482.00 


468.00 


3,750.00 


2500 


160 


110 in. 


17 " 10 " 


275,000 


3,850.00 


720.00 


525.00 


5,095.00 



Steel Rlate Chimneys have long been used in the iron and coal re- 
gions, but have only recently come into use in the East, except in the old 
style thin sheet iron guyed stack, which lasts but a short time. 

Many of the manufacturers of steel structures are now erecting very sub- 
stantial steel-plate stacks lined Avith fire bricks, that are of artistic outline, 
strong, and when kept well painted are durable and need no guys, as they 
are spread at the base, and bolted to a heavy foundation. They are usually 
designed to stand a wind pressure of 50 lbs. per square foot. 

Sizes of Foundations for Steel Chimney. 

(Selected from Circular of Philadelphia Engineering Works.) 
Half-Lined Chimneys. 



Diameter, clear, feet . . 

Height, feet 

Least diameter foundation 
Least depth foundation . 

Height, feet 

Least diameter foundation 
Least depth foundation . 



3 


4 


5 


s 


7 


9 


100 


100 


150 


150 


150 


150 


15'9" 


16'4" 


20'4" 


21 / 10 / 


22 / 7 // 


23'8'- 


6' 


6' 


9' 


8' 


9' 


10' 




125 


200 


200 


250 


275 




18'5" 


23'8" 


25' 


29'8'- 


33'6" 




. 7 ' 


10' 


10' 


12' 


12'' 



11 

150 
24'8" 
10' 
300 
36' 
14' 



Brick lining- for Steel Stacks. 

Allowing 1| inches air space between stack and lining : 

Bricks 8J X 4 X 2 inches, laid without mortar ; 
Lining S\ inches (one brick) thick ; 

Number of bricks per foot in diameter of stack, and per foot of height 
= 47. 



Allowing 1 inch air space between stack and lining : 

Bricks 8J X 4 X 2 inches, laid without mortar ; 
Lining 4 inches (one brick) thick ; 

Number of bricks per foot in diameter of stack, and per foot of height 
= 25. 



846 



FtTEli. 



Dimension!) and Cost of Iron Stacks. (Guyed.) 
(Buckley.) 



Horse- 


Height, 


Diameter, 


Number of 


Price Stack 


Price 


Power. 


Feet. 


Inches. 


Iron. 


Complete. 


per Foot. 


25 


40 


16 


12 and 14 


$ 61.00 


$ 1.52 




40 


18 


12 and 14 


71.00 


1.78 




50 


18 


12 and 14 


84.00 


1.68 


'75' 


50 


20 


12 and 14 


87.00 


1.75 




50 


26 


12 and 14 


105.00 


2.10 




60 


22 


12 and 14 


111.00 


1.85 


lOO* 


60 


24 


12 and 14 


125.00 


2.08 




60 


26 


12 and 14 


133.00 


2.22 




60 


28 


12 and 14 


148.00 


2.45 


125 


60 


28 


10 and 12 


190.00 


3.18 




60 


32 


10 and 12 


203.00 


3.38 


'l50' 


60 


34 


12 and 14 


165.00 


2.75 


200 


60 


36 


10 and 12 


215.00 


3.58 


225 


60 


38 


10 and 12 


228.00 


3.80 


250 


60 


42 


10 and 11 


257.00 


4.28 


300 


60 


46 


10 and 12 


286.00 


4.76 


400 


60 


52 


10 and 12 


340.00 


5.66 



For general details of construction of the various types of chimneys used 
in the U. S. the reader is referred to " Chimney Design and Theory," by 
W. Wallace Christie, published by D. Van Nostrand Co. 

FUEL. 

Kinds and Ingredients of Fuels. 

The substances which we call fuel are : wood, charcoal, coal, coke, peat, 
certain combustible gases, and liquid hydrocarbons. 

Combustion or burning is a rapid chemical combination. 

The imperfect combustion of carbon produces carbonic oxide (CO), and 
carbonic acid or dioxide (C0 2 ). 

From certain experiments and comparisons Rankine concludes " that tbe 
total heat of combustion of any compound of hydrogen and carbon is nearly 
the sum of the quantities of heat which the hydrogen and carbon contained 
in it would produce separately by their combustion (CH 4 — marsh gas or 
fire-damp excepted)." 

In computing tbe total heat of combustion of a compound, it is conven- 
ient to substitute for the hydrogen a quantity of carbon which would give 
the same quantity of heat ; this is accomplished by multiplying the weight 
of hydrogen by 62032 -J- 14500 = 4.28. 

From experiments by Dulong, Despretz, and others, " when hydrogen and 
oxygen exist in a compound in the proper proportion to form water (by 
weight nearly 1 part H to 8 parts O), these constituents have no effect on 
the total heat of combustion. 

" If hydrogen exists in a greater proportion, take into the heat account 
only the surplus." 

Dulong's formula for the total heat of combustion of carbon, hydrogen, 
oxygen, and sulphur, where C, H, O, and S refer to the fractions of one 
pound of the compound, the remainder being ash, etc. Let h =z total heat 
of combustion in B.T.U. per pound of compound. 



h = 14600 C+ 62000 



("-§: 



-f 4000 S. (A.S.M.E. Trans, vol. xxi.) 



Rankine says : " The ingredients of every kind of fuel commonly used may 
be thus classed : (1) Fixed or free carbon, 'which is left in the form of char- 
coal or coke after the volatile ingredients of the fuel have been distilled 
away. These ingredients burn either wholly in the solid state, or part in 
the solid state and part in the gaseous state, the latter part being first 
dissolved by previously formed carbonic acid. 

"(2) Hydrocarbons, such as olefiant gas, pitch, tar, naphtha, etc., all of 
which must pass into the gaseous state before being burned. 



FUEL. 



847 



" If mixed on their first issuing from amongst the burning carbon with a 
large quantity of air, these inflammable gases are completely burned with 
a transparent blue flame, producing carbonic acid and steam. When raised 
to a red heat, or thereabouts, before being mixed with a sufficient quantity 
of air for perfect combustion, they disengage carbon in fine powder, and 
pass to the condition partly of marsh gas, and partly of free hydrogen ; and 
the higher the temperature, the greater is the proportion of carbon thus 
disengaged. 

" If the disengaged carbon is cooled below the temperature of ignition be- 
fore coming in contact with oxygen, it constitutes, while floating in the gas, 
smoke, and when deposited on solid bodies, soot. 

" But if the disengaged carbon is maintained at the temperature of ignition, 
and supplied with oxygen sufficient for its combustion, it burns while float- 
ing in the inflammable gas, and forms red, yellow, or white flame. The 
flame from fuel is the larger the more slowly its combustion is effected. 

" (3) Oxygen or hydrogen either actually forming water, or existing in com- 
bination with the other constituents in the proportions which form water. 
Such quantities of oxygen and hydrogen are to be left out of account in de- 
termining the heat generated by the combustion. If the quantity of water 
actually or virtually present in each pound of fuel is so great as to make its 
latent heat of evaporation worth considering, that heat is to be deducted 
from the total heat of combustion of the fuel. The presence of water or its 
constituents in fuel promotes the formation of smoke, or of the carbona- 
ceous flame, which is ignited smoke, as the case may be, probably by 
mechanically sweeping along fine particles of carbon. 

" (4) Nitrogen, either free or in combination with other constituents. This 
substance is simply inert. 

" (5) Sulphuret of iron, which exists in coal and is detrimental, as tending to 
cause spontaneous combustion. 

" (6) Other mineral compounds of various kinds, which are also inert, and 
form the ash left after complete combustion of the fuel, and also the clinker 
or glassy material produced by fusion of the ash, which tends to choke the 
grate." 

Total Heat of Combustion of Fuels. (D. K. Clark.) 

The following table gives the total heat evolved by combustibles and their 
equivalent evaporative power, with the weight of oxygen and volume of air 
chemically consumed. 



Combustibles. 



<h<2o 



lbs. 



Quantity of Air 
Consumed per 
Pound of Com- 
bustible. 



lbs. 



Cu. Ft. 
at 62°F. 



O OH 






III- 



Hydrogen 

Carbon making CO ...... 

Carbon making C0 2 

Carbonic oxide 

Light Carbureted Hydrogen . . 

Olefiant Gas 

Coal (adopted average desiccated) 
Coke(adopted average desiccated) 

Lignite, perfect 

Wood, desiccated 

Wood, 25 per cent moisture . . 

Petroleum 

Petroleum oils 

Sulphur 



8.0 

1.33 

2.66 

0.57 

4.00 

3.43 

2.45 

2.49 

2.04 

1.40 

1.05 

3.29 

4.12 

1.00 



34.8 
5.8 
11.6 
2.48 
17.4 
15.0 
10.7 
10.81 
8.85 
6.09 
4.57 
14.33 
17.93 
4.35 



457 
76 
152 
33 
229 
196 
140 
142 
116 



235 
57 



62000 

4452 
14500 

4325 
23513 
21343 
14700 
13548 
13108 
10974 

7951 
20411 
27531 

4000 



64.20 

4.61 
15.00 

4.48 
24.34 
22.09 
15.22 
14.0? 
13.57 
11.36 

8.20 
21.13 
28.50 

4.17 



848 



STEAM. 



Ill* 



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cn -f o t- r. -e « o 

■*-<*"*O00«Dc6'<* 



•8[qijsnquioQ 'q\ X qjiAV 
oSIS J13 puis uio.ij xiajt/jo 
-dtjA8 aaj^VL J° spimoj uj 



CI t- 

S3 



© © O LO O LO o o 
o q a ri o ci c co 
lo © lo ci o l- t- id 



■aiq^snquioo 
jo punoj .i8d x pasrea 
JSJ^Al jo spuno'j uj 



O t- O ifl © O LO o 

i- co co -t o c -r o 
CO co © t- o © ci © 
W LO LO h cs t- c~ US 



\uy 

jo A'tddng x^oi^aaoaqx 
oqj seiuix aaJRX l H!Ai 



\ny jo A^ddng x 1301 
-jajosqx sqj eoiAvx mFM 



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ury jo A"[ddng j^oijaj 
-oaqX 9RJ S91UJX f I q?LM. 



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■*rv jo 

A^ddng xeoijejoaqx qi!A\ 






•8[qi!»snquioo 
jo punoj ja j spunod uj 







FUEL. 



849 



Temperature of Fire. 

By reference to the table of combustibles, it will be seen that the temper- 
ature of the fire is nearly the same for all kinds of combustibles, under sim- 
ilar conditions. If the temperature is known, the conditions of combustion 
may be inferred. The following table, from M. Pouillet, will enable the 
temperature to be judged by the appearance of the fire : 



Appearance. 


Temp. F. 


Appearance. 


Temp. F. 


Red, just visible . . 

" dull 

" cherry, dull . . 

full . . 

" " clear . 


977° 
1290 
1470 
1650 
1830 


Orange, deep . . . 

" clear . . . 

White heat .... 

bright . . . 

" dazzling . . 


2010 
2190 
2370 
2550 
2730 



To determine Temperature U.v fusion of Metals, etc. 



Substance. 


Tern. F. 


Metal. 


Tem. F. 


Metal. 


Tem. F. 


Tallow . . . 
Spermaceti . 
Wax, white . 
Sulphur . . 
Tin .... 


92° 
120 
154 
239 
455 


Bismuth . 
Lead . . . 
Zinc . . . 
Antimony . 
Brass . . 


518° 
630 
793 
810 
.1650 


Silver, pure . . 
Gold, coin . . 
Iron, cast, med. 
Steel .... 
Wrought iron . 


1830° 

2156 

2010 

2550 

2910 



American Woods. 



Kind of Wood. 



Hickory — Shell bark. 
White oak .... 
Hickory — Bed heart 
Southern pine . . . 

Red oak 

Beech 

Hard maple . . . 
Virginia pine . . . 

Spruce 

New Jersey pine . . 

Yellow pine . . . 
White pine .... 



Weight 
per Cord. 



4469 
3821 
3705 
3375 
3254 
3126 
2878 
2680 
2325 
2137 

1904 

1868 



Value in Tons Coal. 



Anthracite Bituminous 



.608 

.52 

.504 

.459 

.443 

.425 

.391 

.364 

.316 

.291 

.259 

.254 



.563 

.481 

.467 

.425 

.41 

.394 

.363 

.338 

.293 

.269 

.24 
.235 



_l 



850 



STEAM. 
American Coals. 



State. 



Coal. 
Kind of Coal. 



Pennsylvania. Anthracite 



Cannel . . . 
Connellsville . 



Kentucky. 



Illinois. 



Indiana. 



Semi-bituminous 
Stone's Gas . 
Youghiogheny 
Brown . . . 
Coking . . . 



Cannel 



Lignite . . 
Bureau Co. 
Mercer Co.. 

Montauk . 
Block . . 
Coking . . 
Cannel . . 
Cumberland 



Lignite 



Maryland. 

Arkansas. 
Colorado. 

Texas. 
Washington Ter. 



Pennsylvania. Petroleum 



Per Cent 

of 

Ash. 



6.13 
2.90 
15.02 
6.50 

10.70 
5.00 
5.60 
9.50 
2.75 

2.00 
14.80 
7.00 
5.20 
5.60 

5.50 

2.50 
5.66 
6.00 
13.88 

5.00 
9.25 
4.50 
4.50 
3.40 



Theoretical Value. 



In Heat 
Units. 



14,199 
13,535 
14,221 
13,143 
13,368 

13,155 
14,021 
14,265 
12,324 
14,391 

15,198 
13,360 
9,326 
13,025 
13,123 

12,659 
13,588 
14,146 
13,097 
12,226 

9,215 
13,562 
13,866 
12,962 
11,551 

20,746 



Pounds of 
Water 
Evap. 



14.70 
14.01 
14.72 
13.60 
13.84 

13.62 
14.51 
14.76 
12.75 
14.89 

16.76 
13.84 
9.65 
13.48 
13.58 

13.10 
14.38 
14.64 
13.56 
12.65 

9.54 
14.04 
14.35 
13.41 
11.96 

21.47 



The weight of solid coal varies from 80 lbs. to 100 lbs. per cubic foot. 



The Heating- Value of Coals. 



On page 851 are given the results (Sibley, Journal of Engineering) of some 
experiments made at Cornell University with a coarcalorimeter devised by 
Prof. R. C. Carpenter. It consists of two cylindrical chambers, in the inner 
one of which the sample of coal is burned in oxygen. The heated gases pass 
through a coiled copper tube about 10 feet long contained in the outer cham- 
ber. The coil is surrounded by water which expands, the expansion being 
measured in a finely graduated glass tube, thus giving the heat units in the 
coal. The calorimeter is calibrated by burning in it pure carbon. Follow- 
ing are the tables : 



FUEL. 



851 







pq 


© . 

=11 

a"°^ 


11801 
12036 
12149 
12294 
12307 
12423 
12903 
12934 
12943 
13051 
13254 
13324 
13723 




Ph 


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i 

pm 

5 

* 

V 


|| 

a?6 


10 10 10 10 

<M(NCS<N<Ni-<<M-H'#i-H10«0 


-3 5 

^5 


76.94 

71.68 

79.23 

84.46 

80.54 

75.2 

83.98 

85.7 

83.13 

86.68 

91.45 

87.96 

89.19 


fa 
9 

C 




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fa 
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*> 
a 

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Hi 






W.-Barre, Pa. 
Schuyl. Co., Pa. 
Scranton, Pa. 
Scranton, Pa. 
Scranton, Pa. 
L. V. Kegion . 
Scranton, Pa. 
Scranton, Pa. 
Scranton, Pa. 
Avondale, Pa. 
Scranton, Pa. 
Drifton, Pa. . 
Cross Creek, Pa 




co 
| 

3 






L. V. Buckwheat 
Jermyn . . 
"Woodward . . 
Cayuga . . . 
Mt. Pleasant . 
L. V. Pea . . 
Forty Foot . . 
Manville Shaft 
Continental . 
Avondale . . 
Oxford . . . 
Mammoth . . 
Buck Mountain 





a* 





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cq 








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852 



STEAM. 



Proximate A nalysis of Coal. 

(Power.) 



Designation of Coal. 



ANTHRACITE. 

Beaver Meadow, Penn 

Peach Mountain, Penn 

Lackawanna, Penn 

Lehigh, Penn 

Welsh, Wales 

SEMI- ANTHRACITE. 

Natural Coke, Virginia 

Cardiff, Wales 

Lycoming Creek, Penn 

Arkansas, No. 16 Geol. Survey .... 

SEMI-BITUMINOUS. 

Blosshurg, Penn 

Mexican 

Fort Smith, Arkansas 

Cliff, New South Wales, Australia . , 
Skagit River, State of Washington . , 

Cumberland, Maryland 

Cambria County, Penn , 

Mount Kembla, New South Wales, Aus 

Fire Creek, West Virginia , 

Arkansas, No. 12 Geol. Survey .... 

BITUMINOUS. 

Wilkeson, Pierce County, Washington , 

Cowlitz, Washington , 

New Elver, West Virginia , 

Pictou, Nova Scotia , 

Big Muddy, Illinois 

Bellingham Bay, Washington . . . , 

Midlothian, Virginia , 

Connellsville, Penn , 

Illinois, Average 

Carbon Hill, Washington , 

Clover Hill, Virginia 

Wellington, Vancouver Island, B.C. . . 

Franklin, Washington , 

Rocky Mountains 

Newcastle, England 

Mokihinui, Westport, New Zealand . . 
Brunner Mine, Greymouth, New Zealand 

Pittsburg, Penn 

Nanaimo, Vancouver Island, B.C. . . . 
Hocking Valley, Ohio ....... 

Pleasant Valley, Utah 

Kentucky 

Ellenslmrsr, Washington 

Olympic Mountains, Washington . . . 

Scotch, Scotland 

Roslyn, Washington 

Cook's Inlet, Alaska 

Kootznahoo Inlet, Admiralty I., Alaska 

Liverpool, England 

Calispel, Washington 

Carbonado, Washington 

Upper Yakima, Washington 

Methow, Washington 



P4^ 



1.5 

1.9 

2.12 

3.01 

1.2 

1.12 

1.25 

.67 

1.35 

1.34 
1.0 

1.07 
.85 

1.19 
.97 

2.46 

1.2 
.74 
.88 

1.33 
1.16 

.67 
2.57 
7.12 
3.98 
2.46 
1.26 
8.93 
2.16 
1.34 
2.15 
3.5 
7.55 
1.5 
3.96 
1.59 
1.7 
2.25 
6.95 
5.43 
2. 
2. 
5.1 
3.01 
3.1 
1.25 
3.74 

.89 
2.39 
1.8 
1.2 
2.5 



2.38 
2.96 
3.91 
3.28 
6.25 

12.44 
12.85 
13.84 
14.93 

14.78 

14.86 

17.2 

17.7 

18.8 

19.87 

20.52 

20.93 

22.42 

24.66 

25.88 

26.12 

26.64 

27.83 

29.5 

29.54 

29.86 

30.10 

30.14 

31.73 

32.21 

34.15 

34.27 

34.65 

34.7 

34.94 

35.68 

36. 

36.05 

36.15 

37.73 

37.89 

39.1 

39.15 

39.19 

39.7 

39.87 

37.02 

39.96 

41.18 

42.27 

42^47 

43.71 



0> O 

x-9 



88.94 
89.02 
87.74 
88.15 



75.08 
81.9 
71.53 
74.06 

73.11 

55.7 

73.05 

71.8 

71.66 

72.26 

69.37 

66.96 

75.5 

58.2 

66.75 

61.9 

70.66 

56.98 

54.64 

59.9 

53.01 

59.61 

45.93 

55.8 

56.83 

54.85 

54.23 

42.85 

59.3 

57.92 

56.62 

55. 

51.95 

51.3 

49.40 

56.01 

54.4 

47.01 

48.81 

52.65 

49.89 

45.15 

54.9 

42.92 

52.11 

52.21 

49.27 



FUEL. 



853 



Proximate Analysis of Coal — Continued. 







.Sg 


'C g 






Designation of Coal. 


P4^ 


II 


fa « 


» 
< 


CO 


Newcastle, King County, Washington . 


2.12 


46.7 


43.9 


7.15 


.13 


Black Diamond, King County,Washington 


3.11 


47.19 


45.11 


4.58 


.01 


Black Diamond, Mt. Diablo, California . 


14.69 


33.89 


46.84 


4.58 




LIGNITES. 












Otago (Kaitangata Cr.), New Zealand . 


19.61 


37.25 


39.41 


3.73 




Gilman, Washington 


4.8 


47.07 


37.19 


10.06 


.88 


Coos Bay (Newport Mine), Oregon . . 


15.45 


41.55 


34.95 


8.05 


2.53 


Alaska . . 


14.6 


44.85 


31.2 


9.35 


1.15 


Huron, Fresno County, California . . 


11.7 


51.73 


19.63 


16.94 


2.73 


lone, Amador County, California . . . 


42.58 34.88 


17.42 


5.12 


Trace. 



Space Required to Stow a Ton (2240 ll»s.) of Various 
Kind's of Coal. 

ANTHRACITE. 

Welsh, Wales 39 cubic feet. 

Peach Mountain, Penn 41.6 " " 

Beaver Meadow, Penn. 40.2 " " 

Lehigh, Penn 40.5 " " 

Lackawanna, Penn 45.8 " " 

SEMI-ANTHRACITE. 

Cardiff, Wales 38.3 cubic feet. 

Natural Coke, Virginia 50.2 " " 

SEMI-BITUMINOUS. 

Cumberland, Virginia 41.7 cubic feet. 

Blossburgh, Penn 42.2 " " 

Mt. Kembla, Australia 37.7 " " 

Mexican 36.7 " " 

BITUMINOUS. 

New River, Virginia 46 cubic feet. 

Wellington, Vancouver Island, B.C 41.8 " " 

Midlothian, Virginia 41.4 " " 

Newcastle, England 44 " " 

Pictou, Nova Scotia 45 " " 

Scotch Splint, Fordel 40.7 •' " 

Pleasant Valley, Utah 42.3 " " 

Sydney, N. S. W., Australia 47.2 " " 

Takasima, Japan 46.4 " " 

Pittsburgh. Penn 47.8 " " 

Liverpool, England 46.7 " " 

Scotch, Dalkeith 43.8 " " 

Carbon Hill, Washington 36.9 " " 

Clover Hill, Virginia 49.2 " " 

Bocky Mountain 41.2 " " 

LIGNITE. 

Alaska 41.8 cubic feet. 

WOOD. 

Dry pine wood 107 cubic feet. 

Coke. — Coke from ovens, preferred to gas coke as fuel, weighs with 
few exceptions about 40 lbs. per bushel. Light coke will weigh 33 to 38 lbs. 
Heavy coke, 42 to 50 lbs. 

Analysis of Coke. 
(From report of John B. Procter, Kentucky Geological Survey.) 



Wliere Made. 


Fixed 
Carbon 


Ash. 


Sul- 
phur. 


Connellsville, Pa. (Average of 3 samples) . . . 
Chattanocga, Tenn. " "4 " ... 
Birmingham, Ala. " "4 " ... 
Pocahontas, Va. " " 3 " ... 
New Biver, W. Va. " "8 " ... 
Big Stone Gap, Ky. " " 7 " ... 


88.96 
80.51 
87.29 
92.53 
92.38 
93.23 


9.74 
16.34 
10.54 

5.74 

7.21 
5.69 


0.810 
1.595 
1.195 
0.597 
562 
0.749 



854 



STEAM. 



Wood aw fuel. 

Green wood contains from 30 to 50 per cent of moisture. After about a 
year in open air the moisture is 20 to 25 per cent. 

The woods of various trees are nearly identical in chemical composition, 
which is practically as follows, showing the composition of perfectly dry 
wood, and of ordinary firewood holding hygroscopic moisture : 

Desiccated Wood. Ordinary Firewood. 

. . . . 50 per cent . . . 37.5 per cent 

. ... 6 per cent ... 4.5 per cent 

.... 41 per cent . . . 30.75 per cent 

.... 1 per cent . . . 0.75 per cent 

. . . . 2 per cent ... 1.5 per cent 

100 per cent 75.0 per cent 

Hygrometric water 25.0 per cent 

100.0 
Some of the pines and others of the coniferous family contain hydrocar- 
bons (turpentine). Ash varies in American woods from .03 per cent to 1.20 
per cent. 

In steam boiler tests wood is assumed as 0.4 the value of the same weight of 
coal. 

The fuel value of the same weights of wood of all kinds is practically the 
same ; and it is important that the Avood be dry. 



Carbon . 
Hydrogen 
Oxygen 
Nitrogen 
Ash . . 



Weight o 


f Wood per Cord. 




Weighs per 
Cord, Lbs. 


Equal in value to Coal, 
in Lbs. 


Average pine 

Poplar, chestnut, elm 

Beech, red and black oak .... 


2000 
2350 
3250 
3850 
4500 


800 to 925 
940 to 1050 
1300 to 1450 
1540 to 1715 


Hickory and hard maple .... 


1800 to 2000 



A cord of wood = 4x4x8 
wood, and 44 per cent spaces. 



128 cubic feet. About 56 per cent is solid 



(Liquid Fuels. 

Petroleum is a hydrocarbon liquid which is found in abundance in Amer- 
ica and Europe. According to the analysis of M. Sainte-Claire Deville, the 
composition of 15 petroleums from different sources was found to be practi- 
cally the same. The average specific gravity was .870. The extreme and the 
average elementary compositions were as follows : 



Chemical Composition of Petroleum. 



Carbon 82.0 to 87.1 per cent. 

Hydrogen 11.2 to 14.8 per cent. 

Oxygen 0.5 to 5.7 per cent. 



Average, 84.7 per cent. 
Average, 13.1 per cent. 
Average, 2.2 per cent. 



100.0 
The total heating and evaporative powers of one pound of petroleum hav- 
ing this average composition are as follows : 

Total heating power = 145 [84.7 + (4.28 x 13.1)] = 20411 units. 
Evaporative power : evaporating at 212°, water supplied at 62° = 18.29 lbs. 
Evaporative power : evaporating at 212°, water supplied at 212° = 21.13 lbs. 
Petroleum oils are obtained in great variety by distillation from petro- 
leum. They are compounds of carbon and hydrogen, ranging from C 10 H 24 
to C 32 H G1 ; or, in weight ; 



FUEL. 



855 



Chemical Composition of Petroleum Oils 

71.42 Carbon 



From 



28.58 Hydrogen 



to 



73.77 Carbon . 
26.23 Hydrogen 



100.00 



100.00 



Mean. 
72.60 
27.40 

100.00 



The specific gravity ranges from .62S to .792. The boiling point ranges 
from 86° to 495° F. The total heating power ranges from 2808/ to 26975 units 
of heat ; equivalent to the evaporation, at 212°, of from 25.17 to 24.17 lbs. 
of water supplied at 62°, or from 29.08 lbs. to 27.92 lbs. of water supplied 
at 212°. 

[Furnaces for the combustion of oil fuel need not be as large as when 
burning coal, as the latter, being solid matter, requires more time for de- 
composition, and the elimination of the products and supporters of com- 
bustion. Coal fuel requires a large fire chamber and the means for the 
introduction of air beneath the grate-bars to aid combustion. Compared 
with oil, the combustion of coal is tardy, and requires some aid by way of 
a strong draft. Oil having no ash or refuse, when properly burned, requires 
much less space for combustion, for the reason that, being a liquid, and the 
compound of gases that are highly inflammable when united in proper pro- 
portions, it gives off heat with the utmost rapidity, and at the point of igni- 
tion is all ready for consumption. 

Gaseous Fuels. — Mr. Emerson McMillin (Am. Gas. Lt. Asso., 1887) 
made an exhaustive investigation of the subject of fuel gas ; he states that 
the relative values of these gases, considering that of natural gas as of unit 
value, are : 



Natural gas . 
Coal gas . . . 
Water gas . . 
Producer gas . 



By Weight. 



1000 
949 
292 



By Yoiume. 



1000 
666 
292 
130 



The water gas rated in the above table is the gas obtained in the decom- 
position of steam by incandescent carbon, and does not attempt to fix the 
calorific value of illuminating water gas, which may be carbureted so as to 
exceed, when compared by volume, the value of coal gas. 



Composition of Gases. 



Hydrogen . . . 
Marsh gas . . 
Carbonic oxide 
defiant gas . . 
Carbonic acid . 
Nitrogen . . . 
Oxygen . . . 
Water vapor 
Sulphydric acid 



Volume. 



Natural 
Gas. 



2.18 
92.60 
0.50 
0.31 
0.26 
3.61 
0.34 
0.00 
0.20 



100.00 



Coal 

Gas. 



46.00 
40.00 
6.00 
4.00 
0.50 
1.50 
0.50 
1.50 



100.00 



Water 

Gas. 



45.00 
2.00 

45.00 
0.00 
4.00 
2.00 
0.50 
1.50 



100.00 



Producer 

Gas. 



6.00 
3.00 

23.50 
0.00 
1.50 

65.00 
0.00 
1.00 



856 



STEAM. 



mechanical Stoking*. 

In boiler installations that can be conveniently handled by one man it is 
doubtful if Ave can improve on the best hand firing ; but where good firemen 
are scarce, or the installation is of considerable size, there can be no doubt 
that the use of some form of mechanical stoker will result in economy, and 
especially in the prevention of large quantities of smoke, as the combustion 
is gradual and more nearly perfect. 

The types may perhaps be limited to three : the straight feed, as the Mur- 
phy, Koney, Wilkinson, and Brightman ; the under-feed of which the 
"American" is a good representative; and the chain stoker, by Coxe and 
the B. & W. Co. 

Mechanical draught is generally used with the two last-mentioned types, 
and sometimes with the first. 

Mr. Eckley B. Coxe developed the chain stoker in the most scientific man- 
ner for the use of the cheap coals of the anthracite region. 

The advantages and disadvantages of mechanical stokers are stated 
by Mr. J. M. Whitham (Trans. A.S.M.E., vol. xvii. p. 558) to be as follows : 
Advantages. 1. Adaptability to the burning of tbe cheapest grades of fuel. 
2. A 40 per cent labor saving in plants of 500 or more h. p., when provided with 
coal-handling machinery. 3. Economy in combustion, even under forced 
firing, with proper management. 4. Constancy and uniformity of furnace 
conditions, the fires being clean at all times, and responding to sudden de- 
mands made for power. This should result in prolonged life of boilers. 
5. Smokelessness. Disadvantages. 1. High first cost, varying from $25 to 
$ 40 per square foot of grate area. 2. High cost of repairs per year, which, 
with some stokers, is as much as $5 per square foot. 3. The dependence of 
the power-plant upon the stoker engine's working. 4. Steam cost of run- 
ning the stoker engine, which is from | to § of 1 per cent of the steam generated. 
This is about $50 a year on a 10-hour basis for 1000 h. p., where fuel is $2 per 
ton. 5. Cost of steam used for a steam blast, or for driving a fan blast, 
whenever either is used. This, for a steam blast, is from 5 per cent to 11 
per cent of the steam generated by the boilers, and from 3 per cent to 5 per 
cent for a fan blast. This amounts to about $1000 per year for a steam blast, 
and $500 a year in fuel for a fan blast, for a 1000 h. p. plant on a 10-hour 
basis, when fuel is $2 per ton. 6. Skill required to operate the stoker. 
Careless management causes either loss of fuel in the ash, or loss due to 
poor combustion when the coal is too soon burned out on the grate, thus per- 
mitting cold air to freely pass through the ash. 7. The stoker is a machine 
subject to a severe service, and, like any other machine, wears out and 
requires constant attention. 



WATER. 

Weight of Water per Cuhic Toot, from 32° to 212° F., and heat- 
units per pound, reckoned above 32° F. (Wm. Kent, Trans. A. S. M. E., 
vi. 90.) 





flO 


w 




is 


CO 




■2.S 


CO 




J.2 


oi 




'-<£ 


J* 


rt 


•^^3 


.1- 


j 


"l* 


."£ 


■ 


"-\a 


S 


-fa 


5 ° ■ 


£ 


°/- 


j-3 


2 


S/ 5 


2 ° 4* 


p 


2 fa 


hOj 


■3 


fj-ti 


bJD '-* z 


z 


&£ be 


'tii'- c 




^£bi 


bfi "- O 




a I ti 


bD'-< C 




£ v 


-? -' ~ 


c« 


3a« 


.,-. a, - 


c3 


255 


.-. -J ~ 


a 


!£•§ 


■« ® z 


cS 


S"-i 


5 PV-H 


0J 


S-Sts 


® erf5 


a> 


s+m 


® p,<S 


CD 


« ft-+H 


CD 


H 


l> 


W 


H 


£ 


w 


H 


£ 


w 


H 


^ 


w 


32 


62.42 


0. 


41 


62.42 


9. 


50 


62.41 


18. 


59 


62.38 


27.01 


33 


62.42 


l. 


42 


62 42 


10. 


51 


62.41 


19. 


60 


62.37 


28.01 


34 


62.42 


2. 


43 


62.42 


11. 


52 


62.40 


20. 


61 


62.37 


29.01 


35 


62.42 


3. 


44 


62.42 


12. 


53 


62.40 


21.01 


62 


62.36 


30.01 


36 


62.42 


4. 


45 


62.42 


13. 


54 


62.40 


22.01 


63 


62.36 


31.01 


37 


62.42 


5. 


46 


62.42 


14. 


55 


62.39 


23,01 


64 


62.35 


32.01 


38 


62.42 


6. 


47 


62.42 


15. 


56 


62.39 


24.01 


65 


62.34 


33.01 


39 


62.42 


7. 


48 


64.41 


16. 


57 


62.39 


25.01 


66 


62.34 


34.02 


40 


62.42 


8. 


49 


62.41 


17. 


58 


62.38 


26.01 


67 


62.33 


35.02 



WATER. 



857 



Weight of Water — Continued. 





j§ 2 


03 




i.s 


oi 




J .2 


03 




J§2 


05 




r-,fi 




& to 

oT • 


Hja 




i to 
2 a? • 


r^-O 




& to 


K,Q 




Jto 




5 




2 


^-3 


p 


«3 


3 


a&b 


bDu O 


^i 


^£ M 


bC^ 5 


.ji 


^£ M 


bC^ O 


j± 


a? sd 


btou O 




fl © 

$-3 


|fa 


© 


2 23 


"S ©P 


© 




•r- aj O 

^ Ato 


© 


2 =,£ 


^Ato 


e3 

© 


H 


w 


H 


W 


H 


? 


w 


H 


w 


68 


62.33 


36.02 


105 


61.96 


73.10 


141 


61.36 


109.25 


177 


60.62 


145.52 


69 


62.32 


37.02 


106 


61.95 


74.10 


142 


61.34 


110.26 


178 


60.59 


146.52 


70 


62.31 


38.02 


107 


61.93 


75.10 


143 


61.32 


111.26 


179 


60.57 


147.53 


71 


62.31 


39.02 


108 


61.92 


76.10 


144 


61.30 


112.27 


180 


60.55 


148.54 


72 


62.30 


40.02 


109 


61.91 


77.11 


145 


61.28 


113.28 


181 


60.53 


149.55 


73 


62.29 


41.02 


110 


61.89 


78.11 


146 


61.26 


114.28 


182 


60.50 


150.56 


74 


62.28 


42.03 


111 


61.88 


79.11 


147 


61.24 


115.29 


183 


60.48 


151.57 


75 


62.28 


43.03 


112 


61.86 


80.12 


148 


61.22 


116.29 


184 


60.46 


152.58 


76 


62.27 


44.03 


113 


61.85 


81.12 


149 


61.20 


117.30 


185 


60.44 


153.59 


77 


62.26 


45.03 


114 


61.83 


82.13 


150 


61.18 


118.31 


186 


60.41 


154.60 


78 


62.25 


46.03 


115 


61.82 


83.13 


151 


61.16 


119.31 


187 


60.39 


155.61 


79 


62.24 


47.03 


116 


61.80 


84.13 


152 


61.14 


120.32 


188 


60.37 


156.62 


80 


62.23 


48.04 


117 


61.78 


85.14 


153 


61.12 


121.33 


189 


60.34 


157.63 


81 


62.22 


49.04 


118 


61.77 


86.14 


154 


61.10 


122.33 


190 


60.32 


158.64 


82 


62.21 


50.04 


119 


61.75 


87.15 


155 


61.08 


123.34 


191 


60.29 


159.65 


83 


62.20 


51.04 


120 


61.74 


88.15 


156 


61.06 


124.35 


192 


60.27 


160.67 


84 


62.19 


52.04 


121 


61.72 


89.15 


157 


61.04 


125.35 


193 


60.25 


161.68 


85 


62.18 


53.05 


122 


61.70 


90.16 


158 


61.02 


126.36 


194 


60.22 


162.69 


86 


62.17 


54.05 


123 


61.68 


91.16 


159 


61.00 


127.37 


195 


60.20 


163.70 


87 


62.16 


55.05 


124 


61.67 


92.17 


160 


60.98 


128.37 


196 


60.17 


164.71 


88 


62.15 


56.05 


125 


61.65 


93.17 


161 


60.96 


129.38 


197 


60.15 


165.72 


89 


62.14 


57.05 


126 


61.63 


94.17 


162 


60.94 


130.39 


198 


60.12 


166.73 


90 


62.13 


58.06 


127 


61.61 


95.18 


163 


60.92 


131.40 


199 


60.10 


167.74 


91 


62.12 


59.06 


128 


61.60 


96.18 


164 


60.90 


132.41 


200 


60.07 


168.75 


92 


62.11 


60.06 


129 


61.58 


97.19 


165 


60.87 


133.41 


201 


60.05 


169.77 


93 


62.10 


61.06 


130 


61.56 


98.19 


166 


60.85 


134.42 


202 


60.02 


170.78 


94 


62.09 


62.06 


131 


61.54 


99.20 


167 


60.83 


135.43 


203 


60.00 


171.79 


95 


62.08 


63.07 


132 


61.52 


100.20 


168 


60.81 


136.44 


204 


59.97 


172.80 


96 


62.07 


64.07 


133 


61.51 


101.21 


169 


60.79 


137.45 


205 


59.95 


173.81 


97 


62.06 


65.07 


134 


61.49 


102.21 


170 


60.77 


138.45 


206 


59.92 


174.83 


98 


62.05 


66.07 


135 


61.47 


103.22 


171 


60.75 


139.46 


207 


59.89 


175.84 


99 


62.03 


67.08 


136 


61.45 


104.22 


172 


60.73 


140.47 


208 


59.87 


176.85 


100 


62.02 


68.08 


137 


61.43 


105.23 


173 


60.70 


141.48 


209 


59.84 


177.86 


101 


62.01 


69.08 


188 


61.41 


106.23 


174 


60.68 


142.49 


210 


59.82 


178.87 


102 


62.00 


70.09 


139 


61.39 


107 24 


175 


60.66 


143.50 


211 


59.79 


179.89 


103 


61.99 


71.09 


140 


61.37 


108.25 


176 


60.64 


144.51 


212 


59.76 


180.90 


104 


61.97 


72.09 




1 















Weight of Water at Temperatures Above 313° *\ 

(Dr. R. H. Thurston, " Engine and Boiler Trials," p. 548.) 





















o 


u -^ 


gilt, 
nds 
Cubi 
t. 


<k ■ 

© 0> 




© © . 


13 «? 

bJ0flO+^ 






© oT^ 


IfL- 


s jl g> 


® ^ u 9, 


9 43 <*> 
© O 

H 


© 3 u o 






flP W) 


© 2 H O 




'3 ^ ^ © 


© Q 




►>. o © © 


©^Q 
H 


> o © ,© 


©~^0 


b* o ©o 




t*. o © r ° 

> AAto 


212 


59.71 280 


57.90 


350 


55.52 


420 


52.86 


490 


50.03 


220 


59.64 


290 


57.59 


360 


55.16 


430 


52.47 


500 


49.61 


230 


59.37 


300 


57.26 


370 


54.79 


440 


52.07 


510 


49.20 


240 


59.10 


310 


56.93 


380 


54.41 


450 


51.66 


520 


48.78 


250 


58.81 


320 


56.58 


390 


54.03 


460 


51.26 


530 


48.36 


260 


58.52 


330 


56.24 


400 


53.64 


470 


50.85 


540 


47.94 


270 


58.21 


340 


55.88 


410 


53.26 


480 


50.44 


550 


47.52 



858 



STEAM. 
Expansion of Water. 



(Kopp : corrected by Porter.) 



Cent. 


Fahr. 


Volume. 


Cent. 


Fahr. 


Volume. 


Cent. 


Fahr. 


Volume. 


4° 


39.2° 


1.00000 


35° 


95° 


1.00586 


70° 


158° 


1.02241 


5 


41 


1.00001 


40 


104 


1.00767 


75 


167 


1.02548 


10 


50 


1.00025 


45 


113 


1.00967 


80 


176 


1.02872 


15 


59 


1.00083 


50 


122 


1.01186 


85 


185 


1.03213 


20 


68 


1.00171 


55 


131 


1.01423 


90 


194 


1.03570 


25 


77 


1.00286 


60 


140 


1.01678 


95 


203 


1.03943 


30 


86 


1.00425 


65 


149 


1.01951 


100 


212 


1.04332 



Water for Boiler JTeed. 

(Hunt and Clapp, A. I. M. E., 1888.) 

Water containing more than 5 parts per 100,000 of free sulphuric or nitric 
acid is liable to cause serious corrosion, not only of the metal of the boiler 
itself, but of the pipes, cylinders, pistons, and valves with which the steam 
comes in contact. 

The total residue in water used for making steam causes the interior lin- 
ings of boilers to become coated, and often produces a dangerous hard scale, 
which prevents the cooling action of the water from protecting the metal 
against burning. 

Lime and magnesia bicarbonates in water lose their excess of carbonic 
acid on boiling, and often, especially when the water contains sulphuric 
acid, produce, with the other solid residues constantly being formed by the 
evaporation, a very hard and insoluble scale. A larger amount than 100 
parts per 100,000 of total solid residue will ordinarily cause troublesome 
scale, and should condemn the water for use in steam boilers, unless a bet- 
ter supply can be obtained. 

The following is a tabulated form of the causes of trouble with water for 
steam purposes, and the proposed remedies, given by Prof. L. M. Norton. 

CAUSES OF INCRUSTATION. 

1. Deposition of suspended matter. 

2. Deposition of deposed salts from concentration. 

3. Deposition of carbonates of lime and magnesia by boiling off carbonic 
acid, which holds them in solution. 

4. Deposition of sulphates of lime, because sulphate of iime is but slightly 
soluble in cold water, less soluble in hot water, insoluble above 270° F. 

5 Deposition of magnesia, because magnesium salts decompose at high 
temperature. 
6. Deposition of lime soap, iron soap, etc., formed by saponification ?f 



MEANS FOR PREVENTING. INCRUSTATION. 

1. Filtration. 

2. Blowing off. 

3. Use of internal collecting apparatus or devices for directing the circu- 
lation. 

4. Heating feed-water, 



WATER. 



859 



5. Chemical or other treatment of water in boiler. 

6. Introduction of zinc into boiler. 

7. Chemical treatment of water outside of boiler. 

TABULAR VIEW. 



Trouble. 
Incrustation. 



Troublesome Substance. 
Sediment, mud, clay, etc. 
Readily soluble salts. 

Bicarbonates of lime, magnesia, 
iron. 



Sulphate of lime. " 

Chloride and sulphate of magne- ) Corrosion 



Carbonate of soda in large 
amounts. 

Acid (in mine waters). 

Dissolved carbonic acid and oxy- 
gen. 



Grease (from condensed water). 

Organic matter (sewage). 
Organic matter. 



Priming. 

Corrosion. 



Priming. 
Corrosion. 



Remedy or Palliation. 

Filtration, Blowing off. 

Blowing off. 

( Heating feed. Addition of 
\ caustic soda, lime, or 
^ magnesia, etc. 

f Addition of carb. soda, 
\ barium chloride, etc. 

f Addition of carbonate of 
( soda, etc. 

f Addition of barium chlo- 
( ride, etc. 

Alkali. 

{Heating feed. Addition 
of caustic soda, slacked 
lime, etc. 

f Slacked lime and filtering, 
<{ Carbonate of soda, 
t. Substitute mineral oil. 

( Precipitate with alum or 
\ ferric chloride and filter. 

Ditto. 



Solubilities of Scale-making- Material*. 



(" Boiler Incrustation," F. J. Rowan.) 

The salts of lime and magnesia are the most common of the impurities 
found in water. Carbonate of lime is held in solution in fresh water by an 
excess of carbonic acid. By heating the water the excess of carbonic acid 
is driven off and the greater part of the carbonate precipitated. At ordi- 
nary temperatures carbonate of lime is soluble in from 16,000 to 24,000 times 
its volume of water ; at 212° F. it is but slightly soluble, and at 290° F. (43 
lbs. pressure) it is insoluble. 

The solubility of sulphate of lime is also affected by the temperature ; 
according to Regnault, its greatest solubility is at 95° F., where it dissolves 
in 393 times its weight of water ; at 212- F. it is only soluble in 460 times ita 
weight of water, and according to M. Coute, it is insoluble at 290° F. 

Carbonate of magnesia usnally exists in much smaller quantity than the 
salts of lime. The effect of temperature on its solubility is similar to that 
of carbonate of lime. 

Prof. R. H. Thurston, in his " Manual of Steam Boilers," p. 261, states 
that: 

The temperatures at which calcareous matters are precipitated are : 

Carbonate of lime between 176° and 248° F. 

Sulphate of lime between 284° and 424° F. 

Chloride of magnesium between 212° and 257° F. 

Chloride of sodium between 324° and 364° F. 



860 STEAM. 



" Incrustation and sediment," Prof. Thurston says, " are deposited in 
boilers, the one by the precipitation of mineral or other salts previously 
held in solution in the feed-water, the other by the deposition of mineral 
insoluble matters, usually earths, carried into it in suspension or me- 
chanical admixture. Occasionally also vegetable matter of a glutinous 
nature is held in solution in the feed-water, and, precipitated by heat or 
concentration, covers the heating-surfaces with a coating almost impermea- 
ble to heat, and hence liable to cause an over-heating that may be very dan- 
gerous to the structure. A powdery mineral deposit sometimes met with is 
equally dangerous, and for the same reason. The animal and vegetable oils 
and greases carried over from the condenser or feed-water heater are also 
very likely to cause trouble. Only mineral oils should be permitted to be 
thus introduced, and that in minimum quantity. Both the efficiency and 
the safety of the boiler are endangered by any of these deposits. 

"The only positive and certain remedy for incrustation and sediment 
once deposited is periodical removal by mechanical means, at sufficiently 
frequent intervals to insure against injury by too great accumulation. Be- 
tween times, some good may be done by special expedients suited to the 
individual case. No one process and no one antidote will suffice for all 



" Where carbonate of lime exists, sal-ammoniac may be used as a pre- 
ventive of incrustation, a double decomposition occurring, resulting in the 
production of ammonium carbonate and calcium chloride — both of which 
are soluble, and the first of which is volatile. The bicarbonate may be in 
part precipitated before use by heating to the boiling-point, and thus break- 
ing up the salt and precipitating the insoluble carbonate. Solutions of 
caustic lime and metallic zinc act in the same manner. Waters containing 
tannic acid and the acid juices of oak, sumach, logwood, hemlock, and other 
woods, are sometimes employed, but are apt to injure the iron of the boiler, 
as may acetic or other acid contained in the various saccharine matters 
often introduced into the boiler to prevent scale, and which also make the 
lime-sulphate scale more troublesome than when clean. Organic matters 
should never be used. 

" The sulphate scale is sometimes attacked by the carbonate of soda, the 
products being a soluble sodium sulphate and a pulverulent insoluble cal- 
cium carbonate, which settles to the bottom like other sediments and is 
easily washed off the heating-surfaces. Barium chloride acts similarly, 
producing barium sulphate and calcium chloride. All the alkalies are used 
at times to reduce incrustations of calcium sulphate, as is pure crude petro- 
leum, the tannate of soda, and other chemicals. 

" The effect of incrustation and of deposits of various kinds is to enor- 
mously reduce the conducting power of heating-surfaces ; so much so, that 
the power, as well as the economic efficiency of a boiler, may become very 
greatly reduced below that for which it is rated, and the supply of steam 
furnished by it may become Avholly inadequate to the requirements of the 
case. 

" It is estimated that a sixteenth of an inch thickness of hard ' scale' on 
the heating-surface of a boiler will cause a waste of nearly one-eighth its 
efficiency, and the waste increases as the square of its thickness. The boil- 
ers of steam vessels are peculiarly liable to injury from this cause where 
using salt water, and the introduction of the surface-condenser has been 
thus brought about as a remedy. Land boilers are subject to incrustation 
by the carbonate and other salts of lime, and by the deposit of sand or mud 
mechanically suspended in the feed-water." 

Kerosene oil ("Boiler Incrustation," Rowan) has been used to advantage in 
removing and preventing incrustation. From extended experiments made 
on a 100 h. p. water tube boiler, fed with water containing 6.5 grains of 
solid matter per gallon, it was found that one quart kerosene oil per day 
was sufficient to keep the boiler entirely free from scale. Prior to the in- 
troduction of the kerosene oil, the water had a corrosive action upon some 
of the fittings attached to the boiler ; but after the oil had been used for a 
few months it was found that the corrosive action had ceased. 

It should be stated, however, that objection has been made to the intro- 
duction of kerosene oil into a boiler for the purpose of preventing incrusta- 



WATER. 861 



tion, on account of the possibility of some of the oil passing with the steam 
into the cylinder of the engine, and neutralizing the effect of the lubricant 
in the cylinder. 

"When oil is used to remove scale from steam-boilers, too much care can- 
not be exercised to make sure that it is free from grease or animal oil. 
Nothing but pure mineral oil should be used. Crude petroleum is one 
thing ; black oil, which may mean almost anything, is very likely to be 
something quite different. 

The action of grease in a boiler is peculiar. It does not dissolve in the 
water, nor does it decompose, neither does it remain on top of the water ; 
but it seems to form itself into "slugs," which at first seem to be slightly 
lighter than the water, so that the circulation of the water carries them 
about at will. After a short season of boiling, these " slugs," or suspended 
drops, acquire a certain degree of " stickiness," so that when they come in 
contact with shell and flues of the boiler, they begin to adhere thereto. 
Then under the action of heat they begin the process of " varnishing " the 
interior of the boiler. The thinnest possible coating of this varnish is suf- 
ficient to bring about over-heating of the plates. 

The time when damage is most likely to occur is after the fires are banked, 
for then, the formation of steam being checked, the circulation of water 
stops, and the grease thus has an opportunity to settle on the bottom of the 
boiler and prevent contact of the water with the fire-sheets. Under these 
circumstances, a very low degree of heat in the furnace is sufficient to over- 
heat the plates to such an extent that bulging is sure to occur. 

Zinc as a Scale Preventive. — Dr. Corbigny gives the following hypoth- 
esis : he says that " the two metals, iron and zinc, surrounded by water at a 
high temperature, form a voltaic pile with a single liquid, which slowly 
decomposes the water. The liberated oxygen combines with the most oxy- 
dizable metal, the zinc, and its hydrogen equivalent is disengaged at the 
surface of the iron. There is thus generated over the whole extent of the 
iron influenced a very feeble but continuous current of hydrogen, and 
the bubbles of this gas isolate at each instant the metallic surface from the 
scale-forming substance. If there is but little of the latter, it is penetrated 
by these bubbles and reduced to mud ; if there is more, coherent scale is 
produced, which, being kept off by the intervening stratum of hydrogen, 
takes the form of the iron surface without adhering to it." 

Zinc, in the shape of blocks, slabs, or as shavings inclosed in a perforated 
vessel, should be suspended throughout the water space of a boiler, care 
being used in getting perfect metallic contact between the zinc and the 
boiler. It should not be suspended directly over the furnace, as the oxide 
might fall upon the surface and be the cause of the plate being over-heated. 
The quantity placed in a boiler should vary with the hardness of the water, 
and the amount used, and should be measured by the surface presented. 
Generally one square inch of surface for every 50 lbs. water in the boiler is 
sufficient. The British Admiralty recommends the renewing of the blocks 
whenever the decay of the zinc has penetrated the slab to a depth of J inch 
below the surface. 

Purification of JTeed- Water by Boiling-. 

Sulphates can be largely removed from feed-water by heating it to the tem- 
perature due to boiler pressure in a feed-water heater, or " live steam puri- 
fier " before introduction to boiler. This precipitates those salts in the heater 
and the water can then if necessary be pumped through a filter into the boiler. 
The feed-water ij first heated as hot as possible in the ordinary exhaust 
feed-water heater in which the carbonates are precipitated, and then run 
through the purifier, which is most generally a receptacle containing a 
number of shallow pans, that can be removed' for cleaning, over which the 
feed- water is allowed to flow from one to the other in a thin sheet. Live 
steam at boiler-pressure is introduced into the purifier, heating the water 
to a temperature high enough to precipitate the salts which form scale on 
the pans. This method of treating feed-water is said to largely increase the 
efficiency of a boiler plant by the almost complete avoidance of scale. 
Purification of feed-water by filtration before introduction to the system is 
often practised with good results. 



862 



STEAM. 



Table of Water Analyses. 

Grains per U. S. Gallon of 231 Cubic Inches. 



Where From. 



Buffalo, N. Y., Lake Erie .... 
Pittsburgh, Allegheny River . . 
Pittsburgh, Monongahela River . 
Pittsburgh, Pa., artesian well . . 
Milwaukee, Wisconsin River . . . 

Galveston, Texas, 1 

Galveston, Texas, 2 

Columbus, Ohio 

Washington, D. C, city supply . . 
Baltimore, Md., city supply . . . 
Sioux City, la., city supply .... 

Los Angeles, Cal., 1 

Los Angeles, Cal., 2 

Bay City, Michigan, Bay 

Bay City, Michigan, River .... 

Cincinnati, Ohio River 

Watertown, Conn 

Fort Wayne, Ind 

Wilmington, Del 

Wichita, Kansas 

Springfield, 111., 1 

Springfield, 111., 2 

Hillsboro, 111 

Pueblo, Colo 

Long Island City, L. I 

Mississippi River, above Missouri 

River 

Mississippi River, below mouth of 

Missouri River 

Mississippi River at St. Louis, W. W. 
Hudson River, above Poughkeepsie 

N. Y 

Croton River, above Croton Dam, 

N. Y 

Croton River water from service 

pipes in New York City 

Schuylkill River, above Philadelphia 

Pa 













03 




















cti 










a 


<D 




y 


u 


o 








<v 


>fi 


A 




<d 


S 


c3 

o 


ft 
2 




A 


S 


c3 


CO 


CO 




© 




cS 


v ""' 


co 


a 


<a 








08 


s 


ID 




& 


bO 


be 




T3 






a 


be 




c3 


O 


s 




o 


O 




-d 


Td 


6 


T3 


OS 


eS 


3 


a 


X 

O 


o 


01 

s 


2 


^3 


o 


cS 


3 


h3 


co 


H 


K* 


5.66 


3.32 


0.58 




0.18 


0.37 


3.78 


0.58 


0.37 


1.50 


1.06 


5.12 


0.64 


0.78 


3.20 


23.45 


5.71 


18.41 


1.04 


0.82 


6.23 


4.67 


1.76 


20.14 


6.50 


13.68 


13.52 


326.64 


Trace 


Trace 


21.79 


29.15 


398.99 




4.00 


20.76 


11.74 


7.02 


0.58 


6.50 


2.87 


3.27 


Trace 


0.36 


2.10 


2.77 


0.65 


Trace 


0.10 


3.80 


19.76 


1.24 


1.17 


1.03 


4.40 


10.12 


5.84 


3.51 


2.63 


4.10 


3.72 


12.59 




0.76 


6.00 


8.47 


10.36 


20.48 


1.15 


8.74 


4.84 


33.66 


126.78 


3.00 


10.92 


3.88 


0.78 


1.79 




Trace 


1.47 


4.51 


1.76 


Trace 


1.78 


8.78 


6.22 


3.51 


1.59 


10.98 


10.04 


6.02 


4.29 


8.48 


6.17 


14.14 


25.91 


24.34 




2.00 


12.99 


7.40 


1.97 


2.19 


8.62 


5.47 


4.31 


1.56 


4.28 


5.83 


14.56 


2.97 


2.39 


1.63 


Trace 


4.32 


16.15 


1.20 


1.97 


5.12 


4.0 


28.0 


16.0 




1.0 


8.24 


1.02 


0.50 




5.25 


10.64 


7.41 


1.36 


1.22 


15.86 


9.64 


6.94 


1.54 


1.57 


9.85 


1.06 




.11 


10.76 


.77 


4.57 


.16 


.40 


1.92 


.67 


2.36 






1.36 




2.16 


.29 


.49 


1.30 





9.74 

6.60 

10.80 

49.43 

39.30 

353.84 

453.93 

46.60 

8.60 

7.30 

27.60 

26.20 

23.07 

49.20 

179.20 

6.73 

9.52 

31.08 

35.00 

66.39 

33.17 

21.45 

21.55 

28.76 

39.0 

15.01 

36.49 
29.54 

12.70 

7.72 

3.72 

4.24 



pumps. 863 

PUMPS. 

Feed-Pumps. 

These should be at least double the capacity found by calculation from 
the amount of water required for the engines, to allow for blowing off, leak- 
age, slip in the pumps themselves, etc., and to enable the pump to keep 
down steam in case of sudden stoppage of the engines when the fires hap- 
pen to be brisk, and in fact should be large enough to supply the boilers 
when run at their full capacity. In addition, for all important plants, there 
should be either a duplicate feed-pump or an injector to act as stand-by in 
case of accident. The speed of the plunger or piston may be 50 feet per 
minute and should never exceed 100 feet per minute, else undue wear and 
tear of the valves results, and the efficiency is reduced. If the pump be re- 
quired to stand idle without continually working, the plunger or piston and 
rod should be of brass. 



If 



D = diameter of barrel in inches, 

S = stroke in inches, 

n = number of useful strokes per minute, 

w = cubic feet of water pumped per hour, 

JF=: lbs. of water pumped per hour ; 

w = 1.7 £*Sn. 

Z> 2 Sn 



W = 

Vr 36.6 

If Sn = 50, 

W= 1.36 IP, 



and 



1.36 



Rubber valves may be used for cold water, but brass, rubber composition, 
or other suitable material is required for hot water or oil. 

If a new pump will not start, it may be due to its imperfect connections or 
temporary stiffness of pump. 

Unless the suction lift and length of supply pipe be moderate, a foot-valve, 
a charging connection, and a vacuum chamber are desirable. The suction- 
pipe must be entirely free from air leakage. If the pump refuses to start 
lifting water with full pressure on, on account of the air in the pump-cham- 
ber not being dislodged, but only compressed each stroke, arrange for run- 
ning without pressure until the air is expelled and water flows. This is 
done with a check-valve in the delivery-pipe, and a waste delivery which 
may be closed when water flows. 

c P 5 mI !l i,lg ' I F ot Water. — With a free suction-pipe, any good pump 
fitted with metal valves and with hot-water packing will pump water hav- 
ing a temperature of 212°, or higher, if so placed that the water will flow 
into it. 

Robert D. Kinney, in "Power," gives the following formula for deter- 
™™g to what height water of temperatures below the boiling point can 
be lifted by suction. 

D == lift in feet, 

A = absolute pressure on surface of water ; if open to air = 14.7 lbs. 
B and W= constants. See table. 

* = ^.r^x.o 8=1I , 2 ^. 



864 



STEAM. 



Water Temp. 
Degrees F. 


B. 


W. 


Water Temp. 
Degrees F. 


B. 


W. 


40 


0.122 


62.42 


130 


2.215 


61.56 


50 


0.178 


62.41 


140 


2.879 


61.39 


60 


0.254 


62.37 


150 


3.708 


61.20 


70 


0.360 


62.31 


160 


4.731 


61.01 


80 


0.503 


62.22 


170 


5.985 


60.80 


90 


0.693 


62.12 


180 


7.511 


60.59 


100 


0.942 


62.00 


190 


9.335 


60.37 


110 


1.267 


61.87 


200 


11.526 


60.13 


120 


1.685 


61.72 


210 


14.127 


59.89 



Speed of Water through Pump-Passages and Valves. 



Tlie speed of water flowing through pipes and passages in pumps varies 
from 100 to 200 feet per minute. The loss from friction will be considerable 
if the higher speed is exceeded. 

Tbe area of valves should be sufficient to permit the water to pass at a 
speed not exceeding 250 feet per minute. 

The amount of steam which an average engine will require per indicated 
horse-power is usually taken at 30 pounds. It varies widely, however, from 
about 12 pounds in the best class of triple expansion condensing engines up 
to considerably over 90 pounds in many direct-acting pumps. Where an 
engine is overloaded or underloaded more water per horse-power will be re- 
quired than when operated at rated capacity. Horizontal tubular boilers 
will evaporate on an average from 2 to 3 pounds of water per square foot 
heating-surface per hour, but may be forced up to 6 pounds if the grate sur- 
face is too large or the draught too great for economical working. 



Sizes of Direct-acting* .Pumps. 

The two following tables are selected as representing the two common 
types of direct-acting pump, viz., the single-cylinder and the duplex. 



Efficiency of Small Direct-acting* Pumps. 



In "Reports of Judges of Philadelphia Exhibition," 1876, Group xx., 
Chas. E. Emery says : " Experiments made with steam-pumps at the Amer- 
ican Institute Exhibition of 1867 showed that average size steam-pumps do 
not, on the average, utilize more than 50 per cent of the indicated power in 
the steam cylinders, the remainder being absorbed in the friction of the en- 
gine, but more particularly in the passage of the water through the pump. 
Again, all ordinary steam-pumps for miscellaneous use, require that the 
steam-cylinder shall have three to four times the area of the water-cylinder 
to give sufficient power when the steam is accidentally low ; hence, as such 
pumps usually work against the atmospheric pressure, the net or effective 
pressure forms a small percentage of the total pressure, which, with the 
large extent of radiating surface exposed and the total absence of expansion, 
makes the expenditure of steam very large. One pump tested required 120 
pounds weight of steam per indicated horse-power per hour, and it is be- 
lieved that the cost will rarely fall below 60 pounds ; and as only 50 per 
cent of the indicated power is utilized, it may be safely stated that ordinary 
steam pumps rarely require less than 120 pounds of steam per hour for each 
horse-power utilized in raising water, equivalent to a duty of only 15,000.000 
foot pounds per 100 pounds of coal. With larger steam-pumps, particularly 
when they are proportioned for the work to be done, the duty will be mate- 
rially increased. 



PUMPS. 



865 



Sing-le-Cylinder Direct-acting- Pump. 

(Standard Sizes for ordinary service.) 



.5 


g 






03 

ft 
to 
<S 
M 












Diameter of 




T3 

.5 


■d 
g 


A 




p 


Capacity 


<D 

A 


CO 

CD 










I 


>5 

5 


A 

CD 


6 

■8 


0Q 

o 
u 

<v 


per 
Minute 

at 
Given 


.5 

A 

tab 

a 

CD 

as 

CD 


A 

CD 

.3 


















CD 

o 

U • 
CD m 
£> CD 

2g 


o 

£> CO 


o 
oq 
o 
A 
"& 
cd 


o 
u 

0Q 

<o 

ft 

cc 
O 


g 

1 

5 <p 
11 


Speed. 

& o 

u ^ 


"8 


cd 
a 

g 


CD 
ft 

CO 


6 

ft 

o 
pi 


cd 

ft 

s 

i 

cc 


P 


A 


Hi 


o 


% 


m 


O 


m 


H 


OQ 


H 


m 


s 


4 


34 


5 


.14 


300 


130 


18 


33 


91 


! 


3 


2 


1J 


4 


4 


5 


.27 


300 


130 


35 


33 


9! 


! 


1 


2 


ii 


5 


4 


7 


.39 


300 


125 


49 


45! 


15 


1 

| 


1 


3 


2! 


5! 


5 


7 


.51 


275 


125 


64 


45| 


15 


1 


3 


2! 
2! 


5£ 


5| 


7 


.72 


275 


125 


90 


45! 


15 


1 


3 


7 


7 


10 


1.64 


250 


110 


180 


58 


17 


l 4 


li 


5 


4 


7i 


n 


10 


1.91 


250 


110 


210 


58 


17 


l 


H 


5 


4 


7J 


8 


10 


2.17 


250 


110 


239 


58 


17 


l 


i* 


5 


4 


8 


6 


12 


1.47 


250 


100 


147 


67 


20! 


l 


1! 


4 


4 


8 


7 


12 


2.00 


250 


100 


200 


67 


20| 


l 


H 


5 


4 


8 


8 


12 


2.61 


250 


100 


261 


68 


30 


l 


H 


5 


5 


8 


10 


12 


4.08 


250 


100 


408 


68 


20! 


l 


il 


8 


8 


10 


8 


12 


2.61 


250 


100 


261 


68! 
68! 


30 


l* 


2 


5 


5 


10 


10 


12 


4.08 


250 


100 


408 


30 


n 


2 


8 


8 


10 


12 


12 


5.87 


250 


100 


587 


68* 


30 


H 


o 


8 


8 


12 


10 


12 


4.08 


250 


100 


408 


04 


24 


2 


2i 


8 


8 


12 


10 


18 


6.12 


200 


70 


428 


68! 


30 


2 


2! 


8 


8 


12 


12 


12 


5.87 


250 


100 


587 


64 


28! 


2 


2! 


8 


8 


12 


12 


18 


8.80 


175 


70 


616 


88 


28! 


2 


2! 


8 


8 


12 


14 


18 


12.00 


175 


70 


840 


88 


28! 


2 


2! 


8 


8 


14 


10 


12 


4.08 


250 


100 


408 


69 


30^ 


2 


2! 


8 


8 


14 


10 


18 


6.12 


175 


70 


428 


93 


25 


2 


2| 


8 


8 


14 


10 


24 


8.16 


150 


50 


408 


112 


26 


2 


2! 


8 


8 


14 


12 


12 


5.87 


250 


100 


587 


69 


30 


2 


2! 


8 


8 


14 


12 


18 


8.80 


175 


70 


616 


88 


28! 


2 


2! 


8 


8 


14 


12 


24 


11.75 


150 


50 


587 


112 


26 


2 


S 


10 


8 


14 


14 


24 


15.99 


150 


50 


800 


112 


34 


2 


12 


10 


14 


16 


16 


13.92 


175 


80 


1114 


84 


34 


2 


2* 


12 


10 


14 


16 


24 


20.88 


150 


50 


1044 


112 


38 


2 


2! 


12 


10 


16 


14 


18 


12.00 


175 


70 


840 


89 


27 


2 


2! 


8 


8 


16 


14 


24 


15.99 


150 


50 


800 


109 


34 


2 


2! 


12 


10 


16 


16 


16 


13.92 


175 


80 


1114 


85 


34 


2 


2! 


12 


10 


16 


16 


24 


20.88 


150 


50 


1044 


115 


34 


2 


2! 


12 


10 


16 


18 


24 


26.43 


125 


50 


1322 


115 


40 


2 


2! 


14 


12 


18 


16 


24 


20.88 


125 


50 


1044 


118 


38 


3 


3! 


12 


10 


18 


18 


24 


26.43 


125 


50 


1322 


118 


40 


3 


4 


14 


12 


18 


20 


24 


32.64 


125 


50 


1632 


118 


40 


3 


3! 


16 


14 


20 


18 


24 


26.43 


125 


50 


1322 


118 


40 


3 


3! 


14 


12 


20 


20 


24 


32.64 


125 


50 


1632 


118 


40 


3 


3! 


16 


14 


20 


22 


24 


39.50 


125 


50 


1975 


120 


40 


3 


'4 


18 


14 



■■ 



866 



STEAM. 



Duplex-Cylinder Direct- acting- Pump. 

(Standard sizes for ordinary service.) 













a a 

CD 3 

Cd 

!1 

33 co 
•d «« 

9 « m 

33 33_g 

£s ? 
"33 s -3 

-S053 


- o . 
do£ 

CDO, S 

u 53 <* 
CD-w-^ 

£?£ 

«H CDI— 

lis 


Sizes of Pipes for 


u 

CD 

-d 

fl 

% 

9 

1 

CD 
CO 
m 

O 

S§ 

cD,d 

2 2 


33 

1=1 

s 

CD 

o 
53 oa 

-u. CD 

2 A 

2 ° 

3 ^ 


m 

CD 

A 
o 

a 

1 

co 

o 

1? 
53 


CD 
ft 
ce ■ 

•S CD 
<D<H 

2° 

© <D 

&£ 

.202 


"a£ 

CD.'S 3 
fi f (« 

t! ^ 

53 5 3 

&> =« 

* s ^ 

CD cd^ 

a a. 3 
go,* 


Short Lengths. 

To be Increased as 
Length Increases. 


CD 

a 

2 

CD 


CD 

5 

CO 

d 


CD 
ft 

s 

a 
o 

o 

j3 


6 

a 

CD 

,d 

CD 


s 


a 


hI 


A 


Ah 


O 


A 


cc 


w 


CO 


A 


3 


2 


3 


.04 


100 to 250 


8 to 20 


n 


3 


4 


ii 


1 


4* 


2| 


4 


.10 


100 ' 


200 


20" 40 


4 


i 


1 


2 


if 


5i 


3* 


5 


.20 


100 ' 


200 


40" 80 


5 


!! 


24 


6 


4 


6 


.33 


100 ' 


150 


70" 100 


5f 


i 


3 


2 


74 


4* 


6 


.42 


100 ' 


150 


85 ; ' 125 


6| 


i* 
14 


2 


4 


3 


74 


5 


6 


.51 


100 : 


150 


100" 150 


7 


2 


4 


3 


n 


44 


10 


.69 


75 ' 


125 


100" 170 


6| 


H 


2 


4 


3 


9 


5i 


10 


.93 


75 ' 


125 


135" 230 


74 


2 


24 


4 


3 


10 


6 


10 


1.22 


75 ' 


125 


180" 300 


8+ 


2 


24 


5 


4 


10 


7 


10 


1.66 


75 ' 


125 


245" 410 


H 


2 


24 


6 


5 


12 


7 


10 


1.66 


75 ' 


125 


245" 410 


9£ 


24 


3 


6 


5 


14 


7 


10 


1.66 


75 ' 


125 


245" 410 


9£ 


24 


3 


6 


5 


12 


84 


10 


2.45 


75 ' 


125 


365" 610 


12 


i 


3 


6 


5 


14 


84 


10 


2.45 


75 ' 


125 


365" 610 


12 


3 


6 


5 


16 


8* 


10 


2.45 


75 ' 


125 


365" 610 


12 


24 


3 


6 


5 


m 


8* 


10 


2.45 


75 ' 


125 


365" 610 


12 


3 


3£ 


6 


5 


20 


8* 


10 


2.45 


75 ' 


125 


365" 610 


12 


4 


5 


6 


5 


12 


10i 


10 


3.57 


75 ' 


125 


530" 890 


141 


24 


3 


8 


7 


14 


10i 


10 


3.57 


75 ' 


125 


530" 890 


14i 


2* 


3 


8 


7 


16 


104 


10 


3.57 


75 ' 


125 


530" 890 


14i 
14i 
14i 


24 


3 


8 


7 


18J 


10i 


10 


3.57 


75 ' 


125 


530" 890 


3 2 


34 


8 


7 


20 


10i 


10 


3.57 


75 ' 


125 


530" 890 


4 


5 


8 


7 


14 


12 


10 


4.89 


75 ' 


125 


730 " 1220 


17 


24 


3 


10 


8 


16 


12 


10 


4.89 


75 ' 


125 


730 "1220 


17 


24 


3 


10 


8 


18* 


12 


10 


4.89 


75 ' 


125 


730 " 1220 


17 


3 


34 


10 


8 


20 


12 


10 


4.89 


75 ' 


125 


730 " 1220 


17 


4 


5 


10 


8 


184 


14 


10 


6.66 


75 ' 


125 


990 "1660 


19| 
19| 


3 


34 


12 


10 


20 


14 


10 


6.66 


75 ' 


122 


990 "1660 


4 


5 


12 


10 


17 


10 


15 


5.10 


50 ' 


100 


510 " 1020 


14 


3 


34 


10 


8 


20 


12 


15 


7.34 


50 ' 


100 


730 " 1460 


17 


4 


5 


12 


10 


20 


15 

15 


15 
15 


11.47 
11.47 


50 ' 


100 


1145 " 2290 
1145 " 2290 


21 
21 










25 


50 ' 


100 











Let 



IXJECTORS. 

Live Steam Injectors. 

W= water injected in pounds her hour. 

P = steam pressure in pounds per square inch. 

D ■=. diameter of throat in inches. 

T= diameter of throat in millimeters. 



INJECTORS. 



867 



Then fF=1280Z> 2 Vp 

= ].98rf 2 Vp 

The rule given by Rankine, " Steam Engine," p. 477, for finding the proper 
sectional area in square inches for the narrowest part of the nozzle is as 
follows : 

cubic feet per hour gross feed-water 

area = ., 

800 ^pressure m atmospheres 

The expenditure of steam is about one-fourteenth the volume of water 
injected. 

The following table gives the water delivered for different sizes of injec- 
tors at different pressures ; but when the injector has to lift its water a de- 
duction must be made varying from 10 to 30 per cent according to the lift. 

Deliveries for live Steam Injectors. 



a 

o 






Pressure of Steam. 






1 


« OD 




















1 






S'oo 


5~5 


30 lbs. 


60 lbs. 


80 lbs. 100 lbs. 


120 lbs. 


140 lbs. 


S 5P 


£s 






| 






=H ^ 














ss 


•>£3 












CO 




Delh 


r ery in Gallons per Hour. 




CO 
















In. 


2 


43 


61 


71 


80 


87 


93 


i 

2 


3 


97 


138 


160 


178 


196 


211 


| 


4 


173 


246 


285 


317 


348 


376 


1 


5 


272 


385 


445 


496 


545 


587 


1 


e 


392 


555 


640 


715 


783 


846 


li 


7 


533 


755 


871 


973 


1067 


1152 


li 


8 


696 


985 


1137 


1272 


1393 


1505 


H 


9 


882 


1247 


1440 


1610 


1763 


1905 


1* 


10 


1088 


1540 


1777 


1987 


2177 


2352 


2 


11 


1317 


1863 


2150 


2405 


2633 


2846 


2 


12 


1567 


2217 


2560 


2861 


3136 


3387 


2i 


13 


1840 


2602 


3005 


3358 


3680 


3975 


21 


14 


2133 


3018 


3485 


3895 


4267 


4610 


2t 


15 


2450 


3465 


4000 


4471 


4900 


5292 


2l 


16 


2787 


3942 


4551 


5087 


5575 


6022 


1 


17 


3146 


4450 


5138 


5743 


6291 


6798 


18 


3527 


4990 


5760 


6438 


7055 


7633 


2| 


19 


3930 


5560 


6418 


7175 


7861 


8492 


2f 


20 


4355 


6160 


7110 


7950 


8710 


9410 


3 



1 millimeter = 5 V inch, nearly. 



As the vertical distance the injector lifts is increased, a greater steam 
pressure is required to start the injector, and the highest steam pressure at 
which it will work is gradually decreased. 

If the feed-water is heated a greater steam pressure is required to start 
the injector, and it will not work with as high steam pressure. 

The capacity of an injector is decreased as the lift is increased or the feed- 
water heated. 

Performance of Injectors. — W. Sellers & Co. state that one of 
their injectors delivered 25.5 lbs. water to a boiler per pound of steam ; 
steam pressure 65 lbs.; temperature of feed, 64° F. 

Schaeffer & Budenberg state that their injectors will deliver 1 gallon 
water to a boiler for from 0.4 to 0.8 lbs. steam. Thev also state that the 
temperatures of feed-water taken by their injector, if non-lifting or at a 
low lift, can be as follows : 



868 STEAM. 



Pressure, lbs. . 35 to 45, 50 to 85, 90, 105, 120, 135, 150. 

Temperature, °F., 144 to 136, 133 to '130, 129, 122, 118 to 113, 109 to 105, 104 to 100. 

The Hayden & Derby Mfg. Co. state that the results given below are from 
actual tests of Metropolitan Double-Tube Injectors. 

With Cold Feed-Water. 

r>n o 9 f™t lift • J Starts with 14 lbs. steam pressure. 

un a z-ioot nit . | Works up to 250 lbs. steam pressure. 

n „ „,, o ?„„* i: ft . ( Starts with 23 lbs. steam pressure. 

un an 8-root nit . ^ Works up to 220 lbs. steam pressure. 

On a 14-foot lift : §Jarts with 27 lbs steam pressure. 

( Works up to 175 lbs. steam pressure. 



On a 20-foot lift 



| Starts with 42 lbs. steam pressure. 
| Works up to 135 lbs. steam pressure. 



Whpn nnt lifting • * Starts with 14 lbs. steam pressure. 

When not lifting . ^ Workg up tQ 25Q lbg gtea ^ preggure> 

With Feeri'lVater at 100° F. 

r»^ o o f™t lift • ( Starts with 15 lbs. steam pressure. 

Un a z-root aa . ^ Works up to 210 lbs. steam pressure. 

r>„ ov, a f™t nft • i Starts with 26 lbs. steam pressure. 

Un an 8-ioot ntt . j Works up to 160 lbs. steam pressure. 

( Starts with 37 lbs. steam pressure. 

( Works up to 120 lbs. steam pressure. 

l Starts with 46 lbs. steam pressure. 

| Works up to 70 lbs. steam pressure. 

wi,™ „^ nft:„„ . i Starts witb 15 lbs. steam pressure. 

When not lifting : j Workg up to m lbg gtear £ pressure# 

With Feed-Water at 120° F. 

„ . , ,.. + ( Starts with 20 lbs. steam pressure. 

Un a 2-loot lilt : j Works up to 185 lbs. steam pressure. 

i-k o * + v-p+ J Starts with 30 lbs. steam pressure. 

Un an 8-foot nit : ^ Works up to 120 lbs. steam pressure. 

On a 14-foot lift : 



On a 14-foot lift 
On a 20-foot lift : 



( Starts with 42 lbs. steam pressure. 
| Works up to 75 lbs. steam pressure 



__ , .... . ( Starts with 20 lbs. steam pressure. 

When not lifting : j Works up to 185 lbs. steam pressure. 

With Feed- Water at 140° F. 

On a short lift, or when not lifting, this injector will work with steam 
pressures from 20 lbs. to 120 lbs., and on an 8-foot lift with steam pressures 
from 35 lbs. to 70 lbs. x . 

Fxhaust injectors working with exhaust steam from an engine, at 
about atmospheric pressure will deliver water against boiler pressure not 
exceeding 80 lbs. per square inch. The temperature of the water may be as 
high as 190° F., while 12 per cent of the water delivered will be condensed 
steam. For pressures over 80 lbs. it is necessary to supplement the exhaust 
steam with a jet of live steam. 

Injector vs. I»nnip for Feeding* Boilers. 

The relative value of injectors, direct-acting steam pumps, and pumps 
driven from the engine, is a question of importance to all steam-users. The 
following table (" Stevens Indicator," 1888) has been calculated by D. S. 
Jacobs, M. E., from data obtained bv experiment. It will be noticed that 
when feeding cold water direct to boilers, the injector has a slight economy, 
but when feeding through a heater a pump is much the most economical. 



INJECTORS. 



869 



Method of Supplying Feed-Water 


Relative Amount 


Saving of Fuel 


to Boiler. 


of Coal Required 


over the 




per Unit of Time, 


Amount 


Temperature of Feed-Water as 
delivered to the Pump or to the 


the Amount for a 


Required 


Direct-Acting 


when the 


Injector, 60° F. Rate of Evap- 


Pump, Feeding 


Boiler is Fed by 


oration of Boiler, 10 lbs. of 


Water at 6(P, with- 


a Direct- 


Water per pound of Coal from 


out a Heater, being 


Acting Pump 


and at 212° F. 


taken as Unity. 


without Heater. 


Direct-acting pump feeding water 
at 60°, without a heater .... 






1.000 


.0 


Injector feeding water at 150°, 






without a heater 


.985 


1.5 per cent. 


Injector feeding through a heater 






in which the water is heated 






from 150° to 200° 


.938 


6.2 


Direct-acting pump feeding water 






through a heater, in which it is 






heated from 60° to 200° .... 


.879 


12.1 " 


Geared pump, run from the engine, 






feeding water through a heater, 






in which it is heated from 60° to 






200° 


.868 


13.2 " 







Sizes for Feed-Water JPipes. 

Three and six-tenths gallons of feed-water are required for each h. p. per 
hour. This makes 6 gallons per minute for a 100 h. p. boiler. In proportion- 
ing pipes, however, it is well to remember that boiler-work is seldom per- 
fectly steady, and that as the engine cuts off just as much steam as the work 
demands at each stroke, all the discrepancies of demand and supply have to 
be equalized in the boiler. Therefore we may often have to evaporate dur- 
ing one-half hour 50 to 75 per cent more than the normal requirements. For 
this reason it is sound policy to arrange the feed-pipes so that 10 gallons 
per minute may flow through them, without undue speed or friction, fox- 
each 100 h. p. of boiler capacity. The following tables will facilitate this 
work. 

Table Giving- Rate of Flow of Water, in Feet per 71 i mute. 

Through JPipes of Various Sizes, for Varying 

(Quantities of Flow". 



Gallons ? 
per Min. ^ 


in 


lin. 


lj in. 


ljin. 


2 in. 


2Jin. 


3 m. 


4 in. 


5 


218 


122*. 


78* 


54*. 


30* 


19* 


13J 


7§ 


10 


43( 


245 


157 


109 


61 


38 


27 


15* 


15 


653 


367* 


235* 


163* 


91*. 


58*. 


40*. 


23 


20 


ST- 


490 


314 


218 


122 


78 


54 


30f 


25 


090 


612* 


392* 


2721 


152*. 


97*. 


67* 


38* 


30 




735 


451 


327 


183 


117 


81 


46 


35 




857* 


549*. 


381*. 


213* 


136* 


94*, 


53| 


40 




980 


628 


436 


244 


156 


108 


61* 


45 




1102* 


706* 


490* 


274* 


175* 


121*. 


69 


50 






785 


545 


305 


195 


135 


76§ 


75 






1177*. 


817* 


457*. 


292* 


202* 


115 


100 








1090 


610 


380 


270 


153* 


125 










762* 


487* 


337* 


191| 


150 










915 


585 


405 


230 


175 










1067* 


682*. 


472* 


268* 
306| 


200 










1220 


780 


540 



870 



STEAM. 



Table Civing- Loss in Pressure due to friction, in Pounds 
per Square Inch, for Pipe lOO ITeel JLong-. 









(By G. A. Ellis, 


C. E.) 








Gallons 


















Dis- 
charged 


fin. 


lin 


li in. 


ljin. 


2 in. 


2|in. 


3 in. 


4 in. 


per Min. 


















5 


3.3 


0.84 


0.31 


0.12 










10 


13.0 


3.16 


1.05 


0.47 


0.12 








15 


28.7 


6.98 


2.38 


0.97 










20 


50.4 


12.3 


4.07 


1.66 


0.42 








25 


78.0 


19.0 


6.40 


2.62 




0.21 


0.10 




30 




27.5 


9.15 


3.75 


0.91 








35 




37.0 


12.4 


5.05 










40 




48.0 


16.1 


6.52 


1.60 








45 






20.2 


8.15 










50 






24.9 


10.0 


2.44 


0.81 


0.35 


0.09 


75 






56.1 


22.4 


5.32 


1.80 


0.74 




100 








39.0 


9.46 


3.20 


1.31 


0.33 


125 










14.9 


4.89 


1.99 




150 










21.2 


7.0 


2.85 


0.69 


175 










28.1 


9.46 


3.85 




200 










37.5 


12.47 


5.02 


1.22 



lioss of Head due to Bends. 

Bends produce a loss of head in the flow of water in pipes. Weisbach 
gives the following formula for this loss : 
v 2 

H=f — where H= loss of head in feet, f — coefficient of friction,?; r= ve- 
locity of flow in feet per second, g — 32.2. 

As the loss of head or pressure is inmost cases more conveniently stated in 
pounds per square inch, we may change this formula by multiplying by 
0.433, which is the equivalent in pounds per square inch for one foot head. 

If P =. loss in pressure in pounds per square inch, F = coefficient of fric- 
tion. 



P= F ^—, v being the same as before. 

From this formula has been calculated the following 
corresponding to various exterior angles, A. 


table of values for F, 


A — 
F = 


20° 
0.020 


40° 
0.060 


45° 
0.079 


60° 
0.158 


80° 
0.320 


90° 
0.426 


100° 
0.546 


110° 
0.674 


120° 
0,806 


130° ' 
0.934 



This applies to such short bends as are found in ordinary fittings, such as 
90° and 45° Ells, Tees, etc. 

A globe valve will produce a loss about equal to two 90° bends, a straight- 
way valve about equal to one 45° bend. To use the above formula find the 
speed p. second, being one-sixtieth of that found in Table p. 869 ; square this 
speed, and divide the result by 64.4; multiply the quotient by the tabular 
value of'F corresponding to the angle of the turn, A. 

For instance, a 400 h.p. battery of boilers is to be fed through a 2-inch pipe. 
Allowing for fluctuations we figure 40 gallons per minute, making 244 feet 
per minute speed, equal to a velocity of 4.6 per second. Suppose our pipe is 
in all 75 feet long ; we have from Table No. 36, for 40 gallons per minute, 
1.60 pounds loss ; for 75 feet we have only 75 per cent of this = 1.20 pounds. 
Suppose we have 6 right-angled ells, each giving F = 0.426. We have then 
4.0G x 4.06 — 16.48 ; divide this by 64.4 = 0,256. Multiply this by F= 0.426 



INJECTORS. 871 



pounds, and as there are 6 ells, multiply again by 6, and we have 6 x 0.426 x 
0.256 = 0.654. The total friction in the pipe is therefore 1.20 -f- 0.654 = 1.854 
pounds per square inch. If the boiler pressure is 100 pounds and the water 
level in the boiler is 8 feet higher than the pump suction level, we have first 
8 X 0.433 = 3.464 pounds. The total pressure on the pump plunger then is 
100 -f- 3.464 -f- 1.854= 105.32 pounds per square inch. If in place of 6 right- 
angled ells we had used three 45° ells, they would have cost us only 3 X 
0.079 = 0.237 pounds ; 0.237 X 0.256 = 0.061. 

The total friction head would have been 1.20 + 0.061 = 1.261, and the total 
pressure on the plunger 100 -+- 3.464 -f 1.261 = 104.73 pounds per square inch, 
a saving over the other plan of nearly 0.6 pounds. 

To be accurate, we ought to add a certain head in either case, " to produce 
the velocity." But this is very small, being for velocities of : 

2; 3; 4; 5; 6; 8; 10; 12 and 18 feet per sec. 

0.027; 0.061; 0.108; 0.168 ; 0.244 ; 0.433; 0.672 ; 0.970 and 2.18 lbs. per sq. in. 

Our results should therefore have been increased by about 0.11 pounds. 

It is usual, however, to use larger pipes, and thus to materially reduce the 
fractional losses. 

JFeed- Water Heaters are of the " open" or " closed" type. 

The open heater is usually made of cast iron, as this material will with- 
stand the corrosive action of acids found in feed-waters better than any 
other metal. In this type of heater tbe exhaust steam from engines and 
pumps, and the feed-water broken up into drops by suitable means, are 
brought into immediate contact, and the steam not condensed in heating 
the water passes off to the atmosphere. The quantity of water that can be 
heated is only limited by the amount of steam and water that can be 
brought together. The steam condensed in heating the water is saved and 
utilized for boiler feed. An open heater should be provided with an effi- 
cient oil-separator, a large settling-chamber or hot well in wbich, if desired, 
a filtering bed of suitable material can be placed to insure the removal from 
the water, of all the impurities held in suspension, a device for skim- 
ming the surface of the water to remove the impurities floating on the water, 
and a large blow-off opening placed at the lowest point in the heater. 

The closed heater is made with a wrought-iron or steel cylindrical shell 
and cast- or wrought-iron heads, having iron or brass tubes inside, set in 
tube plates so as to make steam- and water-tight joints, provision being made 
for the expansion and contraction of the tubes. According to the particular 
design of the heater, the exhaust steam passes through or around the tubes, 
the water being on the opposite of the walls of the tubes. The steam and 
water are separated by metal through which the beat of the exhaust steam 
is transmitted to the water. As an oil-separator is very seldom attached to 
a closed heater, the steam condensed in heating the water is wasted. The 
quantity of water that can be heated is limited by the amount of heat that 
can be transmitted through the tubes. The efficiency of heat transmission 
is decreased by the coating of oil that covers the steam side, and the crust 
of scale that coats the water side of the tubes. No provision can be made 
for purifying the water in a closed heater, as the constant circulation of the 
water prevents the impurities from settling. The impurities that are in the 
water pass on into the boiler. Purification must be done by means of an 
auxiliary apparatus. 

Saving- \*j Heating- Feed- Water. 

(W. W. Christie.) 

In converting water at 32° F. into steam at atmospheric pressure, it must 
be raised to 212° F., the boiling point. 

The specific heat of water varies somewhat with its temperature, so that to 
raise a pound of water from 32° to 212° F. or 180° F., requires 180.8 heat 
units. 

To convert it into steam, after it has reached 212° F., requires 965.8 heat 
units, or in all 180.8 -f 965.8 = 1146.6 units of heat, thermal units. 

The saving to be obtained by the use of waste heat, as exhaust steam, 
heating the water by transfer of some of its heat through metal walls, is 
calculated by this formula : 



872 



STEAM. 



Gain in per cent 



100 (h 2 — hj) _ 100 (t 2 — t t ) 



H—ht 



H— t x -f 32 



very nearly, 



in which. H = total heat in steam at boiler pressure (above that in water at 
32° F.) in B. T. U. 

h 2 = heat iii feed-water (above 32° F.) after heating. 

hy = heat in feed- water (above 32° F.) before beating. 

t. 2 = temperature of feed-water after heating °F. 

t\ = temperature of feed-water before heating °F. 
given H= 1146.6, U = 212, t t = 112, or a difference of 100°; and we obtain by 
use of the above formula, gain in per cent = 9.37, or for 10° approximately 
.937 per cent, for 11° 1.02 per cent, so we may say that for every 11° F. added 
to the feed-water temperature by use of the exhaust steam, 1 per cent of 
fuel saving results. 
The table which follows is taken from " Power." 

Percentage of Saving' in Fuel l»y Heating* J?eed-Water wy 
Waste Steam, Steam at *© Pounds Oauge Pressure. 



—1 V 
& U 

'-3 3 








Temperature of Water Entering Boiler. 






120° 


130° 


140° 


150° 


160° 


170° 


180° 


190° 


200° 


1 
210° 1 220° 


250° 


35° 


7.24 


8.09 


8.95 


9.89 


10.66 


11.52 


12.38 


13.24 


14.09 


14.95 


15.81 


19.40 


40° 


6.84 


7.69 


8.56 


9.42 


10.28 


11.14 


12.00 


12.87 


13.73 


14.59 


15.45 


18.89 


45° 


6.44 


7.30 


8.16 


9.03 


9.90 


10.76 


11.62 


12.49 


13.36 


14.22 


15.09 


18.37 


50° 


6.03 


6.89 


7.76 


8.64 


9.51 


10.38 


11.24 


12.11 


12.98 


13.85 


14.72 


17.87 


55° 


5.63 


6.49 


7.37 


8.24 


9.11 


9.99 


10.85 


11.73 


12.60 


13.48 


14.35 


17.38 


60° 


5.21 


6.08 


6.96 


7.84 


8.72 


9.60 


10.47 


11.34 


12.22 


13.10 


13.98 


16.86 


65° 


4.80 


5.67 


6.56 


7.44 


8.32 


9.20 


10.08 


10.96 


11.84 


12.72 


13.60 


16.35 


70° 


4.38 


5.26 


6.15 


7.03 


7.92 


8.80 


9.68 


10.57 


11.45 


12.34 


13.22 


15.84 


75° 


3.96 


4.84 


5.73 


6.62 


7.51 


8.40 


9.28 


10.17 


11.06 


11.95 


12.84 


15.33 


80° 


3.54 


4.42 


5.32 


6.21 


7.11 


8.00 


8.88 


9.78 


10.67 


11.57 


12.46 


14.82 


85° 


3.11 


4.00 


4.90 


5.80 


6.70 


7.59 


8.48 


9.38 


10.28 


11.18 


12.07 


14.32 


90° 


2.68 


3.58 


4.48 


5.38 


6.28 


7.18 


8.07 


8.98 


9.88 


10.78 


11.68 


13.81 


95° 


2.25 


3.15 


4.05 


4.96 


5.86 


6.77 


7.66 


8.57 


9.47 


10.38 


11.29 


13.31 


100° 


1.81 


2.71 


3.62 


4.53 


5.44 


6.35 


7.25 


8.16 


9.07 


9.98 


10.88 


12.80 



Pump Exhaust. 

In many plants the only available exhaust steam comes from the steam 
pumps used for elevator service, boiler-feeding, etc. ; or in condensing plants 
from the air-pumps, water-supply, and boiler feed-pumps. It should also be 
remembered that all direct-acting steam pumps are large consumers of 
steam, taking several boiler h. p. for each indicated h. p., and that the ex- 
haust steam from them will heat about six times the same quantity by weight 
of cold water, from 50° to 212° F., and that these pumps, orthe independent 
condenser pumps, are more economical when all the exhaust from them is 
used for heating feed-water than the best kind of triple expansion condens- 
ing engines. With the pumps all the heat not used in doing work can be 
conserved and returned to the boiler in the feed-water, whereas even with 
triple expansion engines at least 80 per cent of the total heat in the steam is 
carried away in the condensing water. 

While the supply of exhaust from these pumps may not be sufficient to 
raise the temperature to the highest point, yet the saving is large and con- 
stant. 

These results do not take any account of the purifying action in the 
"open" heaters on the feed-water, the improved condition of which, by di- 
minishing the average deposit within the boiler, materially increases both 
the boiler capacity and the economy ; while the more uniform temperature 



FUEL ECONOMIZER. 



873 



accompanying the use of a hot feed reduces the repairs and lengthens the 
life of all boilers. 

If the quantity of water passing through the heater is only what is re- 
quired to furnish steam for the engine from which the exhaust comes, more 
than four-fifths of this exhaust steam will remain uncondensed, and will 
thus become available for other purposes, such as heating buildings, dryer 
systems, etc. ; in which case the returns can be sent back to the boiler by 
suitable means. 

FVEI £CO!OMIZ£R§. 

Performance of a Green Economizer with a Smoky Coal. 



(D. K. Clark, S. E., p, 



From tests by M. W. Grosseteste, covering a period of three weeks on a 
Green economizer, using a smoke-making coal, with a constant rate of com- 
bustion under the boilers, it is apparent that there is a great advantage in 
cleaning the pipes daily — the elevation of temperature having been in- 
creased by it from 88° to 153°. In the third week, without cleaning, the ele- 
vation of temperature relapsed in three days to the level of the first week ; 
even on the first day it was quickly reduced by as much as half the extent 
of relapse. By cleaning the pipes daily an increased elevation of tempera- 
ture of 65° F. was obtained, whilst a gain of 6% was effected in the evapora- 
tive efficiency. 

The action of Green's economizer was tested by M. W. Grosseteste for a 
period of three weeks. The apparatus consists of four ranges of vertical 
pipes, 6£ feet high, 3| inches in diameter outside, nine pipes in each range, 
connected at top and bottom by horizontal pipes. The water enters all the 
tubes from below, and leaves them from above. The system of pipes is 
enveloped in a brick casing, into which the gaseous products of combustion 
are introduced from above, and which they leave from below. The pipes 
are cleared of soot externally by automatic scrapers. The capacity for 
water is 24 cubic feet, and the total external heating-surface is 290 square 
feet. The apparatus is placed in connection Avith a boiler having 355 square 
feet of surface. 

Green's Economizer. — Results of Experiments on its Efficiency as Affected 
by the State of the Surface. 

(W. Grosseteste.) 





Temperature of Feed- 


Temperatnre of Gas- 




water. 


eous Products. 


Time. 














February and March. 


Enter- 


Leav- 




Enter- 


Leav- 






ing 
Feed- 


ing 


Differ- 


ing 


ing 


Differ- 




Feed- 


ence. 


Feed- 


Feed- 


ence. 




heater. 


heater. 




heater. 


heater. 






Fahr. 


Fahr. 


Fahr. 


Fahr. 


Fahr. 


Fahr. 


1st Week 


73.5° 


161.5° 


88.0° 


849° 


261° 


588° 


2d Week 


77.0 


230.0 


153.0 


882 


297 


585 


3d Week — Monday . . 


73.4 


196.0 


122.6 


831 


284 


547 


Tuesday . . 


73.4 


181.4 


108.0 


871 


309 


562 


Wednesday 


79.0 


178.0 


99.0 











Thursday . 


80.6 


170.6 


90.0 


952 


329 


623 


Friday . . 


80.6 


169.0 


88.4 


889 


338 


551 


Saturday 


79.0 


172.4 


93.4 


901 


351 


550 



1st Week. 

Coal consumed per hour 214 lbs. 

Water evaporated from 32° F. per hour 1424 
Water per pound of coal ...... 6.65 



2d Week. 3d Week. 

216 lbs. 213 lbs. 

1525 1428 

7.06 6.70 



874 



STEAM. 



The Fuel Economizer Company, Matteawan, N.Y., describe the construc- 
tion of Green's economizer, thus: The economizer consists of a series of sets 
of cast-iron tubes about 4 inches in diameter and 9 feet in length, made in 
sections (of various widths) and connected by " top " and " bottom headers," 
these again being coupled by " top " and " bottom branch pipes " running 
lengthwise, one at the top and the other at the bottom, on opposite sides 
and outside the brick chamber which encloses the apparatus. The waste 
gases are led to the economizer by the ordinary flue from the boilers to the 
chimney. 

The feed-water is forced into the economizer by the boiler pump or in- 
jector, at the lower branch pipe nearest the point of exit of gases, and 
emerges from the economizer at the upper branch pipe nearest the point 
where the gases enter. 

Each tube is provided with a geared scraper, which travels continuously 
up and down the tubes at a slow rate of speed, the object being to keep the 
external surface clean and free from soot, a non-conductor of heat. 

The mechanism for working the scrapers is placed on the top of the econ- 
omizer, outside the chamber, and the motive power is supplied either by a 
belt from some convenient shaft or small independent engine or motor. 
The power required for operating the gearing, however, is very small. 

The apparatus is fitted with blow-off and safety valves, and a space is pro- 
vided at the bottom of the chamber for the collection of the soot, which is 
removed by the scrapers. 

One boiler plant equipped with the Green economizer gave, under test, 
these results. 

The total area of heating surface in the plant was 3,126 square feet, and 
the number of tubes in the economizer 160. The results were as follows: — 



Particulars of Test. 



Econo- 


Econo- 


mizer 
working, 
Dec. 15. 


mizer not 
working, 
Dec. 16. 


11.5 

8,743 
7.5 


11.5 
9,694 

7.7 


15.2 

54,078 


16.8 

82,725 


247.0 


243.5 


68.2 


67.2 


84.2 




196.2 


82.0 


112. 


. . . 


435. 


. . . 


279. 


452.0 


156. 




9.617 


8.533 


11.204 


9.955 


12.5 





1. Duration of test hours 

2. Weight of dry coal consumed lbs. 

3. Percentage of ash and refuse . . . per cent 

4. Weight of coal consumed per hour per square 

foot grate surface lbs. 

5. Weight of water evaporated lbs. 

6. Horse-power developed on basis of 30 lbs. per 

h.p. fed at 100° and evaporated at 70 lbs., h.p. 

7. Average boiler pressure (above atmosphere), 

lbs. 

8. Average temperature of feed-water entering 

economizer deg. Fahr. 

9. Average temperature of feed-water entering 

boilers deg. Fahr. 

10. Number of degrees feed-water was heated by 

economizer deg. Fahr. 

11. Average temperature of flue gases entering 

economizer deg. Fahr. 

12. Average temperature of flue gases entering 

chimney deg. Fahr. 

13. Number degrees flue gases were cooled by econ- 

omizer deg. Fahr. 

14. Lbs. water evaporated per lb. of coal, as ob- 

served 

15. Equivalent evaporation per lb. of coal from 

and at 212° 

16. Percentage gained by using the economizer 

per cent 



The steam in this test contained 1.3 per cent of moisture. 



I UEL ECONOMIZERS, 



875 



W. S. Hutton gives the following results of tests of a steam boiler with 
and without an economizer. 



Duration of test, hours 

Weight of coal, pounds 

Steam pressure, pounds 

Temp, water entering economizer, degrees 

" " " boiler, degrees . . 

Degrees feed-water heated by economizer 
Temp, gases entering economizer, degrees 

" " " chimney, degrees . 

Degrees gases cooled by economizer . . 
Evaporation per lb. coal, from and at 212°, pounds 
Saving by economizer, per cent . . . 



With Econ- 
omizer. 



m 

7856 

58 

88 
225 
137 
618 
365 
253 

10.613 

28.9 



Without 
Econo- 
mizer. 



11* 

10282 
57 

' 85 



645 

' '8.235 



Oreeii's JPuel Economizer. — Clark gives the following average re- 
sults of comparative trials of three boilers at Wigan used with and without 
economizers : 



Coal per square foot of grate per hour 
Water at 100° evaporated per hour . 
Water at 212° per pound of coal . . 



Without 
Economizers. 

. . 21.6 
. . 73.55 
. . 9.60 



With 
Economizers. 

21.4 

79.32 

10.56 

Showing that in burning equal quantities of coal per hour the rapidity of 
evaporation is increased 9.3% and the efficiency of evaporation 10% by the 
addition of the economizer. 

The average temperature of the gases and of the feed-water before and 
after passing the economizer were as follows : 

With 6-ft. 

Before. 
Average temperature of gases ... 649 
Average temperature of feed-water . 47 

Taking averages of the two grates, to raise the temperature of the feed- 
water 100°, the gases were cooled down 250°. 



grate. 


With 4-ft. grate. 


After. 


Before. After. 


340 


501 312 


157 


41 137 



STEAM SEPARATORS. 



Carefully conducted experiments have shown that water, oil, or other 
liquids passing through pioes along with steam do not remain thoroughly 
mixed with the steam itself, but that the major portion of these liquids fol- 
lows the inner contour of the pipe, especially in the case of horizontal 
pipes. 

From this it would necessarily follow that a rightly designed separator to 
meet these conditions must interrupt the run of the liquid by breaking the 
continuity of the pipe, and offering a receptacle into which the liquid will 
flow f reeiy, or fall by gravity — that this appliance must further offer the 
opportunity for the liquid to come to rest out of the current of steam, for it 
is not enough to simply provide a well or a tee in the pipe, since the current 
would jump or draw the liquid over this opening, especially if the velocity 
was high. 

It is also evident that means must be provided in this appliance for inter- 
rupting the progress of those particles of the liquid which are traveling in 
the current of the steam, and do this in such a way that these particles will 



876 



STEAM. 



also be detained and allowed to fall into the receptacle provided, which 
receptacle must be fully protected from the action of the current of the 
steam ; otherwise, the separated particles of water or oil will be picked 
up and carried on past the separator. 

To prevent the current from jumping the liquid over the well, and to 
interrupt the forward movement of those particles traveling in or with the 
current, it follows that some obstruction must be interposed in the path of 
the current. 

Steam separators should always be placed as near as possible to the steam 
inlet to the cylinder of the engine. Oil separators are placed in the run of 
the exhaust pipe from engines and pumps, for the purpose of removing the 
oil from the steam before it is used in any way where the presence of oil 
would cause trouble. 

Prof. R. C. Carpenter conducted a series of tests on separators of several 
makes in 1891. The following table shows results under various conditions 
of moisture : 





Test with Steam of about 10% 
of Moisture. 


Tests with Varying Moisture. 


It 


Quality of 
Steam 
Before. 


Quality of 
Steam 
After. 


Efficiency 
per cent. 


Quality of 
Steam 
Before. 


Quality of 
Steam 
After. 


Average 
Efficiency. 


B 
A 
D 
C 
E 
F 


87.0% 

90.1 

89.6 

90.6 

88.4 

88.9 


98.8% 

98.0 

95.8 

93.7 

90.2 

92.1 


90.8 
80.0 
59.6 
33.0 
15.5 
28.8 


66.1 to 97 .5% 
51.9 " 98 

72.2 " 96.1 
67.1 " 96.8 
68.6 " 98.1 
70.4 " 97.7 


97.8 to 99 % 
97.9" 99.1 
95.5 " 98.2 
93.7 " 98.4 
79.3 " 98.5 
84.1 " 97.9 


87.6 
76.4 
71.7 
63.4 
36.9 
28.4 



Conclusions from the tests were : 1. That no relation existed between the 
volume of the several separators and their efficiency. 

2. No marked decrease in pressure was shown by any of the separators, 
the most being 1.7 lbs. in E. 

3. Although changed direction, reduced velocity, and perhaps centrifugal 
force are necessary for good separation, still some means must be provided 
to lead the water out of the current of the steam. 

A test on a different separator from those given above was made by Mr. 
Charles H. Parker, at the Boston Edison Company's plant, in November, 
1897, and the following results obtained : 

Length of run 3-4 hrs. 

Average pressure of steam 158 lbs. per sq. in. 

Temperature of upper thermometer in calorimeter on 

outlet of separator 368.5° F. 

Temperature of lower thermometer in calorimeter on 

outlet of separator 291.7° F. 

Normal temperature of lower thermometer, when steam 

is at rest 292.9° F. 

Degrees cooling as shown by lower thermometer . . . 1.2° F. 

Moisture in steam delivered by separator as shown by 

cooling of lower thermometer 06 per cent. 

Water discharged from separator per hour 52 lbs. 

Steam and entrained water passing through engine, as 
shown by discharge from air pump of surface con- 
denser 7359 lbs. 

Steam and entrained water entering separator .... 7411 lbs. 

Moisture taken out by separator 72 

Total moisture in steam (.06 plus .72) 78 per cent. 

Efficiency of separator ,..«.... 92.3 per cent. 



SAFETY VALVES. 877 

SAFETY VAIVEi. 
Calculation of Weiglit, etc., for Lever Safety- Valve. 

Let W= weight of ball at end of lever, in pounds ; 
to = weight of lever itself, in pounds ; 
V= w eight of valve and spindle, in pounds ; 
L = distance between fulcrum and center of ball, in inches ; 
I = distance between fulcrum and center of valve, in inches ; _ 
g = distance between fulcrum and center of gravity of lever, in inches; 
A = area of valve, in square inches ; . . 

P = pressure of steam, in pounds per square inch at which valve will 
open. 

Then PA X I = W X L + w X U + V X I ; 

WL + wg±Vl. 
whence P = -j-. ; 

itr PAl -wg—Vl m 

w= x , 

_ PAl —tog— VI 
L ~ W " 

Example. — Diameter of valve, 4 inches ; distance from fulcrum to center 
of ball, 36 inches ; to center of valve, 4 inches ; to center of gravity of lever, 
16 inches ; weight of valve and spindle, 6 lbs. ; weight of lever, 10 lbs. ; re- 
quired the weight of ball to make the blowing-off pressure 100 lbs. per 
square inch ; area of 4-inch valve =: 12.566 square inches. Then 

m PAl — wq—Vl 100 X 12.566 X 4 — 10 X 16 
W— 5r = 53 



Rules Governing- Safety-Valves. 

(Rule of U. S. Supervising Inspectors of Steam-vessels as amended 1894.) 

The distance from the fulcrum to the valve-stem must in no case be less 
than the diameter of the valve-opening ; tbe length of the lever must not be 
more than ten times the distance from the fulcrum to the valve-stem ; the 
width of the bearings of the fulcrum must not be less than three-quarters 
of an inch ; the length of the fulcrum-link must not be less than four inches; 
the lever and fulcrum-link must be made of wrought iron or steel, and the 
knife-edged fulcrum points and the bearings for these points must be made 
of steel and hardened ; the valve must be guided by its spindle, both above 
and below the ground seat and above the lever, through supports either 
made of composition (gun-metal) or bushed with it ; and the spindle must 
fit loosely in the bearings or supports. 

Lever safety-valves to be attached to marine boilers shall have an area of 
not less than 1 square inch to 2 square feet of the grate surface in the 
boiler, and the seats of all such safety-valves shall have an angle of inclina- 
tion of 45° to the center line of their axes. 

Spring-loaded safety-valves shall be required to have an area of not less 
than 1 square inch to 3 square feet of grate surface of the boiler, except as 
hereinafter otherwise provided for water-tube or coil and sectional boilers, 
and each spring-loaded valve shall be supplied with a lever that will raise the 
valve from its seat a distance of not less than that equal to one-eighth the 
diameter of the valve-opening, and the seats of all such safety-valves shall 
have an angle of inclination to the center line of their axes af 45°. All 
spring-loaded safety-valves for water-tube or coil and sectional boilers 
required to carry a steam-pressure exceeding 175 lbs. per square inch shall 
be required to have an area of not less than 1 square inch to 6 square feet 
of the grate surface of the boiler. Nothing herein shall be construed so as to 
prohibit the use of two safety-values on one water-tube or coil and sectional 
boiler, provided the combined area of such valves is equal to that required 
by rule for one such valve. 



878 



STEAM. 



Rule on Safety-Valves in Philadelphia Ordinances. — 

Every boiler when tired separately, and every set or series of boilers when 
placed over one tire, shall have attached thereto, without the interposition 
of any other valve, two or more safety-valves, the aggregate area of which 
shall have such relations to the area of the grate and the pressure within 
the boiler as is expressed in schedule A. 

Schedule A. — Least aggregate area of safety-valve (being the least sec- 
tional area for the discharge of steam) to be placed upon all stationary 
boilers with natural or chimney draught (see note a). 

22.5 G 
~ P + 8.62' 
in which A is area of combined safety-valves in inches ; G is area of grate in 
square feet ; P is pressure of steam in pounds per square inch to be carried 
in the boiler above the atmosphere. 

The following table gives the results of the formula for one square foot of 
grate, as applied to boilers used at different pressures : 

Pressures per square inch : 

10 20 30 40 50 60 70 80 90 100 110 120 150 175 

Valve area in square inches corresponding to one square foot of grate : 
1.2 .79 .58 .46 .38 .33 .29 .25 .23 .21 .19 .17 .14 .12 

[Note a.] — Where boilers have a forced or artificial draught, the inspec- 
tor must estimate the area of grate at the rate of one square foot of grate 
surface for each 16 lbs. of fuel burned on the average per hour. 

The various rules given to determine the proper area of a safety-valve do 
not take into account the effective discharge area of the valve. A correct 
rule should make the product of the diameter and lift proportional to the 
weight of steam to be discharged. 

Mr. A. G. Brown (The Indicator and its Practical Working) gives the fol- 
lowing as the lift of the lever safety-valve for 100 lbs. gauge pressure. Tak- 
ing the effective area of opening at 70 per cent of the product of the rise and 
the circumference 

Diameter of valve, inches 2 2i 3 3i 4 4£ 5 6 

Rise of valve, inches . . .0583 .0523 .0507 .0492 .0478 .0462 .0446 .043 

For " pop " safety-valves, Mr. Brown gives the following table for the 
rise, effective area, and quantity of steam discharged per hour, taking the 
effective area at 50 per cent of the actual on account of the obstruction 
which the lip of the valve offers to the escape of the steam. 



Di. valve in. 


1 


1* 


2 


2h 


3 


Zh 


4 


U 


5 


6 


Lift inches. 


.125 


.150 


.175 


.200 


.225 


.250 


.275 


.300 


.325 


.375 


Area, sq. in. 


.196 


.354 


.550 


.785 


1.061 


1.375 


1.728 


2.121 


2.553 


3.535 


Gauge- 
press. 


Steam discharged per hour, lbs. 


30 lbs. 


474 


856 


1330 


1897 


2563 


3325 


4178 


5128 


6173 


8578 


50 


669 


1209 


1878 


2680 


3620 


4695 


5901 


7242 


8718 


12070 


70 


861 


1556 


2417 


3450 


4660 


6144 


7596 


9324 


11220 


15535 


90 


1050 


1897 


2947 


4207 


5680 


7370 


9260 


11365 


13685 


18945 


100 


1144 


2065 


3208 


4580 


6185 


8322 


10080 


12375 


14895 


20625 


120 


1332 


2405 


3736 


5332 


7202 


9342 


11735 


14410 


17340 


24015 


140 


1516 


2738 


4254 


6070 


8200 


10635 


13365 


16405 


19745 


27340 


160 


1696 


3064 


4760 


6794 


9175 


11900 


14955 


18355 


22095 


30595 


180 


1883 


3400 


5283 


7540 


10180 


13250 


16595 


20370 


24520 


33950 


200 


2062 


3724 


5786 


8258 


11150 


14465 


18175 


22310 


26855 


37185 



If we also take 30 lbs. of steam per hour, at 100 lbs. gauge-pressure = 1 
h.p., we have from the above table : 

Diameter inches . 1 H 2 1\ 3 'i\ 4 4J 5 6 
Horse-power . . 38 69 107 153 206 277 336 412 496 687 



RULES FOR CONDUCTING BOILER TESTS. 



879 



A boiler having ample grate surface and strong draft may generate 
double the quantity of steam its rating calls for ; therefore in determining 
the proper size of safety-valve for a boiler this fact should be taken into 
consideration and the effective discharge of the valve be double the rated 
steam-producing capacity of the boiler. 

The Consolidated Safety-valve Co.'s circular gives the following rated 
capacity of its nickel-seat " pop " safety-valves : 



Size, in . . 


1 


H 


1* 


2 


2* 


3 


3* 


4 


U 


5 


5.i 


Boiler ( from 
H.P. 1 to 


8 


10 


20 


35 


60 


75 


100 


125 


150 


175 


200 


10 


15 


30 


50 


75 


100 


125 


150 


175 


200 


275 



RUIEi I OH COafBUCIISG BOIIER TESTS. 

The Committee of the A. S. M. E. on Boiler-tests recommended the fol- 
lowing revised code of rules for conducting boiler trials. (Trans, vol. xx.) 

Code of 1897. 
Preliminaries to a Trial. 

I. Determine at the outset the specific object of the proposed trial, whether 
it be to ascertain the capacity of the boiler, its efficiency as a steam gener- 
ator, its efficiency and its defects under usual working conditions, the econ-. 
omy of some particular kind of fuel, or the effect of changes of design, 
proportion, or operation ; and prepare for the trial accordingly. 

II. Examine the boiler, both outside and inside ; ascertain the dimensions 
of grates, heating surfaces, and all important parts ; and make a full 
record, describing the same, and illustrating special features by sketches. 
The area of heating surfaces is to be computed from the outside diameter of 
water-tubes and the inside diameter of fire-tubes. All surfaces below the 
mean water level which have water on one side and products of combustion 
on the other are to be considered water-heating surface, and all surfaces 
above the mean water level which have steam on one side and products of 
combustion on the other are to be considered as superheating surface. 

III. Notice the general condition of the boiler and its equipment, and 
record such facts in relation thereto as bear upon the objects in view. 

If the object of the trial is to ascertain the maximum economy or capa- 
city of the boiler as a steam generator, the boiler and all its appurtenances 
should be put in first-class condition. Clean the heating surface inside and 
outside, remove clinkers from grates and from sides of the furnace. Re- 
move all dust, soot, and ashes from the chambers, smoke connections, and 
flues. Close air leaks in the masonry and poorly-fitted cleaning-doors. See 
that the damper will open wide and close tight. Test for air leaks by firing 
a few shovels of smoky fuel and immediately closing the damper, observing 
the escape of smoke through the crevices, or by passing the flame of a can- 
dle over cracks in the brickwork. 

IV. Determine the character of the coal to be used. For tests of the effi- 
ciency or capacity of the boiler for comparison with other boilers the coal 
should, if possible, be of some kind which is commercially regarded as a stan- 
dard. For New England and that portion of the country east of the Allegheny 
Mountains, good anthracite egg coal, containing not over 10 per cent of ash, 
and semi-bituminous Clearfield (Pa.), Cumberland (Md.), and Pocahontas 
(Va.) coals are thus regarded. West of the Allegheny Mouutains, Poca- 
hontas (Va.), and New River (W. Va.) semi-bituminous, and Youghiogheny 
or Pittsburg bituminous coals are recognized as standards.* There is no 
special grade of coal mined in the "Western States which is widely recog- 
nized as of superior quality or considered as a standard coal for boiler test- 
ing. Big Muddy Lump, an Illinois coal mined in Jackson County, 111., is 

* These coals are selected because they are about the only coals tohich con- 
tain the essentials of excellence of quality, adaptability to various kinds of 
furnaces, grates, boilers, and methods of firing, and wide distribution and 
general accessibility in the markets. 



880 STEAM. 



suggested as being of sufficiently high grade to answer the requirements in 
districts where it is more conveniently obtainable than the other coals men- 
tioned above. 

For tests made to determine the performance of a boiler with a particular 
kind of coal, such as may be specified in a contract for the sale of a boiler, 
the coal used should not be higher in ash and in moisture than that speoi- 
fied, since increase in ash and moisture above a stated amount is apt to 
cause a falling off of both capacity and economy in greater proportion than 
the proportion of such increase. 

V. Establish the correctness of all apparatus used in the test for weighing 
and measuring. These are : 

1. Scales for weighing coal, ashes, and water. 

2. Tanks, or water meters for measuring water. Water meters, as a rule, 
should only be used as a check on other measurements. For accurate work, 
the water should be weighed or measured in a tank. 

3. Thermometers and pyrometers for taking temperatures of air, steam, 
feed-water, waste gases, etc. 

4. Pressure gauges, draft gauges, etc. 

The kind and location of the various pieces of testing apparatus must be 
left to the judgment of the person conducting the test; always keeping in 
mind the main object, i.e., to obtain authentic data. 

VI. See that the boiler is thoroughly heated before the trial to its usual 
working temperature. If the boiler is new and of a form provided with a 
brick setting, it should be in regular use at least a week before the trial, 
so as to dry and heat the walls. If it has been laid off and become cold, it 
should be worked before the trial until the walls are well heated. 

VII. The boiler and connections should be proved to be free from leaks 
before beginning a test, and all water connections, including blow and extra 
feed pipes, should be disconnected stopped with blank flanges, or bled 
through special openings beyond the valves, except the particular pipe 
through which water is to be fed to the boiler during the trial. During the 
test the blow-off and feed-pipes should remain exposed. 

If an injector is used, it should receive steam directly through a felted 
pipe from the boiler being tested.* 

If the water is metered after it passes the injector, its temperature should 
be taken at the point at which it enters the boiler. If the quantity is deter- 
mined before it goes to the injector, the temperature should be determined 
on the suction side of the injector, and if no change of temperature occurs 
other than that due to the injector, the temperature thus determined is 
properly that of the feed-water. When the temperature changes between 
the injector and the boiler, as by the use of a heater or by radiation, the 
temperature at which the water enters and leaves the injector and that at 
which it enters the boiler should all be taken. The final'temperature cor- 
rected for the heat received from the injector will be the true feed-water 
temperature. Thus if the injector receives water at 50° and delivers it at 
12u° into a heater which raises it to 210°, the corrected temperature is 210 — 
(120 — 50) = 140°. 

See that the steam main is so arranged that water of condensation can- 
not run back into the boiler. 

VIII. Starting and Stopping a Test. — A test should last at least ten hours 
of continuous running, but, if the rate of combustion exceeds 25 pounds of 
coal per square foot of grate per hour it may be stopped when a total of 250 
pounds of coal has been burned per square foot of grate surface. A longer 
test may be made when it is desired to ascertain the effect of widely vary- 
ing conditions, or the performance of a boiler under the working conditions 
of a prolonged run. The conditions of the boiler and furnace in all respects 
should be, as nearly as possible, the same at the end as at the beginning of 
the test. The steam pressure should be the same ; the water level the 

* In feeding a, boiler undergoing test with an injector talcing steam from 
another boiler, or the main steam' pipe from several boilers, the evaporative 
results may be modified by a difference in the quality of the steam from such 
source compared with that supplied by the boiler being tested, and in some 
cases the connection to the injector may act as a drip for the main steam pipe. 
Tfxtis known that the steam' from the main pipe is of the same quality as that 
furnished by the boiler undergoing the test, the steam may be taken from such 
main pipe. 



RULES FOR CONDUCTING BOILER TESTS. 881 



same ; the Are upon the grates should be the same in quantity and condi- 
tion ; and the walls, flues, etc., should be of the same temperature. Two 
methods of obtaining the desired equality of conditions of the tire may be 
used, viz. : those which were called in the Code of 1885 " the standard 
method" and " the alternate method," the latter being employed where it 
is inconvenient to make use of the standard method. 

IX. Standard Method. — Steam being raised to the working pressure, 
remove rapidly all the tire from the grate, close the damper, clean the ash- 
pit, and as quickly as possible start a new tire with weighed wood and coal, 
noting the time and the water level while the water is in a quiescent state, 
just before lighting the tire. 

At the end of the test remove the whole fire, which has been burned low, 
clean the grates and ash-pit, and note the water level when the water is in 
a quiescent state, and record the time of hauling the fire. The water level 
should be as nearly as possible the same as at the beginning of the test. 
If it is not the same, a correction should be made by computation, and not 
by operating the pump after the test is completed. 

X. Alternate Method. — The boiler being thoroughly heated by a prelimi- 
nary run, the fires are to be burned low and well cleaned. Note the amount 
of coal left on the grate as nearly as it can be estimated ; note the pressure 
of steam and tbe water level, and note this time as the time of starting the 
test. Fresh coal which has been weighed should now be fired. The ash- 
pits should be thoroughly cleaned at once after starting. Before the end of 
the test the fires should be burned low, just as before the start, and the 
fires cleaned in such a manner as to leave the bed of coal of the same 
depth, and in the same condition, on the grates, as at the start. The 
water level and steam pressures should previously be brought as nearly as 
possible to the same point as at the start, and tbe time of ending of the test 
should be noted just before fresh coal is fired. If the water level is not the 
same as at the start, a correction should be made by computation, and not 
by operating the pump after the test is completed. 

XI. Uniformity of Conditions. — In all trials made to ascertain maximum 
economy or capacity, the conditions should be maintained uniformly con- 
stant. Arrangements should be made to dispose of the steam so that the 
rate of evaporation may be kept the same from beginning to end. This 
may be accomplished in a single boiler by carrying the steam through a 
waste steam pipe, the discharge from which can be regulated as desired. 
In a battery of boilers, in which only one is tested, the draft can be regu- 
lated on the remaining boilers, leaving the test boiler to work under a con- 
stant rate of production. 

Uniformity of conditions should prevail as to the pressure of steam, the 
height of water, the rate of evaporation, the thickness of fire, the times of 
firing and quantity of coal fired at one time, and as to the intervals between 
the times of cleaning the fires. 

XII. Keeping the Records.— Take note of every event connected with the 
progress of the trial, however unimportant it may appear. Record the 
time of every occurrence and the time of taking every weight and every 
observation. 

The coal should be weighed and delivered to the fireman in equal propor- 
tions, each sufficient for not more than one hour's run, and a fresh portion 
should not be delivered until the previous one has all been fired. The time 
required to consume each portion should be noted, the time being recorded 
at the instant of firing the last of each portion. It is desirable that at the 
same time the amount of water fed into the boiler should be accurately 
noted and recorded, including the height of the water in the boiler, and the 
average pressure of steam and temperature of feed during the time. By 
thus recording the amount of water evaporated by successive portions of 
coal, the test may be divided into several periods if desired, and the degree 
of uniformity of combustion, evaporation, and economv analyzed for each 
period. In addition to these records of the coal and the feed-water, half 
hourly observations should be made of the temperature of the feed-water, 
of the flue gases, of the external air in the boiler-room, of the temperature 
of the furnace when a furnace pyrometer is used, also of the pressure of 
steam, and of the readings of the instruments for determining the moisture 
m the steam. A log should be kept on properly prepared blanks containing 
columns for record of the various observations. 

When the " standard method " of starting and stopping the test is used, 



882 



STEAM. 



the hourly rate of combustion and of evaporation and the horse-power may 
be computed from the records taken during the time when the tires are in 
active condition. This time is somewhat less than the actual time Avhich 
elapses between the beginning and end of the run. This method of 
computation is necessary, owing to the loss of time due to kindling the fire 
at the beginning and burning it out at the end. 

XIII. (Quality of Steam. — The percentage of moisture in the steam should 
be determined by the use of either a throttling or a separating steam calor- 
imeter. The sampling nozzle should be placed in the vertical steam pipe 
rising from the boiler. It should be made of £-inch pipe, and should extend 
across the diameter of the steam pipe to within half an inch of the opposite 
side, being closed at the end and perforated with not less than twenty |-inch 
holes equally distributed along and around its cylindrical surface, but none 
of these holes should be nearer than £ inch to the inner side of the steam 
pipe. The calorimeter and the pipe leading to it should be well covered 
with felting. Whenever the indications of the throttling or separating 
calorimeter show that the percentage of moisture is irregular, or occasion- 
ally in excess of three per cent, the results should be checked by a steam 
separator placed in the steam pipe as close to the boiler as convenient, with 
a calorimeter in the steam pipe just beyond the outlet from the separator. 
The drip from the separator should be caught and weighed, and the per- 
centage of moisture computed therefrom added to that shown by the 
calorimeter. 

Superheating should be determined by means of a thermometer placed in 
a mercury well inserted in the steam pipe. The degree of superheating 
should be taken as the difference between the reading of the thermometer 
for superheated steam and the readings of the same thermometer for satu- 
rated steam at the same pressure as determined by a special experiment, 
and not by reference to steam tables. 

XIV. Sampling the Coal and Determining its Moisture. — As each barrow 
load or fresh portion of coal is taken from the coal pile, a representative 
shovelful is selected from it and placed in a barrel or box in a cool place 
and kept until the end of the trial. The samples are then mixed and 
broken into pieces not exceeding one inch in diameter, and reduced by the 
process of repeated quartering and crushing until a final sample weighing 
about five pounds is obtained, and the size of the larger pieces is such that 
they will pass through a sieve with J-inch meshes. From this sample two 
one-quart, air-tight glass preserving jars, or other air-tight vessels which 
will prevent the escape of moisture from the sample, are to be promptly 
filled, and these samples are to be kept for subsequent determinations of 
moisture and of heating value, and for chemical analyses. During the 
process of quartering, when the sample has been reduced to about 100 
pounds, a quarter to a half of it may be taken for an approximate determi- 
nation of moisture. This may be made by placing it in a shallow iron pan, not 
over three inches deep, carefully weighing it, and setting the pan in the 
hottest place that can be found on the brickwork of the boiler setting or 
flues, keeping it there for at least twelve hours, and then weighing it. 
The determination of moisture thus made is believed to be approximately 
accurate for anthracite and semi-bituminous coals, and also for Pittsburg 
or Youghiogheny coal ; but it cannot be relied upon for coals mined west of 
Pittsburg, or for other coals containing inherent moisture. For these latter 
coals it is important that a more accurate method be adopted. The method 
recommended by the Committee for all accurate tests, whatever the char- 
acter of the coal, is described as follows : 

Take one of the samples contained in the glass jars, and subject it to a 
thorough air-drying in a warm room, weighing it before and after, thereby 
determining the quantity of surface moisture it contains. Then crush the 
whole of it by running it through an ordinary coffee mill, adjusted so as to 
produce somewhat coarse grains (less than J s inch), thoroughly mix the 
crushed sample, select from it a portion of from 10 to 50 grams, weigh it in 
a balance which will easily show a variation as small as 1 part in 1,000, and 
dry it in an air or sand bath at a temperature between 240 and 280 degrees 
Fahr. for one hour. Weigh it and record the loss, then heat and weigh it 
again repeatedly, at intervals of an hour or less, until the minimum weight 
has been reached and the weight begins to increase by oxidation of a por- 
tion of the coal. The difference between the original and the minimum 
weight is taken as the moisture in the air-dried coal. This moisture should 



(*-*) 



RULES FOR CONDUCTING BOILER TESTS. 883 

preferably be made on duplicate samples, and the results should agree 
within 0.3 to 0.4 of one per cent, the mean of the two determinations being 
taken as the correct result. The sum of the percentage of moisture thus 
found and the percentage of surface moisture previously determined is the 
total moisture. 

XV. Treatment of Ashes and Refuse. — The ashes and refuse are to be 
weighed in a dry state. For elaborate trials a sample of the same should 
be procured and analyzed. 

XVI. Calorific Tests and Analysis of Coal. — The quality of the fuel 
should be determined either by heat test or by analysis, or by both. 

The rational method of determining the total heat of combustion is to 
burn the sample of coal in an atmosphere of oxygen gas, the coal to be 
sampled as directed in Article XIV. of this code. 

The chemical analysis of the coal should be made only by an expert 
chemist. The total heat of combustion computed from the results of the 
ultimate analysis may be obtained by the use of Dulong's formula (with 
constants modified by recent determinations), viz. : 14,600 C -f- 62,000 

-f- 4,000 S, in which C, H, O, and S refer to the proportions of 

carbon, hydrogen, oxygen, and sulphur respectively, as determined by the 
ultimate analysis.* 

It is recommended that the analysis and the heat test be each made by 
two independent laboratories, and the mean of the two results, if there is 
any difference, be adopted as the correct figures. 

It is desirable that a proximate analysis should also be made to determine 
the relative proportions of volatile matter and fixed carbon in the coal. 

XVII. Analysis of Flue Gases. — The analysis of the flue gases is an espe- 
cially valuable method of determining the relative value of different meth- 
ods of firing, or of different kinds of furnaces. In making these analyses, 
great care should be taken to procure average samples — since the compo- 
sition is apt to vary at different points of the flue. The composition is also 
apt to vary from minute to minute, and for this reason the drawings of gas 
should last a considerable period of time. Where complete determinations 
are desired, the analyses should be intrusted to an expert chemist. For 
approximate determinations the Orsat or the Hempel apparatus may be 
used by the engineer. 

XVIII. Smoke Observations. — It is desirable to have a uniform system of 
determining and recording the quantity of smoke produced where bitumi- 
nous coal is used. The system commonly employed is to express the degree 
of smokiness by means of percentages dependent upon the judgment of the 
observer. The Committee does not place much value upon a percentage 
method, because it depends so largely upon the personal element, but if 
this method is used, it is desirable that, so far as possible, a definition be 
given in explicit terms as to the basis and method employed in arriving at 
the percentage. 

XIX. Miscellaneous.— In tests for purposes of scientific research, in 
which the determination of all the variables entering into the test is de- 
sired, certain observations should be made which are in general unneces- 
sary for ordinary tests. These are the measurement of the air supply, the 
determination of its contained moisture, the determination of the amount 
of heat lost by radiation, of the amount of infiltration of air through the 
setting, and (by condensation of all the steam made by the boiler) of the 
total heat imparted to the water. 

As these determinations are not likely to be undertaken except by engi- 
neers of high scientific attainments, it is not deemed advisable to give 
directions for making them. 

XX. Calculations of Ejficiency.— Two methods of defining and calculat- 
ing the efficiency of a* boiler are recommended. They are : 

-• TT..O! • .,, , ., Heat absorbed per lb. combustible 

1. Efficiency of the boiler = — — r — -— - • 

Heating value of 1 lb. combustible 

o -cn« • .c x-u *. •! ^ Heat absorbed per lb. coal 

2. Efficiency of the boiler and grate = — — -; = . ,, „ =• 

Heating value of 1 lb. coal 

*Favreand Silberman give 14,544 B.T.U. per pound carbon; Berthelot 
14,647 B.T. U. Favre and Silberman give 62,032 B.T. U. per pound hydro- 
gen; Thomson 61,816 B. T. U. 



884 



STEAM. 



The first of these is sometimes called the efficiency based on combustible, 
and the second the efficiency based on coal. The first is recommended as a 
standard of comparison for all tests, and this is the one which is understood 
to be referred to when the word " efficiency " alone is used without qualifi- 
cation. The second, however, should be included in a report of a test, 
together with the first, whenever the object of the test is to determine the 
efficiency of the boiler and furnace together with the grate (or mechanical 
stoker), or to compare different furnaces, grates, fuels, or methods of firing. 

The heat absorbed per pound of combustible (or per pound coal) is to be 
calculated by multiplying the equivalent evaporation from and at 212° 
per pound combustible (or coal) by 965.7. (Appendix XXI.) 

XXI. The Heat Balance. — An approximate " heat balance," or statement 
of the distribution of the heating value of the coal among the several items 
of heat utilized and heat lost, may be included in the report of a test when 
analyses of the fuel and of the chimney gases have been made. It should 
be reported in the following form : 

Heat Balance, or Distribution of the Heating Value of the Combustible. 
Total Heat Value of 1 lb. of Combustible B. T. U. 



B. T.TJ 



Per 

Cent. 



1. Heat absorbed by the boiler = evaporation from and at 

212° per pound of combustible x 965.7. 

2. Loss due to moisture in coal =: per cent of moisture re- 

ferred to combustible + 100 X [(212 — t) + 966 + 0.48 
(T — 212)] (t = temperature of air in the boiler-room, 
T= that of the flue gases). 

3. Loss due to moisture formed by the burning of hydro- 

gen = per cent of hydrogen to combustible + 100 x 9 

X [(212 — t) + 966 + 0.48 (T - 212)]. 
4.* Loss due to heat carried away in the dry chimney gases 

= weight of gas per pound of combustible x 0.24 X 

(T-t). 

CO 
5.t Loss due to incomplete combustion of carbon: 



~C0 2 +CO 



per cent Cin combustible 
100 



X 10,150. 



6. Loss due to unconsumed hydrogen and hydrocarbons, to 
heating the moisture in the air, to radiation, and un- 
accounted for. (Some of these losses may be sepa- 
rately itemized if data are obtained from which they 
may be calculated.) 

Totals 



100.00 



Dry gas per pound carbon 



which CO n 



* The weight of gas per pound of carbon burned may be calculated from 
the gas analysis as follows : 

_ 11 C0 2 + 8 Q+7 (CO + N) , 
3(C0 2 + CO) 

CO, O, and N are the percentages by volume of the several gases. As the 
sampling and analyses of the gases in the present slate of the art are liable 
to considerable errors, the result of this calculation is usually only an approx- 
imate one. The heat balance itself is also only approximate for this reason, 
as well as for the fact that it is not possible to determine accurately the per- 
centage of unburned hydrogen or hydrocarbons in the flue gases. 

The weight of dry gasper pound of combustible is found by multiplying 
the dry gas per pound of carbon by the percentage of carbon in the combusti- 
ble, and dividing by 100. 

t C0 2 and CO are respectively the percentage by volume of carbonic acid 
and carbonic oxide in the flue gases. The quantity 10,150 = No. heat units 
generated by burning to carbonic acid one pound of carbon contained in car- 
bonic oxide. 



RULES FOR CONDUCTING BOILER TESTS. 885 



XXII. Report of the Trial. — The data and results should be reported in 
the manner given in either one of the two following tables, omitting lines 
where the tests have not been made as elaborately as provided for in such 
tables. Additional lines may be added for data relating to the specific 
object of the test. The extra lines should be classified under the headings 
provided in the tables, and numbered, as per preceding line, with sub let- 
ters, a, b, etc. The Short Form of Report, Table No. 2, is recommended 
for commercial tests and as a convenient form of abridging the longer form 
for publication when saving of space is desirable. 

Table lo. 1. 

Data and Results of Evaporative Test. 

Arranged in accordance with the complete form advised by the Boiler 
Test Committee of the American Society of Mechanical Engineers. 



Made by . of boiler at 

determine 

Principal conditions! governing the trial . . 



Kind of fuel 

Kind of furnace 

State of the weather 

1. Date of trial 

2. Duration of trial hours 

Dimensions and Proportions. 
(A complete description of the boiler should be given on an annexed sheet.) 

3. Grate surface . . . width . . . length . . . area . . sq. ft. 

4. Water-heating surface " 

5. Superheating surface " 

6. Ratio of water-heating surface to grate surface 

7. Ratio of minimum draft area to grate surface 

Average Pressures. 

8. Steam pressure by gauge lbs. 

9. Force of draft between damper and boiler ins. of water 

10. Force of draft in furnace " " 

11. Force of draft or blast in ash-pit " " 

Average Temperatures. 

12. Of external air deg. 

13. Of flreroom " 

14. Of steam " 

15. Of feed-water entering heater ' " 

16. Of feed-water entering economizer " 

17. Of feed-water entering boiler " 

18. Of escaping gases from boiler . . . • 

19. Of escaping gases from economizer 

Fuel. 

20. Size and condition 

21. Weight of wood used in lighting fire lbs. 

22. Weight of coal as fired* " 

* Including equivalent of wood used in lighting the fire, not including un- 
burnt coal withdrawn from furnace at times of cleaning and at end of test. One 



pound of wood is taken to be equal to 0.4 pound of coal , or , in case greater 
accuracy is desired, as having a heat value equivalent to the evapordtic 
6 pounds of water from and at 212° per pound (6 X 965.7 = 5,794 B.T. 



886 STEAM, 



23. Percentage of moisture in coal * ... per cent. 

24. Total weight of dry coal consumed lbs. 

25. Total ash and refuse lbs. 

26. Total combustible consumed 

27. Percentage of ash and refuse in dry coal per cent 

Proximate Analysis of Coal. 

Of Coal. Of Combustible. 

28. Fixed carbon per cent. per cent. 

29. Volatile matter " " 

30. Moisture " 

31. Ash " 



100 per cent 100 per cent. 

32. Sulphur, separately determined " " 

Ultimate Analysis of Dry Coal. 

33. Carbon (C) per cent. 

34. Hydrogen (B) " 

35. Oxygen (O) " 

36. Nitrogen (N) " 

37. Sulphur (S) H 



100 per cent. 

38. Moisture in sample of coal as received " 

Analysis of Ash and Refuse. 

39. Carbon per cent. 

40. Earthy matter ... " 

Fuel per Hour. 

41. Dry coal consumed per hour lbs. 

42. Combustible consumed per hour " 

43. Dry coal per square foot of grate surface per hour ... " 

44. Combustible per square foot of water-heating surface per 

hour " 

Calorific Value of Fuel. 

45. Calorific value by oxygen calorimeter, per lb. of dry coal . B. T. U. 

46. Calorific value by oxygen calorimeter, per lb. of combustible " 

47. Calorific value by analysis, per lb. of dry coalt " 

48. Calorific value by analysis, per lb. of combustible .... " 

Quality of Steam. 

49. Percentage of moisture in steam per cent. 

50. Number of degrees of superheating deg. 

51. Quality of steam (dry steam = unity) 

Water. 

52. Total weight of water fed to boiler J lbs. 

53. Equivalent water fed to boiler from and at 212° .... 

54. Water actually evaporated, corrected for quality of steam 

55. Factor of evaporation § • • 

56. Equivalent water evaporated into dry steam from and at 

212°. (Item 54 -f- Item 55) 

* This is the total moisture in the coal as found by drying it artificially. 
t See formula for calorific value under Article XVI. of Code. 
t Corrected for inequality of water level and of steam pressure at begin- 
ging and end of test. 
§ Factor of evaporation = ~ ' in which IT and h are respectively the 

total heat in steam of the average observed pressure, and in water of the aver- 
age observed temperature of the feed. 



RULES FOR CONDUCTING BOILER TESTS. 887 



Water per Hour 

57. Water evaporated per hour, corrected for quality of steam lbs. 

58. Equivalent evaporation per hour from and at 212° ... . " 

59. Equivalent evaporation per hour from and at 212° per 

square foot of water-heating surface " 

Horse-Power. 

60. Horse-power developed. (34J lbs. of water evaporated per 

hour into dry steam from and at 2 1 2° equals one horse- 
power) * H.P. 

61. Builders' rated horse-power " 

62. Percentage of builders' rated horse-power developed . . . per cent. 

Economic Results. 

63. Water apparently evaporated per lb. of coal under actual 

conditions. (Item 53 -=- Item 22) lbs. 

64. Equivalent evaporation from and at 212° per lb. of coal 

(including moisture). (Item 56 -f- Item 22) " 

65. Equivalent evaporation from and at 212° per lb. of dry 

coal. (Item 56 -^ Item 24) " 

66. Equivalent evaporation from and at 212° per lb. of combus- 

tible. (Item 56 -f Item 26) " 

(If the equivalent evaporation, Items 64, 65, and 66, is 
not corrected for the quality of steam, the fact should 
be stated.) 

Efficiency. 

67. Efficiency of the boiler ; heat absorbed by the boiler per 

lb. of combustible divided by the beat value of one lb. 

of combustible t per cent. 

68. Efficiency of boiler, including the grate ; heat absorbed by 

the boiler, per lb. of dry coal fired, divided by the heat 
value of one lb. of dry coal % 

Cost of Evaporation. 

69. Cost of coal per ton of 2,240 lbs. delivered in boiler room . $ 

70. Cost of fuel for evaporating 1,000 lbs. of water under ob- 

served conditions $ 

71. Cost of fuel used for evaporating 1,000 lbs. of water from 

and at 212° $ 

Smoke Observations. 

72. Percentage of smoke as observed 

73. Weight of soot per hour obtained from smoke meter . . . 

74. Volume of soot obtained from smoke meter per hour . . 

Tal»l«» l^o. 3. 

Data and Results of Evaporative Test. 

Arranged in accordance with the Short Form advised by tbe Boiler Test 
Committee of the American Society of Mechanical Engineers. 

Made by on boiler, at to 

determine 

* Held to be the equivalent of 30 lbs. of water per hour evaporated from 
100° Fahr. into dry steam at 70 lbs. gauge pressure. 

t In all cases where the ivord " combustible " is used, it means the coal with- 
out moisture and ash, but inchiding all other constituents. It is the same as 
what is called in Europe " coal dry and free from ash." 

t The heat value of the coal is to be determined either by av oxygen calorim- 
eter or by calculation from ultimate analysis. When both methods are 
Used the mean value is to be taken. 



STEAM. 



Grate surface ....... - sq.ft. 

Water-heating surface " 

Superheating surface " 

Kind of fuel 

Kind of furnace 

Total Quantities. 

1. Date of trial 

2. Duration of trial hours. 

3. "Weight of coal as fired lbs. 

4. Percentage of moisture in coal per cent. 

5. Total weight of dry coal consumed . lbs. 

6. Total ash and refuse " 

7. Percentage of ash and refuse in dry coal per cent. 

8. Total weight of water fed to the boiler lbs. 

9. Water actually evaporated, corrected for moisture or super- 

heat in steam " 

Hourly Quantities. 

10. Dry coal consumed per hour lbs. 

11. Dry coal per hour per square foot of grate surface ... " 

12. Water fed per hour " 

13. Equivalent water evaporated per hour from and at 212° 

corrected for quality of steam " 

14. Equivalent water evaporated per square foot of water- 

heating hour " 

Average Pressures, Temperatures, etc. 

15. Average boiler pressure . lbs. per sq. iK 

16. Average temperature of feed-water deg. 

17. Average temperature of escaping gases " 

18. Average force of draft between damper and boiler . . . ins. of water 

19. Percentage of moisture in steam, or number of degrees of 

superheating 

Horse-Power. 

20. Horse-power developed (Item 13 -f 34£) H.P. 

21. Builders' rated horse-power " 

22. Percentage of builders' rated horse-power per cent. 

Economic Results. 

23. Water apparently evaporated per pound of coal under 

actual conditions. (Item 8 -f- Item 3) lbs. 

24. Equivalent water actually evaporated from and at 212° per 

pound of coal as fired. (Item 9 -j- Item 3) " 

25. Equivalent evaporation from and at 212° per pound of dry 

coal. (Item 9 -f- Item 5) " 

26. Equivalent evaporation from and at 212° per pound of 

combustible. [Item 9 -£- (Item 5 — Item 6)] " 

(If Items 23, 24, and 25 are not corrected for quality of 
steam, the fact should be stated.) 

Efficiency. 

27. Heating value of the coal per pound B.T. U. 

28. Efficiency of boiler (based on combustible) " 

29. Efficiency of boiler, including grate (based on coal) ... " 

Cost of Evaporation. 

30. Cost of coal per ton of 2,240 pounds delivered in boiler-room $ 

31. Cost of coal required for evaporation of 1,000 pounds of 



water from and at 212° 



DETERMINATION OF MOISTURE. 



889 



DETERMIKATIOKT OF THE MOISTIBE I1Y 
§XEAM. 

The determination of the quality of steam supplied by a boiler is one of 
the most important items in a boiler test. The three conditions to be de- 
termined are : 

a. If the steam is saturated, i.e., contains the quantity of heat due to the 

pressure. 

b. If the steam is wet, i.e., contains less than the amount of heat due to the 

pressure. 

c. If the steam is superheated, i.e., contains more than the amount of heat 

due to the pressure. 

There are several methods of determining the quality of steam ; one being 
to condense all the steam evaporated by a boiler in a surface condenser, and 
weigh the condensing water, taking the temperature at its entrance to and 
exit from the condenser. Another is by use of a barrel calorimeter, in 
which a sample of the steam is condensed directly in a barrel partly filled 
with cold water, the added weight and temperature taken, and by use of a 
formula the quality of steam can be determined. 

Both the above-named methods are now practically obsolete, as their place 
has been taken by the throttling calorimeter, iised for steam in which the 
moisture does not exceed 3 per cent, and the separating calorimeter, for 
steam containing a greater amount of moisture. 

Throttling- Calorimeter. 

In its simplest form this instrument can be made up from pipe fittings, 
the only special parts necessary being the throttling nozzle, which is readily 
made by boring out a piece of brass rod that is the same diameter as a half- 
inch steam pipe, leaving a small hole in one end, say T ^ inch diameter. The 
inside end of the small hole should be tapered with the end of a drill so as 
not to cause eddies ; and the thermometer well, which is a small piece of 
brass pipe, plugged at one end, and fitted into a half-inch brushing to fit 
into place. The following cut hows the instrument as made up from fittings. 
The whole must be carefully covered with some non-conductor, as hair felt. 

THERMOMETER 
WELL 



INSULATING 
MATERIAL 




Fig. 6. 

For more accurate work the instruments designed by George H. Barrus, 
M.E., and Prof. R. C. Carpenter, are to be preferred. Professor Carpenter's 
instrument is shown in the following cut, and differs from the primitive 
instrument previously described only by the addition of the manometer, 



890 



STEAM. 



which determines the pressure of the steam above the atmosphere in the 
body of the calorimeter. With a free exit to the air the pressure in the 
calorimeter may be taken as that of the atmosphere. 

Carpenter's Throttling- Calorimeter. 

(I size. Schaeffer & Budenberg.) 




Fig. 7. 



The perforated pipe for obtaining the sample of steam to be tested should 
preferably be inserted in a vertical pipe, and should reach nearly across 
its diameter. 

Directions for Use. — Connect as shown in the preceding cuts, till 
the thermometer cup with cylinder oil and insert the thermometer. Turn 
on the Globe valve for ten minutes or more in order to bring the tempera- 
ture of the instrument to full heat, after which note the reading of the ther- 
mometer in the calorimeter, and of the attached manometer or of a barometer. 
The steam gauge should be carefully calebrated to see that it is correct. 
A barometer reading taken at the time the calorimeter is in use, gives 
greater accuracy in working up the results than taking the average 
atmospheric pressure as 14.65 pounds. Pressure in pounds may be deter- 
mined from the mercury column of the barometer and manometer by divid- 
ing the inches rise by" 2.03, or taking one pound for each two inches of 
mercury. 

Following is the formula for determining the quality of steam by use of 
the throttling calorimeter. 

H= total heat in a pound of steam at the pressure in the pipe. 
h = total heat in a pound of steam at the pressure in the calorimeter. 
L = latent heat in a pound of steam at the pressure in the pipe. 
t =r temperature in the calorimeter. 

b = temperature of boiling point at calorimeter pressure (taken as 
212° with the " fittings" instrument). 
0.48 = specific heat of superheated steam. 
x = quality of the steam. 
y = percentage of moisture in the steam, 

x = 100 — y. 



DETERMINATION OF MOISTURE. 



891 



If h be taken as 212°, as it can be with but slight error, then 
iT-1146.6-.48(*-212) xl00> 

Following are tables calculated from the above formula. 



JlEoisture in Steam. 

Determinations by Throttling Calorimeter. 





Gauge-pressures. 


s 
^ 


5 


10 


20 


30 


40 


50 


60 


70 


75 


80 


85 90 










Per Cent of Moisture in 


Steam 






0° 


0.51 


0.90 


1.54 


2.06 


2.50 


2.90 


3.24 


3.56 


3.71 


3.86 


3.99 


4.13 


.10° 


0.01 


0.39 


1.02 


1.54 


1.97 


2.36 


2.71 


3.02 


3.17 


3.32 


3.45 


3.58 


20° 






.51 


1.02 


1.45 


1.83 


2.17 


2.48 


2.63 


2.77 


2.90 


3.03 


30° 






.00 


.50 


.92 


1.30 


1.64 


1.94 


2.09 


2.23 


2.35 


2.49 


40° 










.39 


.77 
.24 


1.10 

.57 
.03 


1.40 

.87 
.33 


1.55 

1.01 

.47 


1.69 

1.15 

.60 

.06 


1.80 
1.26 
.72 
.17 


1.94 


m° 










1.40 


60° 












.85 


70° 














.31 




Gauge-pressure. 


r© 


100 


110 


120 


130 


140 


150 


160 


170 


180 


190 


200 


250 










Per Cent of Moisture in 


Steam 






0° 


4.39 


4.63 


4.85 


5. OS 


5.29 


5.49 


5.68 


5.87 


6.05 


6.22 


6.39 


1 
7.16 


10° 


3.84 


4.08 


4.29 


4.52 


4.73 


4.93 


5.12 


5.30 


5.48 


5.65 


5.82 


6.58 


20° 


3.29 


3.52 


3.74 


3.96 


4.17 


4.37 


4.56 


4.74 


4.91 


5.08 


5.25 


6.00 


30° 


2.74 


2.97 


3.18 


3.41 


3.61 


3.80 


3.99 


4.17 


4.34 


4.51 


4.67 


5.41 


40° 


2.19 


2.42 


2.63 


2.85 


3.05 


3.24 


3.43 


3.61 


3.78 


3.94 


4.10 


4.83 


50° 


1.64 


1.87 


2.08 


2.29 


2.49 


2.68 


2.87 


3.04 


3.21 


3.37 


3.53 


4.25 


60° 


1.09 


1.32 


1.52 


1.74 


1.93 


2.12 


2.30 


2.48 


2.64 


2.80 


2.96 


3.67 


70° 


.55 


.77 


.97 


1.18 


1.38 


1.56 


1.74 


1.91 


2.07 


2.23 


2.38 


3.09 


80° 


.00 


.22 


.42 


.63 


.82 


1.00. 


1.18 


1.34 


1.50 


1.66 


1.81 


2.51 


90° 








.07 


.26 


.44 


.61 


.78 


.94 


1.09 


1.24 


1.93 


100° 














.05 


.21 


.37 


.52 


.67 
.10 


1.34 


110° 














.76 



The easiest method of making the determinations from the observations 
is by use of the following diagram, prepared by Professor Carpenter. 

Find in the vertical column at the left the pressure observed in the 
main pipe -4- atmospheric pressure (the absolute pressure), then move hori- 
zontally to the right until over the line giving the degree of superheat 
(t — b), and the quality of steam will be found in a curve corresponding to 
one of those shown, and which may be interpolated where results do not 
come on one of the lines laid down. 



892 

180 
170 
160 
150 



STEAM. 



140 



130 



« 110 



a 100 



90 



70 



60 



50 



40 



20 



10 









1 








j 




/ 




/ 






/ 




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1 












1 






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I 




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1 


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l 








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1 




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i 




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i 




1 


/ 




/ 


l~~ 


i 


1 


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1 




1 




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1 






/ 




/ 






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1 








1 




/ 


/ 




/ 




/ 
/ 




/ 




/ 


/ 


c 


i 




1 




1 






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/ 










/ 


i 


1 


1 




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7 




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1 




/ 




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1 




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/ 


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1 




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10 20 30 40 50 60 70 80 90 

DEGREES OF SUPERHEAT IN THE CALORIMETER 
DIAGRAM GIVING RESULTS FROM THROTTLING CALORIMETER WITHOUT COMPUTATION 

Fig 8. 



DETERMINATION OF MOISTURE. 893 

By putting a valve in the discharge pipe of the calorimeter, being careful 
that when open it offers no obstruction to a free passage of the steam, de- 
terminations may be made from temperatures without reference to a steam 
table, and by using the following diagram by Professor Carpenter no calcu- 
lation is necessary. 

a. Determine the boiling-point of the instrument by opening supplv and 

discharge valves, and showering the instrument with cold water to 
produce moisture in the calorimeter, in which case the boiline-noint 
will be 212° or thereabouts. 

b. Determine temperature due to the boiler pressure by closing the dis- 

charge-valve, leaving the supply-valve open, and obtain the full boiler 
pressure in the calorimeter. 

c. Open the discharge-valve and let the thermometer settle to the tempera- 

ture due to the superheat. 

Deduct the temperature of the boiling-point from this last temperature to 
obtain the degrees superheat. 

Suppose the boiling-point of the calorimeter to be 213°, the following dia- 
gram will give the result directly from the temperatures. 

To use the diagram when the boiling-point differs from 212°, add to the 
temperature of superheat the difference between the true boiling-point and 
212°, if less than 212° ; and subtract the difference if the true boiling-point 
be greater than 212 ; use the result as before. 



Separating- Calorimeter. 

This instrument separates the moisture from the sample of steam, and the 
percentage is then found by the ordinary formula. 

amount of moisture x 100 . , 

= per cent moisture. 



total steam discharged as sample 

One of the most convenient forms of this type of calorimeter is the one 
designed by Professor Carpenter, and shown in Fig. 10. 

The sample of steam is let into the instrument through the angle valve 
6, the moisture gathers in the inner chamber, its weigbt in pounds and 
hundredths being shown on the scale 12, and the dry steam flows out through 
the small calibrated orifice 8. 

By Napier's law the flow of steam through an orifice is proportional to 
the absolute pressure, until the back pressure equals .58 that of the supply. 

The gauge 9 at the right shows in the outer scale the flow of steam 
through the orifice 8 in a period of 10 minutes' time. 

After attaching the instrument to the pipe from which sample is taken 
through a perforated pipe as with the throttling or other instrument, it 
must be thoroughly wrapped with hair, felt, or other insulator. Steam is 
then turned on through the angle valve, and time enough allowed to thor- 
oughly heat the instrument. 

In taking an observation, first observe and record height of water on 
scale 12, then let the steam flow for 10 minutes, observing the average posi- 
tion of the pointer on the flow-gauge ; at the end of 10 minutes observe 
the height of water in gauge 12, and the difference between this and the 
first observation will be the amount of moisture in the sample ; the percent- 
age of moisture will then be found as follows : 

difference in scale 12 X 100 
difference on scale 12 4- average for 10 minutes on the flow-gauge 

— % moisture. 

For tests and data on " Calorimeters," see papers in Trans. A.S.M.E., by 
Messrs G. H. Barrus, A. A. Goubert, and Professors Carpenter, Denton, 
Jacobus, and Peabody. 



894 


220 


230 


STEAM. 

TEMPERATURE IN CALORIMETER 
240 250 260 270 280 290 300 


310 


320 


330 


310 








1 


/ 


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T 






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CURVES OF QUALITY 

FOR USE WITH 
















/ 




/ 


























230 


/ 


/ 


/ 




CARPENT 


ER'S THROTTLING CALC 


RIMETER 




/ 




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220 


/ 




















































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jsio 






















































D 


■z 
AG 


30 

RA 


2 
M 


30 


2- 

?c 


to 

DM 


2 

TE 

PU 


>0 
MP 

fin 


■z 

ER 
G 1 


>o 

AT 

*E£ 


■z 

UR 

UL 
Fi 




E 
T3 


21 
N 

W 


SO 

CA 

Th 


2 
LO 

T 


J0 

ri\ 

4R 


■i 
El 
OT 


H) 

"EF 


3 

NG 


10 


3S 



)RI 


3J 

VIE 



TE 


340 

R. 



determination of moisture. 895 

duality of Steam Shown by Color of Issuing- Jet. 




Fig. 10. Carpenter's New Evaporat- 
ing Calorimeter. (Schaeli'er & Bu- 
denberg.) 



Prof. J. E. Denton (Trans. A. S. 
M. E., vol. x.,p. 349) has demon- 
strated that jets of steam escaping 
from an orifice in a boiler or steam 
reservoir show unmistakable 
change of appearance to the eye 
"when the steam varies less than 
one per cent from the condition of 
saturation either in the direction of 
wetness or superheating. Conse- 
quently if a jet of steam flow from 
a boiler into the atmosphere under 
circumstances such that very lit- 
tle loss of heat occurs through 
radiation, etc., and the jet be 
transparent close to the orifice, or 
be even a grayish white color, 
the steam may be assumed to be 
so nearly dry that no portable 
condensing "calorimeter will be 
capable of measuring the amount 
of water therein. If the jet be 
strongly white, the amount of 
water may be roughly judged up 
to about 2 per cent, but beyond 
this a calorimeter only can deter- 
mine the exact amount of moist- 
ure. With a little experience any 
one may determine by this meth- 
od the conditions of steam within 
the above limits. A common 
brass pet cock may be used as an 
orifice, but it should, if possible, 
be set into the steam drum of the 
boiler and never be placed farther 
away from the latter than four 
feet, and then only when the in- 
termediate reservoir or pipe is 
well covered, for a very short 
travel of dry steam through a 
naked pipe will cause it to become 
perceptibly moist. 

FACTOR! OF EVAPO- 
RATION. 



In order to facilitate the calcu- 
lation of reducing the actual rate 
of evaporation of water from a certain temperature into steam of a cer- 
tain pressure, into the rate from water at 212° F. into steam of 212° a 

table of factors of evaporation is made up from the formula -5^3-=- where 

His the total heat of steam at the observed pressure, and h the total heat 
of feed-water of the observed temperature. 



896 



STEAM. 



Xal»le of factors of Evaporation. 

(Compiled by W. Wallace Christie.) 



Gauge 




















Pressure. 





10 


20 


30 


40 


45 


50 


52 


54 


Temp, of 
Feed. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


212° F. 


1.0003 


1.0088 


1.0149 


1.0197 


1.0237 


1.0254 


1.0271 


1.0277 


1.0283 


209 


1.0035 


1.0120 


1.0180 


1.0228 


1.0268 


1.0286 


1.0302 


1.0309 


1.0315 


206 


1.0066 


1.0151 


1.0212 


1.0260 


1.0299 


1.0317 


1.0334 


1.0340 


1.0346 


203 


1.0098 


1.0183 


1.0243 


1.0291 


1.0331 


1.0349 


1.0365 


1.0372 


1.0378 


200 


1.0129 


1.0214 


1.0275 


1.0323 


1.0362 


1.0380 


1.0397 


1.0403 


1.0409 


197 


1.0160 


1.0246 


1.0306 


1.0354 


1.0394 


1.0412 


1.0428 


1.0434 


1.0441 


194 


1.0192 


1.0277 


1.0338 


1.0385 


1.0425 


1.0443 


1.0460 


1.0466 


1.0472 


191 


1.0223 


1.0308 


1.0369 


1.0417 


1.0457 


1.0474 


1.0491 


1.0497 


1.0503 


188 


1.0255 


1.0340 


1.0400 


1.0448 


1.0488 


1.0506 


1.0522 


1.0528 


1.0535 


185 


1.0286 


1.0371 


1.0432 


1.0480 


1.0519 


1.0537 


1.0554 


1.0560 


1.0566 


182 


1.0317 


1.0403 


1.0463 


1.0511 


1.0551 


1.0568 


1.0585 


1.0591 


1.0598 


179 


1.0349 


1.0434 


1.0495 


1.0542 


1.0582 


1.0600 


1.0616 


1.0623 


1.0629 


176 


1.0380 


1.0465 


1.0526 


1.0574 


1.0613 


1.0631 


1.0648 


1.0654 


1.0660 


173 


1.0411 


1.0497 


1.0557 


1.0605 


1.0645 


1.0663 


1.0679 


1.0685 


1.0692 


170 


1.0443 


1.0528 


1.0589 


1.0636 


1.0676 


1.0694 


1.0710 


1.0717 


1.0723 


167 


1.0474 


1.0559 


1.0620 


1.0668 


1.0707 


1.0725 


1.0742 


1.0748 


1.0754 


164 


1.0505 


1.0591 


1.0651 


1.0699 


1.0739 


1.0756 


1.0773 


1.0780 


1.0786 


161 


1.0537 


1.0622 


1.0682 


1.0730 


1.0770 


1.0788 


1.0804 


1.0811 


1.0817 


158 


1.0568 


1.0653 


1.0714 


1.0762 


1.0801 


1.0819 


1.0836 


2.0842 


1.0848 


155 


1.0599 


1.0684 


1.0745 


1.0793 


1.0833 


1.0850 


1.0867 


1.0873 


1.0880 


152 


1.0631 


1.0716 


1.0776 


1.0824 


1.0864 


1.0S82 


1.0898 


1.0905 


1.0911 


149 


1.0662 


1.0747 


1.0808 


1.0855 


1.0895 


1.0913 


1.0930 


1.0936 


1.0942 


146 


1.0693 


1.0778 


1.0839 


1.0887 


1.0926 


1.0944 


1.0961 


1.0967 


1.0973 


143 


1.0724 


1.0810 


1.0870 


1.0918 


1.0958 


1.0975 


1.0992 


1.0998 


1.1005 


140 


1.0756 


1.0841 


1.0901 


1.0949 


1.0989 


1.1007 


1.1023 


1.1030 


1.1036 


137 


1.0787 


1.0872 


1.0933 


1.0980 


1.1020 


1.1038 


1.1055 


1.1061 


1.1067 


134 


1.0818 


1.0903 


1.0964 


1.1012 


1.1051 


1.1069 


1.1086 


1.1092 


1.1098 


131 


1.0849 


1.0934 


1.0995 


1.1043 


1.1083 


1.1100 


1.1117 


1.1123 


1.1130 


128 


1.0881 


1.0966 


1.1026 


1.1074 


1.1114 


1.1132 


1.1148 


1.1155 


1.1161 


125 


1.0912 


1.0997 


1.1057 


1.1105 


1.1145 


1.1163 


1.1179 


1.1186 


1.1192 


122 


1.0943 


1.1028 


1.1089 


1.1136 


1.1176 


1.1194 


1.1211 


1.1217 


1.1223 


119 


1.0974 


1.1059 


1.1120 


1.1168 


1.1207 


1.1225 


1.1242 


1.1248 


1.1254 


116 


1.1005 


1.1090 


1.1151 


1.1199 


1.1239 


1.1256 


1.1273 


1.1279 


1.1286 


113 


1.1036 


1.1122 


1.1182 


1.1230 


1.1270 


1.1288 


1.1304 


1.1310 


1.1317 


110 


1.1068 


1.1153 


1.1213 


1.1261 


1.1301 


1.1319 


1.1335 


1.1342 


1.1348 


107 


1.1099 


1.1184 


1.1245 


1.1292 


1.1332 


1.1350 


1.1366 


1.1373 


1.1379 


104 


1,1130 


1.1215 


1.1276 


1.1323 


1.1363 


1.1381 


1.1398 


1.1404 


1.1410 


101 


1.1161 


1.1246 


1.1307 


1.1355 


1.1394 


1.1412 


1.1429 


1.1435 


1.1441 


98 


1.1192 


1.1277 


1.1338 


1.1386 


1.1426 


1.1443 


1.1460 


1.1466 


1.1473 


95 


1.1223 


1.1309 


1.1369 


1.1417 


1.1457 


1.1475 


1.1491 


1.1497 


1.1504 


92 


1.1255 


1.1340 


1.1400 


1.1448 


1.1488 


1.1506 


1.1522 


1.1529 


1.1535 


89 


1.1286 


1.1371 


1.1431 


1.1479 


1.1519 


1.1537 


1.1553 


1.1560 


1.1566 


86 


1.1317 


1.1402 


1.1463 


1.1510 


1.1550 


1.1568 


1.1584 


1.1591 


1.1597 


83 


1.1348 


1.1433 


1.1494 


1.1541 


1.1581 


1.1599 


1.1616 


1.1622 


1.1628 


80 


1.1379 


1.1464 


1.1525 


1.1573 


1.1612 


1.1630 


1.1647 


1.1653 


1.1659 


77 


1.1410 


1.1495 


1.1556 


1.1604 


1.1644 


1.1661 


1.1678 


1.1684 


1.1690 


74 


1.1441 


1.1526 


1.1587 


1.1635 


1.1675 


1.1692 


1.1709 


1.1715 


1.1722 


71 


1.1472 


1.1558 


1.1618 


1.1666 


1.1706 


1.1723 


1.1740 


1.1746 


1.1753 


68 


1.1504 


1.1589 


1.1649 


1.1697 


1.1737 


1.1755 


1.1771 


1.1778 


1.1784 


.65 


1.1535 


1.1620 


1.1680 


1.1728 


1.1768 


1.1786 


1.1802 


1.1809 


1.1815 


62 


1.1566 


1.1651 


1.1711 


1.1759 


1.1799 


1.1817 


1.1833 


1.1840 


1.1846 


59 


1.1597 


1.1682 


1.1743 


1.1790 


1.1830 


1.1848 


1.1864 


1.1871 


1.1877 


56 


1.1628 


1.1713 


1.1774 


1.1821 


1.1861 


1.1879 


1.1896 


1.1902 


1.1908 


53 


1.1659 


1.1744 


1.1805 


1.1852 


1.1892 


1.1910 


1.1927 


1.1933 


1.1939 


50 


1.1690 


1.1775 


1.1836 


1.1884 


1.1923 


1.1941 


1.1958 


1.1964 


1.1970 


47 


1.1721 


1.1806 


1.1867 


1.1915 


1.1954 


1.1972 


1.1989 


1.1995 


1.2001 


44 


1.1752 


1.1837 


1.1898 


1.1946 


1.1986 


1.2003 


1.2020 


1.2026 


1.2032 


41 


1.1783 


1.1868 


1.1929 


1.1977 


1.2017 


1.2034 


1.2051 


1.2057 


1.2064 


38 


1.1814 


1.1900 


1.1960 


1.2008 


1.2048 


1.2065 


1.2082 


1.2088 1.2095 


35 


1.1845 


1.1931 


1.1991 


1.2039 


1.2079 


1.2096 


1.2113 


1.2119 1.2126 


32 


1.1876 


1.1962 


1.2022 


1.2070 


1.2110 


1.2128 


1.2144 


1.21511 1.2157 



FACTORS OF EVAPORATION, 



397 



Xa1»le of factors of Evaporation. 



Gauge 


















| 


Pressure. 


56 


58 


60 


65 


70 


75 


80 


85 


90 95 


Temp, of 
Feed. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


212° F. 


1.0290 


1.0295 l.l 


1^0315 


T(J329 


T.0341 


HJ353 


1.0365 


1.0376 


1.0387 


209 


1.0321 


1.0327 


1.0333 


1.0346 


1.0360 


1.0372 


1.0385 


1.0397 


1.0408 


1.0419 


206 


1.0352 


1.0358 


1.0364 


1.0378 


1.0391 


1.0403 


1.C416 


1.0428 


1.0439 


1.0450 


203 


1.0384 


1.0390 


1.0396 


1.0464 


1.0423 


1.0435 


1.0448 


1.0460 


1.0471 


1.0482 


200 


1.0415 


1.0421 


1.0427 


1.0441 


1.0454 


1.0466 


1.0479 


1.0491 


1.0502 


1.0513 


197 


1.0447 


1.0453 


1.0458 


1.0477 


1.0486 


1.0498 


1.0511 


1.0522 


1.0533 


1.0544 


194 


1.0478 


1.0484 


1.0490 


1.0504 


1.0517 


1.0529 


1.0542 


1.0553 


1.0565 


1.0576 


191 


1.0510 


1.0515 


1.0521 


1.0535 


1.0549 


1.0561 


1.0573 


1.0585 


1.0596 


1.0607 


188 


1.0541 


1.0547 


1.0553 


1.0566 


1.0580 


1.0592 


1.0605 


1.0616 


1.0628 


1.0639 


185 


1.0572 


1.0578 


1.0584 


1.0598 


1.0611 


1.0623 


1.0636 


1.0648 


1.0659 


1.0670 


182 


1.0604 


1.0610 


1.0615 


1.0629 


1.0643 


1.0655 


1.0668 


1.0679 


1.0690 


1.0701 


179 


1 .0635 


1.0641 


1.0647 


1.0660 


1.0674 


1.0686 


1.0699 


1.0710 


1.0722 


1.0733 


176 


1.0666 


1.0672 


1.0678 


1.0692 


1.0705 


1.0717 


1.0730 


1.0742 


1.0753 


1.0764 


173 


1.0698 


1.0704 


1.0709 


1.0723 


1.0737 


1.0749 


1.0762 


1.0773 


1.0784 


1.0795 


170 


1.0729 


1.0735 


1.0741 


1.0754 


1.0768 


1.0780 


1.0793 


1.0804 


1.0816 


1.0827 


167 


1.0760 


1.0766 


1.0772 


1.0786 


1.0799 


1.0811 


1.0824 


1.0836 


1.0847 


1.0S58 


164 


1.0792 


1.0798 


1.0803 


1.0817 


1.0831 


1.0843 


1.0856 


1.0S67 


1.0878 


1.0889 


161 


1.0823 


1.0829 


1.0835 


1.0848 


1.0862 


1.0874 


1.0887 


1.0S98 


1.0910 


1.0921 


158 


1.0854 


1.0860 


1.0866 


1.0880 


1.0893 


1.0905 


1.0918 


1.0929 


1.0941 


1.0952 


155 


1.0886 


1.0892 


1.0897 


1.0911 


1.0925 


1.0937 


1.094S 


1.0961 


1.0972 


1.0983 


152 


1.0917 


1.0923 


1.0929 


1.0942 


1.0956 


1.0968 


1.0981 


1.0992 


1.1004 


1.1015 


149 


1.0948 


1.0954 


1.0960 


1.0974 


1.0987 


1.0999 


1.1012 


1.1023 


1.1035 


1.1046 


146 


1.0979 


1.0985 


1.0991 


1.1005 


1.1018 


1.1030 


1.1042 


1.1055 


1.1066 


1.1077 


143 


1.1011 


1.1017 


1.1022 


1.1036 


1.1050 


1.1062 


1.1074 


1.1086 


1.1097 


1.1108 


140 


1.1042 


1.1048 


1.1054 


1.1067 


1.1081 


1.1093 


1.1106 


1.1117 


1.1129 


1.1140 


137 


1.1073 


1.1079 


1.1085 


1.1099 


1.1112 


1.1124 


1.1137 


1.1148 


1.1160 


1.1171 


134 


1.1104 


1.1110 


1.1116 


1.1130 


1.1143 


1.1155 


1.1168 


1.118C 


1.1191 


1.1202 


131 


1.1136 


1.1142 


1.1147 


1.1161 


1.1175 


1.1187 


1.119E 


1.1210 


1.1222 


1.1233 


128 


1.1167 


1.1173 


1.1179 


1.1192 


1.1206 


1.1218 


1.1231 


1.1242 


1.1253 


1.1264 


125 


1.1198 


1.1204 


1.1210 


1.1223 


1.1237 


1.1249 


1.1262 


1.1273 


1.1285 


1.1296 


122 


1.1229 


1.1235 


1.1241 


1.1255 


1.1268 


1.1280 


1.1292 


1.1294 


1.1316 


1.1327 


119 


1.1260 


1.1266 


1.1272 


1.1286 


1.1299 


1.1311 


1.1324 


1.1336 


1.1347 


1.1358 


116 


1.1292 


1.1298 


1.1303 


1.1317 


1.1331 


1.1343 


1.1355 


1.1366 


1.1378 


1.1389 


113 


1.1323 


1.1329 


1.1334 


1.1348 


1.1362 


1.1374 


1.1387 


1.1398 


1.1409 


1.1420 


110 


1.1354 


1.1360 


1.1366 


1.1374 


1.1393 


1.1405 


1.1418 


1.1429 


1.1441 


1.1452 


107 


1.1385 


1.1391 


1 1397 


1.1411 


1.1424 


1.1436 


1.1449 


1.1460 


1.1472 


1.1483 


104 


1.1416 


1.1422 


1.1428 


1.1442 


1.1455 


1.1467 


1.148C 


1.1491 


1.1503 


1.1514 


101 


1.1447 


1.1453 


1.1459 


1.1473 


1.1486 


1.1498 


1.1511 


1.1523 


1.1534 


1 1545 


98 


1.1479 


1.1485 


1.1490 


1.1504 


1.1518 


1.1530 


1.1541 


1.1554 


1.1565 


1.1576 


95 


1.1510 


1.1516 


1.1521 


1.1535 


1.1549 


1.1561 


1.1574 


1.1583 


1.1596 


1.1(07 


92 


1.1541 


1.1547 


1.1553 


1.1566 


1.1580 


1.1592 


1.1605 


1.1616 


1.1628 


1.1639 


89 


1.1572 


1.1578 


1.1584 


1.1598 


1.1611 


1.1623 


1.1636 


1.1647 


1.1659 


1.1670 


86 


1.1603 


1.1609 


1.1615 


1.1629 


1.1642 


1.1654 


1.1667 


1.1678 


1.1690 


1.1701 


83 


1.1634 


1.1640 


1.1646 


1.1660 


1.1673 


1.1685 


1.1698 


1.1709 


1.1721 


1.1732 


80 


1.1665 


1.1671 


1.1677 


1.1691 


1.1704 


1.1716 


1.1729 


1.1741 


1.1752 


1.1763 


77 


1.1696 


1.1702 


1.1708 


1.1722 


1.1735 


1.1747 


1.176C 


1.1772 


1.1783 


1.1794 


74 


1.1728 


1.1734 


1.1739 


1.1753 


1.1767 


1.1779 


1.1791 


1.1803 


1.1814 


1.1825 


71 


1.1759 


1.1765 


1.1770 


1.1784 


1.1798 


1.1810 


1.1823 


1.1834 


1.1845 


1.1856 


68 


1.1790 


1.1796 


1.1802 


1.1815 


1.1829 


1.1841 


1.1854 


1.1865 


1.1877 


1.1888 


65 


1.1821 


1.1827 


1.1833 


1.1846 


1.1860 


1.1872 


1.1885 


1.1896 


1.1908 1.1919 


62 


1.1852 


1.1858 


1.1864 


1.1877 


1.1891 


1.1903 


1.1916 


1.1927 


1.1939 


1.1950 


59 


1.1883 


1.1889 


1.1895 


1.1909 


1.1922 


1.1934 


1.1947 


1.1958 


1.1870 


1.2981 


56 


1.1914 


1.1920 


1.1926 


1.1940 


1.1953 


1.1965 


1.1978 


1.1989 


1.2001 


1.2012 


53 


1.1945 


1.1951 


1.1957 


1.1971 


1.1984 


1.1996 


1.2009 


1.2020 


1.2032 


1.2043 


50 


1.1976 


1.1982 


1.1988 


1.2002 


1.2015 


1.2027 


1.2040 


1.2052 


1.2063 


1.2074 


47 


1.2007 


1.2013 


1.2019 


1.2033 


1.2046 


1.2058 


1.2071 


1.2083 


1.2094 


1.2105 


44 


1.2039 


1.2044 


1.2050 


1.2064 


1.2078 


1.2090 


1.2102 


1.2114 1.2125 


1.2136 


41 


1.2070 


1.2076 


1.2081 


1.2095 


1.2109 


1.2121 


1.2133 


1.2145 


1.2156 


1.2167 


38 


1.2101 


1.2107 


1.2112 


1.2126 


1.2140 


1.2162 


1.2164 


1.2176 


1.2187 


1.2198 


35 


1.2132 


1.2138 


1.2143 


1.2157 


1.2171 


1.21831 1.21961 1.2207 


1.2218 


1.2229 


32 


1.2163 


1.2169 


1.2175 


1.2188 


1.2202 


1.2214| 1.22271 1.2239 


1.2249 


1.2260 



898 



STEAM. 





Xal»Ie of 


Factors of 


Evaporati 


Oil. 






Gauge 




















Pressure. 


100 


105 


115 


125 


135 


145 


155 


165 


185 


Temp, of 
Feed. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


212° F 


1.0397 


1.0407 


1.0427 


1.0445 


1.0462 


1.0478 


1.0493 


1.0509 


1.0536 


209 


1.0129 


1.0438 


1.0458 


1.0476 


1.0493 


1.0509 


1.0524 


1.0540 


1.0567 


206 


1.0460 


1.0470 


1.0489 


1.0510 


1.0527 


1.0543 


1.0558 


1.0574 


1.0601 


203 


1.0492 


1.0502 


1.0521 


1.0540 


10557 


1.0573 


1.0588 


1.0604 


1.0631 


200 


1.0523 


1.0533 


1.0552 


1.0571 


1.0588 


1.0604 


1.0619 


1.0635 


1.0662 


197 


1.0555 


1.0565 


1.0584 


1.0602 


1.0619 


1.0635 


1.0650 


1.0666 


1.0693 


194 


1.0586 


1.0596 


1.0615 


1.0635 


1.0652 


1.0668 


1.0683 


1.0699 


1.0726 


191 


1.0617 


1.0627 


1.0647 


1.0665 


1.0682 


1.0698 


1.0713 


1.0729 


1.0756 


188 


1.0649 


1.0659 


1.0678 


1.0696 


1.0713 


1.0729 


1.0744 


1.0760 


1.0787 


185 


1.0680 


1.0690 


1.0709 


1.0728 


1.0745 


1.0761 


1.0776 


1.0792 


1.0819 


182 


1.0712 


1.0722 


1.0741 


1.0759 


1.0776 


1.0792 


1-0807 


1.0823 


1.0850 


179 


1.0743 


1.0753 


1.0772 


1-0790 


1.0807 


1.0823 


1.0838 


1.0854 


1.0881 


176 


1.0774 


1.0784 


1.0803 


1.0822 


1.0839 


1.0855 


1-0870 


1.0886 


1.0913 


173 


1.0806 


1.0816 


1.0835 


1.0853 


1.0870 


1.0886 


1.0901 


1.0917 


1.0944 


170 


1.0837 


1.0847 


1.0866 


1.0884 


1.0901 


1.0917 


1-0932 


1.0948 


1.0975 


167 


1.0868 


1.0878 


1.0897 


1.0916 


1.0933 


1.0949 


1.0964 


1.0980 


1.1007 


164 


1.0900 


1.0910 


1.0929 


1.0946 


1.0963 


1.0979 


1.0994 


1.1010 


1.1037 


161 


1.0931 


1.0941 


1.0960 


1.0979 


1.0996 


1.1012 


1.1027 


1.1043 


1.1070 


158 


1.0962 


1.0972 


1.0991 


1.1010 


1.1027 


1.1043 


1.1058 


1.1074 1.1101 


155 


1.0993 


1.1003 


1.1023 


1.1041 


1.1058 


1.1074 


1.1089 


1.1105 


1.1132 


152 


1.1025 


1.1035 


1.1054 


1.1073 


1.1090 


1.1107 


1.1122 


1.1138 


1.1165 


149 


1.1056 


1.1066 


1.1085 


1.1103 


1.1120 


1.1136 


1.1151 


1.1167 


1.1194 


146 


1.1087 


1.1097 


1.1116 


1.1135 


1.1152 


1.1168 


1.1183 


1.1199 


1.1226 


143 


1.1118 


1.1129 


1.1148 


1.1166 


1.1183 


1.1199 


1.1214 


1.1230 


1.1257 


140 


1.1150 


1.1160 


1.1179 


1.1197 


1.1214 


1.1230 


1.1245 


1.1261 


1.1288 


137 


1.1181 


1.1191 


1.1210 


1.1228 


1.1245 


1.1262 


1.1277 


1.1293 


1.1320 


134 


1.1212 


1.1292 


1.1241 


1.1260 


1.1277 


1.129.3 


1.1308 


1.1324 


1.1351 


131 


1.1243 


L1253 


1.1273 


1.1291 


1.1308 


1.1324 


1.1339 


1.1355 


1.1382 


128 


1.1275 


1.1285 


1.1304 


1.1322 


1,1339 


1.1355 


1.1370 


1.1386 


1.1413 


125 


1.1306 


1.1316 


1.1335 


1.1353 


1.1370 


1.1386 


1.1401 


1.1417 


1.1444 


122 


1 1337 


1.1347 


1.1366 


1.1384 


1.1401 


1.1417 


1.1438 


1.1448 


1.1475 


119 


1.13S8 


1.1378 


1.1397 


1.1415 


1.1432 


1.1449 


1.1464 


1.1480 


1.1507 


116 


1.1399 


1.1409 


1.1429 


1.1447 


1.1464 


1.1480 


1.1495 


1.1511 


1.1538 


113 


1.1431 


1.1441 


1.1460 


1.1478 


1.1495 


1.1511 


1.1526 


1.1542 


1.1569 


110 


1.1462 


1.1472 


1.1491 


1.1509 


1.1516 


1.1542 


1.1557 


1.1573 


1.1600 


107 


1.1493 


1.1503 


1.1522 


1.1540 


1.1557 


1.1573 


1.1588 


1.1604 


1.1631 


104 


1.1524 


1.1534 


1 .1553 


1.1571 


1.1588 


1.1605 


1.1619 


1.1635 


1.1662 


101 


1.1555 


1.1565 


1.1584 


1.1602 


1.1620 


1.1636 


1.1652 


1.1668 


1.1695 


98 


1.1586 


1.1596 


1.1616 


1.1634 


1.1651 


1.1667 


1.1683 


1.1699 


1.1726 


95 


1.1618 


1.1628 


1.1647 


1.1665 


1.1682 


1.1698 


1.1713 


1.1729 


1.1756 


92 


1.1649 


1.1660 


1.1678 


1.1696 


1.1713 


1.1729 


1.1744 


1.1760 


1.1787 


89 


1.1680 


1.1690 


1.1709 


1.1727 


1.1744 


1.1760 


1.1775 


1.1791 


1.1818 


86 


1.1711 


1.1721 


1.1740 


1.1758 


1.1775 


1.1791 


1.1806 


1.1822 


1.1849 


83 


1.1742 


1.1752 


1.1771 


1.1789 


1.1S06 


1.1823 


1.1837 


1.1853 


1.1880 


80 


1.1773 


1.1783 


1.1802 


1.1820 


1.1837 


1.1854 


1.1869 


1.1885 


1.1912 


77 


1.1804 


1.1814 


1.1834 


1.1852 


1.1869 


1.1885 


1.1900 


1.1916 


1.1943 


74 


1.1835 


1.1845 


1.1865 


1.1883 


1.1900 


1.1916 


1.1932 


1.1948 


1.1975 


71 


1.1867 


1.1877 


1.1896 


1.1914 


1.1931 


1.1947 


1.1961 


1.1977 


1.2004 


68 


1.1898 


1.1908 


1.1927 


1.1945 


1.1962 


1.1978 


1.1993 


1.2009 


1.2036 


65 


1.1929 


1.1939 


1.1958 


1.1976 


1.1993 


1.2009 


1 .2024 


1.2040 


1.2067 


62 


1.1960 


1.1970 


1.19S9 


1.2007 


1.2024 


1.2040 


1.2055 


1.2071 


1.2098 


59 


1.1991 


1.2001 


1.2020 


1.2038 


1.2055 


1.2071 


1.2086 


1.2102 


1.2129 


56 


1.2022 


1.2032 


1.2051 


1.2069 


1.2086 


1.2102 


1.2117 


1.2133 


1.2160 


53 


1.2053 


1.2063 


1.2082 


1.2100 


1.2117 


1.2134 


1.2148 


1.2164 


1.2191 


50 


1.2084 


1.2094 


1.2113 


1.2131 


1.2148 


1.2165 


1.2180 


1.2196 


1.2223 


47 


1.2115 


1.2125 


1.2144 


1.2163 


1.2180 


1.2196 


1.2211 


1.2227 


1 .2254 


44 


1.2146 


1.2156 


1.2176 


1.2194 


1.2211 


1.2227 


1 .2242 


1.2258 


1.2285 


41 


1.2177 


1.2187 


1.2207 


1.2225 


1.2242 


1.2258 


L2273 


1.2289 


1.2316 


38 


1.2208 


1.2219 


1 2238 


1.2256 


1.2273 


1.2289 


1.2304 


1.2320 


1.2347 


35 


1.2240 


1.2250 


12269 


1 2287 


1.2304 


1 2320 


1.2335 


1 .2351 


1.2378 


32 


1.2271 


1.2281 


1.2300 


1.2318 


1.2335 


1.2351 


1.2366 


1.2382 


1.2409 



PROPERTIES OP SATURATED STEAM. 



899 



PROPERTIES aW SATURATED 

(Compiled by W. W. Christie.) 



STEAM. 



Pounds per 
Square Inch. 



304 
1.3 

2.3 
3.3 
4.3 
5.3 

6.3 
7.3 

8.3 
9.3 

10.3 
11.3 
12.3 
13.3 

14.3 
15.3 
16.3 
17.3 

18.3 
19.3 
20.3 
21.3 

22.3 
23 3 
24.3 



26.3 
27.3 






40 



Heat Units in one 
Pound above 32° F. 






102. 
126.2 
141.6 
153.0 

162.3 
170.1 
176.9 
182.9 

188.3 
193.2 
197.7 
201.9 

205.8 
209.5 
213.0 
216.3 

219.4 
222.3 
225.2 

227.9 

230.5 
233.0 
235.4 
237.7 

240.0 
242.1 
244.2 
246.3 

248.3 
250.2 
252.1 
253.9 

255.7 
257.4 
259.1 



262.4 
264.0 
265.6 
267.1 

268.6 
270.0 



■5£ 



70.1 
94.4 
109.8 
121.4 

130.7 
138.5 
145.4 
151.4 

156.9 
161.9 
166.5 
170.7 

174.7 
178.4 
181.9 

185.2 

188.4 
191.4 
194.2 
197.0 

199.6 
202.2 
204.6 
207.0 

209.3 
211.5 
213.6 
215.7 

217.7 

219.7 
221.6 
223.5 

225.3 
227.1 
228.8 
230.5 

232.1 
233.8 
235.3 
236.9 



.21? §3 



1042.9 
1026.0 
1015.2 
1007.2 

1000.7 
995.2 
990.4 



982.4 
978.9 
975.7 
972.8 

970.0 
967.4 
964.9 
962.6 

960.4 
958.3 
956.3 
954.4 

952.5 
950.8 
949.0 
947.4 

945.8 
944.2 
942.7 
941.3 

939.9 
938.9 
937.1 
935.9 

934.6 
933.3 
932.1 
931.0 

929.8 
928.6 
927.5 
926.4 

925.4 
924.3 






1113.0 
1120.4 
1125.1 
1128.6 

1131.4 
1133.8 
1135.8 
1137.7 

1139.3 
1140.8 
1142.2 
1143.5 

1144.7 
1145.8 
1146.9 
1147.9 

1148.8 
1149.7 
1150.6 
1151.4 

1152.2 
1153.0 
1153.7 
1154.4 

1155.1 
1155.8 
1156.4 
1157.0 

1157.6 
1158.2 
1158.8 
1159.3 

1159.9 
1160.4 
1160.9 
1161.5 

1161.9 
1162.4 
1162.9 
1163.4 

1163.8 
1164.3 



Volume. 



Rela- 
tive 



Cu. Ft. 
in 1 Cu. 
Ft. of 
Water. 



20620 
10720 
7326 
5600 

4535 
3814 
3300 
2910 

2607 
2360 
2157 



1846 
1722 
1612 
1514 

1427 

1350.6 
1282.1 
1220.3 

1164.4 
1113.5 
1066.9 
1024.1 

984.8 
948.4 
914.6 
883.2 

854.0 
826.8 
801.2 

777.2 

754.7 
733.5 
713.4 
694.5 

676.6 
659.7 
643.6 

628.2 

613.4 
599.3 



Specific 



Cu. Ft, 

in one 
Lb. of 
Steam. 



319.600 
172.417 
117.723 

89.799 

72.792 
61.311 
53.000 
46.771 

41.858 
37.904 
34.659 
31.932 

29.593 
27.624 

25.858 
24.335 

22.985 
21.781 
20.701 
19.725 

18.839 
18.033 
17.293 
16.615 

15.9S8 
15.409 
14.871 
14.371 

13.904 
13.467 
13.058 
12.674 

12.312 
11.971 
11.649 
11.344 

11.055 
10.756 
10.521 
10.259 

10.037 
9.811 



900 



STEAM. 



PROPEHTIEA OP IATURATED STEAM — Continued. 



Pounds per 
Square Inch. 


CO 
ft CD 

<!£ 


Heat Units in one 
Pound above 32° F. 


Vol 


lime. 


4) O 

8£ 


6 

3 


6 

-2 p 
p 3 


at 






Rela- 
tive 


Specific 


° 2 

^ . 





Cu. Ft. 

in 1 Cu. 

Ft. of 

Water. 


Cu. Ft. 
in one 
Lb. of 
Steam. 




28.3 
29.3 
30.3 
31.3 


43 
44 

45 
46 


271.5 

272.9 
274.3 
275.6 


241.4 

242.8 
244.2 
245.6 


923.3 

922.3 
921.3 
920.3 


1164.7 
1165.1 
1165.6 
1166.0 


586 1 
573.7 
561.8 
550.4 


9.596 
9.391 
9.196 
9.006 


.1064 
.1088 
.1111 
.1134 


32.3 
33.3 
34.3 

35.3 


47 
58 
49 
50 


276.9 

278.2 
279.5 
280.8 


247.0 

248.3 
249.6 
250.9 


919.4 
918.4 
917.5 
916.6 


1166.4 
1166.8 
1167.2 
1167.6 


539.5 
529.0 
518.6 
508.5 


8.826 
8.653 
8.487 
8.326 


.1158 
.1181 
.1204 
.1227 


36.3 
37.3 
38.3 
39.3 


51 
52 
53 
54 


282.1 
283.3 

284.5 
285.7 


252.2 
253.5 
254.7 
255.9 


915.7 
914.8 
913.9 
913.1 


1167.9 
1168.3 
1168.7 
1169.0 


499.1 
490.1 
481.4 
472.9 


8.173 
8.025 
7.882 
7.745 


.1251 

.1274 
.1297 
.1320 


40.3 
41.3 
42.3 
43.3 


55 
56 

57 
58 


286.9 

288.0 
289.1 
290.3 


257.1 

258.3 
259.5 
260.6 


912.2 
911.4 
910.6 
909.8 


1169.4 
1169.7 
1170.1 
1170.4 


464.7 
457.0 
449.6 
442.4 


7.612 
7.484 
7.360 
7.241 


.1343 
.1366 
.1388 
.1411 


44.3 
45.3 
46.3 

47.3 


59 
60 
61 
62 


291.4 

292.5 
293.6 
294.6 


261.7 
262.9 
264.0 
265.1 


909.0 
908.2 
907.4 
906.7 


1170.8 
1171.1 
1171.4 
1171.8 


435.3 

428.5 
422.0 
415.6 


7.125 
7.013 
6.905 
6.800 


.1434 
.1457 
.1479 
.1502 


48.3 
49.3 
50.3 
51.3 


63 
64 
65 
66 


295.7 

296.7 
297.7 
298.7 


266.1 

267.2 
268.3 
269.3 


905.9 
905.2 
904.4 
903.7 


1172.1 
1172.4 
1172.7 
1173.0 


409.4 
403.5 
397.7 
392.1 


6.699 
6.600 
6.505 
6.412 


.1524 
.1547 
.1569 
.1592 


52.3 
53.3 
54.3 

55.3 


67 
68 
69 
70 


299.7 
300.7 
301.7 
302.7 


270.3 
271.3 
272.3 
273.3 


903.0 
902.3 
901.5 
900.9 


1173.3 
1173.6 
1173.9 
1174.2 


386.6 
381.3 
376.1 
371.2 


6.322 
6.234 
6.149 
6.066 


.1614 

.1637 
.1659 
.1681 


56.3 
57.3 
58.3 
59.3 


71 

72 
73 
74 


303.6 
304.6 
305.5 
306.4 


274.3 

275.3 
276.2 

277.2 


900.2 
899.5 
898.8 
898.1 


1174.5 
1174.8 
1175.1 
1175.4 


366.4 
361.7 
357.1 
352.6 


5.986 
5.907 
5.831 
5.757 


.1703 

.1725 
.1748 
.1770 


60.3 
61.3 
62.3 
63.3 


75 
76 

77 
78 


307.3 

308.2 
309.1 
310.0 


278.1 
279.0 
280.0 
280.9 


897.5 
896.8 
896.2 
895.5 


1175.6 
1175.9 
1176.2 
1176.5 


348.3 
344.1 
340.0 
336.0 


5.684 
5.614 
5.546 
5.479 


.1792 
.1814 
•1836 
.1857 


64.3 
65.3 
66.3 
67.3 


79 
80 
81 

82 


310.9 
311.8 
312.6 
313.5 


281.8 

282.7 
283.5 
284.4 


894.9 
894.3 
893.7 
893.1 


1176.7 
1177.0 
1177.3 
1177.5 


332.1 

328.3 
324.6 
320.9 


5.413 

5.342 

5.287 
5.227 


.1879 
.1901 
.1923 
.1945 


68.3 
69.3 


83 

84 


314.3 
315.1 


285.3 
286.1 


892.4 
891.8 


1177.8 
1178.0 


317.3 
313.9 


5.167 
5.110 


.1967 
1988 



PROPERTIES OF SATURATED STEAM. 



901 



PROPERTIES ©E SATTTItATEI» STEAM — Continued. 



Pounds per 
Square Inch. 


. 05 


Heat Units in one 
Pounds above 32° F. 


Volume. 


cpO 

So 


05 

u 

S3 

02 


u 

05 pj 

18 

< 


Mi 


e« 05 eg*| 




Rela- 
tive 


Specific 




II 


Cu. Ft. 
inlCu. 
Ft. of 
Water. 


Cu. Ft. 
n lLb. 

of 
Steam. 


70.3 
71.3 
72.3 
73.3 


85 
86 
87 
88 


316.0 
316.8 
317.6 
318.4 


287.0 

287.8 
288.7 
289.5 


891.2 
890.6 
890.1 
889.5 


1178.3 
1178.5 
1178.8 
1179.0 


310.5 
307.2 
304.0 
300.8 


5.053 
4.998 
4.943 
4.891 


.2010 
.2032 
.2053 
.2075 


74.3 
75.3 
76.3 
77.3 


89 
90 
91 
92 


319.2 
320.0 
320.8 
321.6 


290.3 
291.1 
291.9 
292.7 


888.9 
888.3 
887.8 
887.2 


1179.3 
1179.5 
1179.8 
1180.0 


297.7 
294.7 
291.8 
288.9 


4.839 
4.788 
4.739 
4.690 


.2097 
.2118 
.2139 
.2160 


78.3 
79.3 
80.3 
81.3 


93 
94 
95 
96 


322.3 
323.1 
323.8 
324.6 


293.5 
294.3 
295.1 
295.9 


886.6 
886.1 
885.5 
885.0 


1180.2 
1180.4 
1180.7 
1180.9 


286.1 
283.3 
280.6 
278.0 


4.643 
4.596 
4.551 
4.506 


.2182 
.2204 
.2224 
.2245 


82.3 
83.3 
84.3 
85.3 


97 
98 
99 
100 


325.3 
326.1 
326.8 
327.5 


296.6 

297.4 
298.1 
298.9 


884.5 
883.9 
883.4 
882.9 


1181.1 
1181.4 
1181.6 
1181.8 


275.4 
272.8 
270.3 
267.9 


4.462 
4.419 
4.377 
4.336 


.2266 
.2288 
.2309 
.2330 


86.3 
87.3 
88.3 
89.3 


101 
102 
103 
104 


328.2 
329.0 
329.7 
330.4 


299.6 
300.4 
301.1 
301.8 


882.3 
881.8 
881.3 
880.8 


1182.0 

1182.2 
1182.5 
1182.7 


265.5 
263.2 
260.9 

258.7 


4.296 
4.256 
4.217 
4.179 


.2351 
.2371 
.2392 
.2413 


90.3 
91.3 
92.3 
93.3 


105 
106 
107 
108 


331.1 

331.8 
332.4 
333.1 


302.5 
303.3 
304.0 
304.7 


880.3 
879.8 
879.3 
878.8 


1182.9 
1183.1 
1183.3 
1183.5 


256.5 
254.3 
252.2 
250.1 


4.142 
4.105 
4.069 
4.033 


.2434 
.2454 
.2475 
.2496 


94.3 
95.3 
96.3 
97.3 


109 
110 
111 
112 


333.8 
334.5 
335.1 
335.8 


305.4 
306.1 
306.8 
307.4 


878.3 
877.8 
877.3 
876.9 


1183.7 
1183.9 
1184.1 
1184.3 


248.0 
246.0 
244.0 
242.0 


3.998 
3.964 
3.931 
3.897 


.2516 
.2537 
.2558 
.2578 


98.3 
99.3 
100.3 
1C1.3 


113 
114 
115 
116 


336.5 
337.1 
337.8 
338.4 


308.1 
308.8 
309.5 
310.1 


876.4 

875.9 
875.4 
875.0 


1184.5 
1184.7 
1184.9 
1185.1 


240.1 
238.2 
236.3 
234.5 


3.865 
3.833 
3.802 
3.771 


.2599 
.2619 
.2640 
.2661 


102.3 
103.3 
104.3 
105.3 


117 
118 
119 
120 


339.1 
339.7 
340.3 
340.9 


310.8 
311.4 
312.1 
312.7 


874.5 
874.0 
873.6 
873.1 


1185.3 
1185.5 
1185.7 
1185.9 


232.7 
231.0 
229.3 
227.6 


3.740 
3.711 
3.681 
3.652 


.2681 
.2702 
.2722 
.2742 


106.3 
107.3 
10S.3 
109.3 


121 
122 
123 
124 


341.6 
342.2 
342.8 
343.4 


313.4 
314.0 
314.7 
315.3 


872.7 
872.5 
871-8 
871.3 


1186.1 
1186.3 
1186.5 
1186.6 


226.0 
224.4 
222.8 
221.2 


3.624 
3.596 
3.568 
3.541 


.2762 

.2782 
.2802 
.2822 


110.3 
111.3 


125 
126 


344.0 
344.6 


, 315.9 
316.6 


870.9 
870.4 


1186.8 
1187.0 


219.7 

218.2 


3.515 

3.488 


.2842 
.2862 



M 



902 



STEAM. 



PROPERTIES OF SATURATED STE AJfl — Continued. 



Pounds per 
Square Inch. 



6 


6 






3 


£ 3 


m 


l S 


£»£ 


o£ 


£Ch 


£fr 


O 


< 


112.3 


127 


113.3 


128 


114.3 


129 


115.3 


130 


116.3 


131 


117.3 


132 


118.3 


133 


119.3 


134 


120.3 


135 


121.3 


136 


122.3 


137 


123.3 


138 


124.3 


139 


125.3 


140 


126.3 


141 


127.3 


142 


128.3 


143 


129.3 


144 


130.3 


145 


131.3 


146 


132.3 


147 


133.3 


148 


134.3 


149 


135.3 


150 


136.3 


151 


137.3 


152 


138.3 


153 


139.3 


154 


140.3 


155 


141.3 


156 


142.3 


157 


143.3 


158 


144.3 


159 


145.3 


160 


146.3 


161 


147.3 


162 


148.3 


163 


149.3 


164 


150.3 


165 


151.3 


166 


152.3 


167 


153.3 


168 



S 2 
-^ CO 

si a 
CD u 

PhCL| 

H 



345.2 
345.8 
346.4 
347.0 

347.6 
348.2 
348.8 
349.3 

349.9 
350.5 
351.0 
351.7 

352.2 
352.7 
353.3 
353.8 

354.4 
354.9 
355.5 
356.0 

356.5 
357.1 
357.6 
358.1 

358.6 
359.2 
359.7 
360.2 

360.7 
361.2 
361.7 
362.2 

362.7 
363.2 
363.7 
364.2 

364.7 
365.2 
365.7 
366.2 

366.7 
367.1 



Heat Units in one 
Pound above 32° F. 



AX 



317.2 
317.8 
318.4 
319.0 

319.6 
320.2 
320.8 
321.4 

322.0 
322.6 
323.2 
323.8 

324.3 
324.9 
325.5 
326.1 

326.8 
327.2 
327.8 
328.3 

328.9 
329.4 
330.0 
330.5 

331.1 
331.6 
332.2 
332.7 

333.2 
333.7 
334.3 
334.8 

335.3 
335.8 
336.3 
336.9 

337.4 
337.9 
338.4 
338.9 

339.4 
339.9 






870.0 
869.6 
869.1 
868.7 



867.8 
867.4 
867.0 



865.7 
865.3 

864.9 
864.5 
864.1 
863.7 

863.3 
862.9 
862.5 
862.1 

861.7 
861.4 
861.0 
860.6 



859.8 
859.4 
859.1 

858.7 
858.3 
857.9 
857.6 

857 2 
856.8 
856.5 
856.1 

855.7 
855.4 
855.0 

854.7 

854.3 
853.9 






1187.2 
1187.4 
1187.6 
1187.8 

1187.9 
1188.1 
1188.3 
1188.5 

1188.6 
1188.8 
1189.0 
1189.1 

1189.3 
1189.5 
1189.7 
1189.8 

1190.0 
1190.2 
1190.3 
1190.4 

1190.6 
1190.8 
1191.0 
1191.1 

1191.3 
1191.4 
1191.6 
1191.8 

1191.9 
1192.1 
1192.2 
1192.4 

1192.5 
1192.7 
1192.8 
1193.0 

1193.1 
1193.3 
1193.5 
1193.6 

1193.7 
1193.9 



Volume. 



Rela- 
tive 



Specific 



Cu. Ft. Cu. Ft 

in 1 Cil in 1 Lb 

Ft. of of 

Water. Steam 



216.7 
215.2 
213.7 
212.3 

210.9 
209.5 
208.1 
206.7 

205.4 
204.1 
202.8 
201.5 

200.2 
199.0 
197.8 
196.6 

195.4 
194.2 
193.0 
191.9 

190.8 
189.7 
188.6 
187.5 

186.4 
185.3 
184.3 
183.3 

182.3 
181.3 
1S0.3 
179.3 

178.3 
177.3 
176.4 
175.5 



3.463 
3.437 
3.412 
3.387 

3.363 
3.339 
3.315 
3.292 

3.269 
3.247 
3.224 
3.202 

3.180 
3.159 
3.138 
3.117 

3.097 
3.076 
3.056 
3.037 

3.017 

2.998 
2.980 
2.961 

2.942 
2.924 
2.906 
2.888 

2.871 
2.853 
2.837 
2.819 

2.804 

2.787 
2.770 
2.755 



174.6 2.737 

173.7 | 2.722 

172.8 I 2.706 

171.9 2.691 



171.0 
"170.1 



2.676 
2.661 



CONDENSATION IN STEAM-PIPES. 



903 



PROPERTIES OJF SA1URAIED STEAH — Continued. 



Pounds per 
Square Inch. 


o 

'B'B 

H 


Heat Units in One 
Pound above 32° F. 


Volume. 


v o 
8 -8 


13 
U 

P 
W 


6 

< 


£ ® 

a* 


^ t n J. 


HhWoq 
w 


Rela- 
tive 


Specific 


-1 




Cu. Ft. 
in 1 Cu. 
Ft. of 
Water. 


Cu. Ft. 

in 1 Lb. 

of 

Steam. 


gfgg 

"Sua? 


154.3 
155.3 
156.3 
157.3 


169 
170 
171 
172 


367.6 
368.1 
368.6 
369.1 


340.4 
340.9 
341.4 
341.9 


853.6 
853.2 
852.9 
852.6 


1194.0 
1194.2 
1194 3 
1194.5 


169.2 
168.4 
167.6 
166.8 


2.646 
2.633 
2.617 
2.603 


.3690 
.3709 
.3727 
.3745 


158.3 
159.3 
160.3 
161.3 


173 
174 
175 
176 


369.5 
370.0 
370.5 
370.9 


342.4 
342.8 
343.3 
343.8 


852.2 
851.9 
851.5 
851.2 


1194.6 
1194.8 
1194.9 
1195.0 


166.0 
165.2 
164.4 
163.6 


2.589 
2.575 
2.561 
2.547 


.3763 
.3781 
.3799 
.3817 


162.3 
163.3 
164.3 
165.3 


177 
178 
179 
180 


371.4 
371.9 
372.3 

372.8 


344.3 
344.8 
345.3 
345.7 


850.8 
850.5 
850.2 
849.8 


1195.2 
1195.3 
1195.5 
1195.6 


162.8 
162.0 
161.2 
160.4 


2.533 
2.521 
2.507 
2.494 


.3835 
.3853 
.3871 
.3889 


166.3 
167.3 
168.3 
169.3 


181 
182 
183 
184 


373.2 
373.7 
374.1 
374.6 


346.2 
346.7 
347.1 
347.6 


849.5 
849.2 
848.8 
848.5 


1195.7 
1195.9 
1196.0 
1196.2 


159.7 
159.0 
158.3 
157.6 


2.480 
2.468 
2.455 
2.443 


.3907 
.3925 
.3944 
.3962 


170.3 
171.3 
172.3 
173.3 


185 
186 
187 

188 


375.0 
375.5 
375.9 
376.4 


348.1 
348.6 
349.0 
349.5 


848.2 
847.8 

847.5 
847.2 


1196.3 
1196.4 
1196.6 
1196.7 


156.9 
156.2 
155.5 
154.8 


2.430 
2.418 
2.406 
2.394 


.3980 
.3999 
.4017 
.4035 


174.3 
175.3 
176.3 
177.3 


189 
190 
191 
192 


376.8 
377.2 
377.7 
378.1 


349.9 
350.4 
350.8 
351.3 


846.9 
846.5 
846.2 
845.9 


1196.8 
1197.0 
1197.1 
1197.2 


154.1 
153.4 
152.7 
152.0 


2.382 
2.370 
2.358 
2.347 


.4053 
.4072 
.4089 
.4107 


178.3 
179.3 
180.3 
181.3 


193 
194 
195 
196 


378.5 
379.0 
379.4 
379.9 


351.7 
352.2 
352.6 
353.1 


845.6 
845.3 
845.0 
844.6 


1197.4 
1197.5 
1197.6 
1197.8 


151.3 
150.7 
150.1 
149.5 


2.335 
2.324 
2.312 
2.302 


.4125 
.4143 
.4160 
.4178 


182.3 
183.3 
184.3 
185.3 


197 
198 
199 
200 


380.3 
380.7 
381.1 
381.5 


353.5 
354.0 
354.4 
354.8 


844.3 

844.0 
843.7 
843.4 


1197.9 
1198.0 
1198.1 
1198.3 


148.9 
148.3 
147.7 
147.1 


2.290 
2.279 
2.269 

2.258 


.4196 
.4214 
.4231 
.4249 


186.3 
187.3 
188.3 
189.3 


201 
202 
203 

204 


381.9 
382.4 
382.8 
383.2 


355.3 
355.7 
356.1 
356.6 


843.1 

842.8 
842.5 
842.2 


1198.4 
1198.5 
1198.7 
1198.8 


146.5 
145.9 
145.3 
144.7 


2.248 
2.238 
2.227 
2.216 


.4266 
.4283 
.4300 
.4318 


190.3 
191.3 
192.3 
193.3 


205 
206 
207 
208 


383.6 
384.0 

384.4 
384.8 


357.0 
357.4 
357.9 
358.3 


841.8 
841.5 
841.2 
841.0 


1198.9 
1199.0 
1199.2 
1199.3 


144.1 
143.5 
142.9 
142.3 


2.204 
2.196 
2.186 
2.176 


.4335 
.4352 
.4369 
.4386 


194.3 
195.3 


209 
210 


385.2 
385.6 


358.7 
359.1 


840.7 
840.4 


1199 4 
1199.5 


141.8 
141.3 


2.166 
2.157 


.4403 
.4421 



904 



STEAM. 



CONDENSATION IN ^TEAM-PIPEXi. 

(W. w. c.) 

No very satisfactory figures are found for the absolute condensation 
losses in steam pipes, most of reported tests being compared with hair felt. 

0.012 lbs. per 24 hours per sq. ft. of pipe per degree Fahr., difference in 
temperature of steam and external air, which may be used in calculations, 
is based on the following : 





Sq. ft. 
Sur- 
face. 


Lbs. of Water. 




1 S-i 

§|* 

CD A*® 

a 


a? 

u O 




Test by. 


in 24 
hrs. 


per 
sq. ft. 
in 24 

hrs. 


Covering. 


Bedle & Bauer. 


4130 


11315 


2.74 


262 


.0104 


Asbestos. 


N orris. 


3892 


9360 


2.40 


234 


.0103 


Asbestos. 


Brill. 








308 


.0105 


Magnesia sect'l. 


Norton. 








315 


.0125 


Magnesia. 



The last test by C. L. Norton (Trans. A. £•. M. E., 1898) was made with the 
utmost care. Mr. Norton found that a pipe boxed in with charcoal 1 inch 
minimum thickness was 20 per cent better insulated than when magnesia 
was used, corroborating Mr. Reinhart's statements concerning his experi- 
ence using flue dust to insulate pipes. 

Aboard Ship. — The battleship "Sbikishima" carries 25 Belleville 
boilers capable under full steam of developing 15,000 I.H.P. in the main 
engines besides working the auxiliaries, each boiler supplying steam for 
150 I.H.P. When at anchor, one boiler under easy steam, i.e., evaporating 
from 9 lb. to 10 lbs. of Avater from and at 212° F., per pound of coal — was 
just able to work one 48 K.W. steam dynamo at about half power, together 
with one feed pump, and the air and circulating pumps connected with the 
auxiliary condenser, into which the dynamo engine exhausted, besides 
working a fare and bilge pump occasionally . 

The dynamo was about 160 ft. of pipe length away from the boiler, the 
total range of steam pipe length connected being 500-600 ft. 

Performing the first-mentioned service with only one boiler under steam, 
the coal burned varied from 3£ to 5 tons per day of 18 hours, for about 65 
I.H.P., or about 7 lbs. per indicated horse-power at the best to 10 lbs. at the 
worst, an average of 8 lbs. and over, which shows that more than half the 
fuel must have been expended in keeping the pipes warm. All pipes were 
well covered and below decks, and machinery in first-class condition. 
(London-Engr.) 

Heating- JPipes. — To determine the boiler H.P. necessary for heating, 
it maybe assumed that each sq. ft. of radiating surface will condense about 
0.3 lbs. of steam per hour as a maximum when in active service ; thus 20,000 
sq. ft. times 0.3=6000 lbs. of condensation, which divided by 30 gives 200 
boiler horse-power. 

Condensed steam in which there is no oil may be returned to the boiler 
with the feed-water to be re-evaporated. 



OUTFLOW OF STEAM. 



905 



OUXFIOW OE STEAM: FROIff A GIVEN INITIAL 
PRESSURE lA'TO VARIOUS LOWER PRESSURES. 

(D. K. Clark.) 



Absolute 


Outside 




Velocity of 


Actual Ve- 


Weight Dis- 


Pressure in 


Pressure 


Ratio of 


Outflow at 


locity of 


charged per Sq. 


Boiler per 


per Sq. 


Expansion. 


Constant 


Outflow 


In. of Orifice 


Sq. Inch. 


Inch. 




Density. 


Expanded. 


per Minute 


Lbs. 


Lbs. 


Ratio. 


Ft. per Sec. 


Ft. per Sec. 


Lbs. 


75 


74 


1.012 


227.5 


230 


16.68 


75 


72 


1.037 


386.7 


401 


28.35 


75 


70 


1.063 


490 


521 


35.93 


75 


65 


1.136 


660 


749 


48.38 


75 


61.62 


1.198 


736 


876 


53.97 


75 


60 


1.219 


765 


933 


56.12 


75 


50 


1.434 


873 


1252 


64. 


75 


45 


1.575 


890 


1401 


65.24 


75 


43.46, 58 % 


1.624 


890.6 


1446.5 


65.3 


75 


15 


1.624 


890.6 


1446.5 


65.3 


75 





1.624 


890.6 


1446.5 


65.3 



When, however, steam of varying initial pressure is discharged into the 
atmosphere — pressures of which the atmospheric pressure is not more 
than 58 per cent — the velocity of outflow at constant density, that is, sup- 
posing the initial density to be maintained, is given by the formula — 

V— 3.5953 yh, 
where V =z the velocity of outflow in feet per minute, as for steam of the 
initial density, h = the height in feet of a column of steam of the given 
absolute initial pressure of uniform density, the weight of which is equal to 
the pressure on the unit of base. 

The following table is calculated from this formula : 

OUTFLOW OF STEAM INTO THE ATMOSPHERE. 

(D. K. Clark.) 



Absolute 












Initial 


Outside 


Ratio of 


Velocity of 


Actual Ve- 


Weight Dis- 


Pressure in 


Pressure 


Expansion 


Outflow at 


locity of 


charged per 


Boiler in 


in Lbs. per 


in 


Constant 


Outflow, 


Sq. Inch of 


Lbs. per 


Sq. Inch. 


Nozzle. 


Density. 


Expanded. 


Orifice per Min. 


Sq. Inch. 












Lbs. 


Lbs. 


Ratio. 


Ft. per Sec. 


Ft. per Sec. 


Lbs. 


25.37 


14.7 


1.624 


863 


1401 


22.81 


30 


14.7 


1.624 


867 


1408 


26.84 


40 


14.7 


1.624 


874 


1419 


35.18 


45 


14.7 


1.624 


877 


1424 


39.78 


50 


14.7 


1.624 


880 


1429 


44.06 


60 


14.7 


1.624 


885 


1437 


52.59 


70 


14.7 


1.624 


889 


1444 


61.07 


75 


14.7 


1.624 


891 


1447 


65.30 


90 


14.7 


1.624 


895 


1454 


77.94 


100 


14.7 


1.624 


898 


1459 


86.34 


115 


14.7 


1.624 


902 


1466 


98.76 


135 


14.7 


1.624 


906 


1472 


115.61 


155 


14.7 


1.624 


910 


1478 


132.21 


165 


14.7 


1.624 


912 


1481 


140.46 


215 


14.7 


1.624 


919 


1493 


181.58 



906 



STEAM. 



STEAM PIPES. 

Rankine says the velocity of steam flow in pipes should not exceed 6000 
feet per minute (100 feet per second). As increased size of pipe means in- 
creased loss by radiation, care should be taken that in order to decrease the 
velocity of flow, the losses by radiation do not become considerable. 

The quantity discharged per minute may be approximately found by 
Rankine's formula ("Steam Engine," p. 298), W = 60 ap -^ 70 = 6 ap -f- 7, in 
which W = weight in pounds, a = area of orifice in square inches, and_p = 
absolute pressure. The results must be multiplied by k ■=. 0.93 for a short, 
pipe, and by k = 0.63 for their openings as in a safety valve. 

Where steam flows into a pressure greater than two-thirds the pressure in 
the boiler, W= 1.9 alc^(p — d) d, in which d z=. difference in pressure in 
pounds per square inch between the two sides, and a, p, and £ as above. 
Multiply the results by 2 to reduce to h.p. To determine the necessary dif- 
ference in pressure where a given h.p. is required to flow through a given 
opening, 



HP 2 

14 a 2 k' 



flow of Steam Xhroug-Ii Pipes. 

(G. H. Babcock in " Steam.") 

The approximate weight of any fluid which will flow in a minute through 
any given pipe with a given head or pressure may be found by the formula 



ID (Pi 

' r=87 V~ 



0+t) 



in which W= weight in pounds, d = diameter in inches, Z)=r density or 
weight per cubic foot, p x = initial pressure, p 2 = pressure at the end of the 
pipe, and L = length in feet. 

The following table gives, approximately, the weight of steam per minute 
which will flow from various initial pressures, Avith one pound loss of pres- 
sure through straight smooth pipes, each having a length of 240 times its 
own diameter. For sizes below 6 inches, the flow is calculated from the 
actual areas of " standard " pipe of such nominal diameters. 

For h.p. multiply the figures in the table by two. For any other loss of 
pressure, multiply by the square root of the given loss. For any other 
length of pipe, divide 240 by the given length expressed in diameters, and 
multiply the figures in the table by the square root of this quotient, which 
will give the flow for 1 pound loss of pressure. Conversely dividing the 
given length by 240 will give the loss of pressure for the flow given in the 
table. 

Table of Flow of Steam Through Pipes. 



Initial Pres- 


Diameter of Pipe in Inches. Length of each = 240 Diameters. 


sure by 


























Gauge. 


! 1 l 


1* 


2 


2* 


3 


4 


Lbs. per Sq. 


* i 












Inch. 
















Weight of Steam per Mi 


l. in Lbs 


., with 1 Lb. Loss of Pressure. 


1 


1.16 


2.07 


5.7 


10.27 


15.45 


25.38 


46.85 


10 


1.44 


2.57 


7.1 


12.72 


19.15 


31.45 


58.05 


20 


1.70 


3.02 


8.3 


14.94 


22.49 


36.94 


68.20 


30 


1.91 


3.40 


9.4 


16.84 


25.35 


41.63 


76.84 


40 


2.10 


3.74 


10.3 


18.51 


27.87 


45.77 


84.49 


50 


2.27 


4.04 


11.2 


20.01 


30.13 


49.48 


91.34 


60 


2.43 


4.32 


11.9 


21.38 


32.19 


52.87 


97.60 


70 


2.57 


4.58 


12.6 


22.65 


34.10 


56.00 


103.37 


80 


2.71 


4.82 


13.3 


23.82 


35.87 


58.91 


108.74 


90 


2.83 


5.04 


13.9 


24.92 


37.52 


61.62 


113.74 


100 


2.95 


5.25 


14.5 


25.96 


39.07 


64.18 


118.47 


120 


3.16 


5.63 


15.5 


27.85 


41.93 


68.87 


127.12 


150 


3.45 


6.14 


17.0 


30.37 


45.72 


75.09 


138.61 



STEAM PIPES. 



907 



Table 


of iri©w of 


Steam 


Ttiroug-li Pipes. — Continued. 




Diameter of Pipe in Inches. Length of Eaeh=r 240 Diameters. 


sure by 






















Gauge. 


5 6 


8 


10 


12 


15 18 


Lbs. per Sq. 


1 






1 


1 


Inch. 














Weight of Steam per Min. in Lbs 


., with 1 Lb. Loss of Pressure. 


1 


77.3 


115.9 


211.4 


341.1 


502.4 


804 


1177 


10 


95.8 


143.6 


262.0 


422.7 


622.5 


996 


1458 


20 


112.6 


168.7 


307.8 


496.5 


731.3 


1170 


1713 


30 


126.9 


190.1 


346.8 


559.5 


824.1 


1318 


1930 


40 


139.5 


209.0 


381.3 


615.3 


906.0 


1450 


2122 


50 


150.8 


226.0 


412.2 


665.0 


979.5 


1567 


2294 


60 


161.1 


241.5 


440.5 


710.6 


1046.7 


1675 


2451 


70 


170.7 


255.8 


466.5 


752.7 


1108.5 


1774 


2596 


80 


179.5 


259.0 


490.7 


791.7 


1166.1 


1866 


2731 


90 


187.8 


281.4 


513.3 


828.1 


1219.8 


1951 


2856 


100 


195.6 


293.1 


534.6 


862.6 


1270.1 


2032 


2975 


120 


209.9 


314.5 


573.7 


925.6 


1363.3 


2181 


3193 


150 


228.8 


343.0 


625.5 


1009.2 


1486.5 


2378 


3481 



The loss of head due to getting up the velocity, to the friction of the 
steam entering the pipe and passing elbows and valves, will reduce the 
flow given in the table. The resistance at the opening and that at a 
globe valve are each about the same as that for a length of pipe equal to 

114 diameters divided by a number represented by 1 + -j- • For the sizes of 

pipes given in the table these corresponding lengths are : 



I 



1* I 2 2i 
34 41 47 



3 1 4 
52 60 



71 



12 



The resistance at an elbow is equal to § that of a globe valve. These 
equivalents — for opening, for elbows, and for valves —must be added in 
each instance to the actual length of pipe. Thus a 4-inch pipe, 120 diame- 
ters MO feet) long, with a globe valve and three elbows, would be equivalent 
to 120 -4- 60 -4- 60 4- (3 X 40) = 360 diameters long ; and 360 -f 240 = li. It 
would therefore have 1^ lbs. loss of pressure at the flow given in the table, 
or deliver (1 -f- Vfl — 8.16), 81.6 per cent of the steam with the same (1 lb.) 
loss of pressure. 

Equation of Pipes (Steam). 

It is frequently desirable to know what number of one size of pipes will 
equal in capacity another given pipe for delivery of steam or water. At 
the same velocity of flow two pipes deliver as the squares of their internal 
diameters, but the same head will not produce the same velocity in pipes of 
different sizes or lengths, the difference being usually stated to vary as the 
square root of the fifth power of the diameter. The friction of a fluid 
within itself is very slight, and therefore the main resistance to flow is the 
friction upon the sides of the conduit. This extends to a limited distance, 
and is, of course, greater in proportion to the contents of a small pipe than 

i- a i v5 Se " U majr be a PP rox imated in a given pipe by a constant multi- 
plied by the diameter, or the ratio of flow found bv dividing some power of 
tue diameter by the diameter increased by a constant. Careful compari- 
sons or a large number of experiments, by different investigators, has de- 
V 2 ?P,$ tlae followin ? as a close approximation to the relative flow in pipes 
of different sizes under similar conditions : 

W oo-^^ 
„ ri . V d + 3.6 

W being the weight of fluid delivered in a given time, and d being the 
internal diameter in inches. 



908 



STEAM. 



The diameters of " standard " steam and gas pipe, however, vary from the 
nominal diameters, and in applying this rule it is necessary to take the true 
measurements, which are given in the following table : 

*Tal»le of Standard Sizes Steam and Ga^ Pipes. 





Diameter. 


45 


Diameter. 


ID 


Diameter. 


« 




A 














>q 






£ 


1 


0> 


Inter- 


Exter- 


of 


Inter- 


Exter- 


® 


Inter- 


Exter- 




nal. 


nal. 


N 


nal. 


nal. 


N 


nal. 


nal. 


m 






m 






m 






1 


.27 


.40 


2h 


2.47 


2.87 


9 


8.94 


9.62 


.36 


.54 


3 


3.07 


3.5 


10 


10.02 


10.75 


3 


.49 


.67 


3i 


3.55 


4 


11 


11 


11.75 




.62 


.84 


4 


4.03 


4.5 


12 


12 


12.75 


» 


.82 


1.05 


4i 


4.51 


5 


13 


13.25 


14 




1.05 


1.31 


5 


5.04 


5.56 


14 


14.25 


15 


H 


1.38 


1.66 


6 


6.06 


6.62 


15 


15.43 


16 


u 


1.61 


1.90 


7 


7.02 


7.62 


16 


16.4 


17 


2 


2.07 


2.37 


8 


7.98 


8.62 


17 


17.32 


18 



The following table gives the number of pipes of one size required to 
equal in delivery other larger pipes of the same length and under the same 
conditions. The upper portion above the diagonal line of blanks pertains to 
" standard " steam and gas pipes, while the lower portion is for pipe of the 
actual internal diameters given. The figures given in the table opposite the 
intersection of any two sizes is the number of the smaller-sized pipes 
required to equal one of the larger, 
j 



1 

15- 

14 
13 

12 
11 

10 



I 7 

< 

P 4 



§2 

u. 

° 1 

111 

i 02 



14 



12 



10- 



DIAGRAM GIVING 

DIAMETER OF STEAM AND EXHAUST PIPES 

FOR ENGINE CYLINDERS FROM 5 TO 40 INCHES DIAMETER. 
AT PISTON SPEEDS UP TO 1,000 
FEET PER MINUTE 
FROM " POWER'* 




Fig. 11. 



STEAM PIPES. 



909 



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STEAM PIPES. 



911 



In a paper read before the A. S. M. E. in June, 1898, Prof. C. L. Norton of 
the Massachusetts Institute Technology, gave a series of tables showing the 
results of tests. For the sake of brevity the descriptions of the different 
materials are omitted. The tables follow : 



Specimen. 



Name. 



Loss 
.Ft. 
urfac 
n. 


of 
to 

from 
Pipe. 




B.T.U. 

per Sq 
PipeS 
per M 


G 2 


Ratio 

Loss 
Loss 
Bare 




2.20 


15.9 


1.00 


2.38 


17.2 


.80 


2.38 


17.2 


1.25 


2.45 


17.7 


1.12 


2.49 


18.0 


1.12 


2.62 


18.9 


1.12 


2.77 


20.0 


1.12 


2.80 


20.2 


1.50 


2.87 


20.7 


1.25 


2.88 


20.8 


1.50 


2.91 


21.0 


1.12 


3.00 


21.7 


1.12 


3.33 


24.1 


1.12 


3.61 


26.1 


1.12 


13.84 


100. 





■*-i <d S H 
2° .A | 



Nonpareil Cork Standard 
Nonpareil Cork Octagonal 
Manville High Pressure . 

Magnesia 

Imperial Asbestos . . . 

W. B 

Asbestos Air Cell . . . 
Manville Infusorial Earth 
Manville Low Pressure . 
Manville Magnesia Asbestos 
Magnabestos .... 
Molded Sectional . . 
Asbestos Fire Board . 

Calcite 

Bare Pipe 



Specimen. 



Miscellaneous Substances. 

B.T.U. per 

Specimens. 



sq. ft. per 

min. 

at 200 lbs. 

. 3.18 

. 1.75 

1.90 



Box A, 1 with sand .... 

2 with cork, powdered . . 

3 with cork and infusorial 

earth 

4 with sawdust 2.15 

5 with charcoal 2.00 

6 with ashes 2.46 

Brick wall 4 inches thick . . 5.18 



Pine wood 1 inch thick 
Hair felt 1 inch thick 
Cabot's seaweed quilt 
Spruce 1 inch thick . 
Spruce 2 inches thick 
Spruce 3 inches thick 
Oak 1 inch thick . . 
Hard pine 1 inch thick 



B.T.U. per 

sq. ft. per 

min. 
at 200 lbs. 

. 3.56 

. 2.51 

. 2.78 

. 3.40 
2.31 

. 2.02 

. 3.65 

. 3.72 



Prof. R. C. Carpenter says that there is great difference in the flow of heat 
through a metal plate between different media. In discussing Professor 
Norton's paper he gave the values as shown in the following table as the 
result of experiments conducted in his laboratory. 

Heat Transmitted, in Thermal Units Throug-h Clean Cast- 
iron T»late T 7 g Inch Thick. (Carpenter.) 



Difference 

of 

Temperature. 

Degrees F. 


Steam to Water. 


Lard Oil to Water. 


Air to Water. 


Per Square Foot. 


Per Square Foot. 


Per Square Foot. 


Per Deg 


Total per 


Per Deg. 


Total per 


Per Deg. 


Total per 


per hour 


minute 


per hour 


minute 


per hour 


minute 


B. T. U 


B. T. U. 


B. T. U. 


B. T. U. 


B. T. U. 


B.T.U. 


25 


21 


8.8 


6.5 


2.7 


1.2 


0.5 


50 


48 


40 


13 


10.8 


2.5 


2.7 


75 


84 


110 


19.5 


24.5 


3.7 


5.8 


100 


127 


211 


26 


43.3 


5.0 


8.3 


125 


185 


375 


31.5 


65.5 


6.2 


13 


150 


255 


637 


39 


72.5 


7.5 


18.7 


175 






45.5 


132 


8.7 


25.4 


200 






52 


173 


10 


33 


300 






78 


390 


15 


75 


400 










20 


133 


500 








25 


208 



The above investigation indicates that the substance which surrenders the 
heat is of material importance, as is also the temperature of the surrounding 
media. 



912 



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STANDARD PIPE FLANGES. 



915 



In estimating the effective steam-heating or boiler surface of tubes, the 
surface in contact with air or gases of combustion (whether internal or 
external to the tubes) is to be taken. 

For heating liquids by steam, superheating steam, or transferring heat 
from one liquid or gas to another, the mean surface of the tubes is to be 
taken. 

Collapsing- Pressure in Cylindrical Boiler-flues. 

P = collapsing pressure in pounds per square inch. 
t = thickness of iron plate in inches. 
L = length of tube or flue in feet. 
D= diameter of tube or flue in inches. 

t 2 19 
Then P = 806.300 — W- (Fairbairn.) 



LD 

(kt) 2 
Approximately P =. Vrr in which Jc is a constant = 790 in T 3 g inch plate ; 

800 in J inch ; 810 in T 5 g inch ; 820 in § inch ; 830 in T 7 5 inch ; 840 in \ inch ; 850 
in T 9 H inch ; and 860 in f inch plate. 

§TAIDARD PIPE EXiAWCHSS. 

A. S. M. E. and Master Steam and Hot Water Fitters' Association stan- 
dard, adopted July 18, 1894. Medium pressure includes pressures ranging 
below 75 pounds. High pressure ranges up to 200 pounds per square inch. 





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916 STEAM. 

Notes. — Sizes up to 24 inches are designed for 200 lbs. or less. 

Sizes from 24 to 48 inches are divided into two scales, one for 200 lbs., the 
other for less. 

The sizes of bolts given are for high pressure. For medium pressures the 
diameters are | inch less for pipes 2 to 20 inches diameter inclusive, and i 
inch less for larger sizes, except 48-inch pipe, for which the size of bolt is 12 
inches. 

When two lines of figures occur under one heading, the single columns up 
to 24 inches are for both medium and high pressures. Beginning with 24 
inches, the left-hand columns are for medium and the right-hand lines are 
for high pressures. 

The sudden increase in diameters at 16 inches is due to the possible inser- 
tion of wrought-iron pipe, making with a nearly constant width of gasket a 
greater diameter desirable. 

When wrought-iron pipe is used, if thinner flanges than those given are 
sufficient, it is proposed that bosses be used to bring the bolts up to the 
standard lengths. This avoids the use of a reinforcement around the pipe. 

Figures in the third, fourth, fifth, and last columns refer only to pipe for 
200 lbs. pressure. 

In drilling valve flanges a vertical line parallel to the spindles should be 
midway between two holes on the upper side of the flanges. 



Steam engines are often classed according to the number of cylinders the 
steam passes in succession, and which are different in size, 

Simple expansion, 
Compound, 
Triple, 
Quadruple. 

Any one of the above classes, if run non-condensing, is called low-pres- 
sure, or non-condensing ; and if run with condenser is called high-pressure, 
or condensing. 

Nowadays the above classes are made in two types : high speed, including 
all engines running above, say, 150 revolutions per minute ; and low speed, 
all those running at less than 150 revolutions. 

This division is scarcely correct, as some of the long-stroke engines run- 
ning at 125 revolutions have more than 1000 feet piston speed, while few 
of the so-called high speed machines exceed 600 feet per minute piston 
speed. 

In selecting an engine for electrical work it is necessary" to see that the 
machine is extra heavy in all its parts ; especially so for electric railway 
work, as the changes in load are often great and sudden, and in case of 
short circuit, engines are liable to be called on for tremendous increase in 
output, and should have no weak parts. This especially applies to fly- 
wheels, of which a large number have burst on the large, slow-running 
engines used in railway power-houses. 

Bearings should all be of extra large size, especially so on the main shaft 
journals of large direct-connected units. 

The selection of size (horse-power) depends largely upon the rating of the 
connected electrical machinery and the number of hours it runs, much being 
left to the judgment of the advising engineer. For direct-connected units 
it is not necessary to install an engine of greater rated capacity than the 
rated output of the generator, as the engine will easily care for overload on 
the generator if rated at J cut-off, as is usual. 

Some builders of engines rate their sizes for connections to dynamos so as 
to supply H h. p per k.w. capacity of the dynamo. 

The selection of condensing or high-pressure engines has in the past de- 
pended largely on availability of an adequate supply of water for condens- 
ing purposes ; but to-day the cooling tower with water enough to fill a 
supply-tank once, and a regular supply for boiler-feed, is a very satis- 
factory arrangement. 



STEAM ENGINES. 



91' 



Summary of Tests of Steam Engines of Various Types. 

By Prof. R. C. Carpenter. 



Style of 
Engine. 




=4H CG 

O Ct> 

Ww 


i£ : J 


°W © 

^£w 
» s a 


3 £w" 


Per Cent 
Observed 
H.P. to 
Capacity. 


Boiler 
Evap. per 
lb. Combus. 
B.&A. 212. 


Kind of 
Coal. 


Simple non- 


6 


200 


34.8 


4.47 


110 


55 


11.50 


Pea A. 


condensing 


1 


405 


34.5 


6.54 


257 


63.4 


9.11 


Culm 


slide valve. 


7 


1975 


35.7 


4.60 


862 


51. 


9.46 


Soft Pa. 




11 


300 


37.3 


4.49 


90 


44. 


12.20 


" " 




11 


300 


34.3 


4.72 


95 


46.7 


10.20 


" 111. 




24 


1000 


31.8 


5.38 


717 


71.7 


9.15 


" 




31 


270 


41.5 


5.50 


126 


47.5 


10.60 


Hard, Buck 




33 


270 


31.6 


4.61 


147 


54.5 


10.70 


Pea 


Average. 






35.1 


5.07 




54.2 


10.24 




Simple non- 


17 


300 


30.1 


3.09 


139 


46 


11.45 


Clearfield 


condensing 


19 


150 


26.9 


3.5 


90 


60 


9.73 


Hard, Buck 


Corliss. 


22 


350 


28. 


3.77 


153 


44.7 


8.55 


Soft, Ohio 


Average. 






28.3 


3.45 




50.3 






Compound 


2 


1000 


30.5 


4.22 


603.5 


60.3 


9.03 


1 Soft, 3 Hard 


non-con- 


4 


1250 


36.8 


4.33 


674 


53.8 


9.92 


Culm and slack 


densing. 


21 


400 


34.20 


4.17 


203 


51. 


10.23 


Soft, Pa. 




24 


1200 


30.37 


4.93 


754 


62.7 


9.01 


" 111. 


Average of. 






32.28 


4.55 










Compound 


3a 


600 


29.4 


4.43 


174 


29 


10.38 


1 Soft, 3 hard 


condensing 
high-speed 


3 


600 


23.2 


3.50 


190 


32 


9.93 


" " 


8 


400 


20.2 


3.14 


154 


38 


8.29 


Soft, Ohio 


automatic. 


86 


400 


16.7 


2.40 


180 


45 


7.75 


" " 




13 


250 


24.6 


2.95 


86 


34.5 


10.51 


" Pa. 




16 


350 


22.7 


3.41 


164 


47 


9.50 


Hard pea 




18 


1200 


25.6 


3.61 


904 


75 


10.58 


" " 




21 


400 


29.3 


3.81 


188 


47 


10.23 


Soft 


Average. 






23.96 


3.41 






9.64 




Compound 


10 


825 


22.7 


4.06 


482 


58.2 


8.29 


Culm & Slack 


condensing 


14 


1000 


21.9 


2.56 


277 


27.7 


10.96 


" " 


Corliss, 


14 


L000 


20. 




314 


31.4 


10.96 


" " 


Greene, 


28 


350 


16.64 


2.10 


182 


52.2 


11.80 


Soft 


Mcintosh & 


27 


500 


16.90 


2.61 


290 


58. 


9.36 


" 


Seymour, 


30 


2000 


14.5 


1.80 


814 


40.7 


10.7 


'« 


etc., etc. 


34 


2(10 


17.3 


2.91 


145 


72. 


11.14 


1 




35 


1600 


20.5 


2.18 






11.14 


1 


Average. 






18.8 


2.60 






10.54 





918 



STEAM. 



Horse-power of Steam Engines. 
Hominal Horse-power. — Now very little used. 
D = dia. cyl. in inches. 
A = area of piston in sq. inches. 
L = length of stroke in feet. 

Watt gives, nominal H.P. = ~^r' 

jyi 

Boulton & Watt, nominal H.P. = -— • 

28 

Kent gives as handy rule for estimating the h.p. of a single cylinder engine, 

— . This rule is correct when the product of the m.e.p. and piston speed =r 

21,000. 

The above rule also applies to compound triple and quadruple engines, and 
is referred to the diameter of the low-pressure cylinder, and the h.p. of such 
an engine then becomes 

(dia. low-pres. cyl.) 2 TT „ , . . . 
| ^^ = H.P. (roughly.) 

Indicated Horse Power : I. H.P. — The power developed in 
the cylinder of a steam engine is correctly determined only by use of the 
indicator, and comparisons and steam consumption are always calculated 
on that basis. 
M.E.P. = mean pressure in pounds per square inch, as shown by the 
indicator card. 
L~= stroke of piston in feet. 
n = number of revolutions per min. 
a rz effective area of head side of piston. 
a t = effective area of crank side of piston. 
TTID [(«X m.e.p.) -f- (a, x m.e.p.)] x Ln 
I.H.P._ 33^- 

For multiple cylinder engines, compute I.H.P. for each cylinder, and add 
results together for total power. 

Brake Horse-power. — The brake horse-power (B.H.P.) of an engine 
is the actual or available horse-power at the engine pulley ; at any given 
speed and given brake-load, the B.H.P is less than the corresponding l.H.P. 
by the horse-power required to drive the engine itself at the given speed, 
and with the pressures at the bearings, guides, etc., corresponding to the 
given brake-load. 
If W= load in lbs. on brake lever or rope, 

/= distance in feet of center of Drake-wheel from line of 

action of brake-load, 
A r = revolutions per minute ; 

then B.H.P.=|g. 

The mechanical efficiency of any given engine is less the greater the 
expansion ratio employed, and of two engines of the same type, developing 
the same power at the same speed, that which uses the higher degree of 
expansion will have the lower mechanical efficiency. The effect of this, 
though not usually important, is to make the best ratio of expansion in any 
given case somewhat less than that which makes the steam consumption 
per I.H.P.-hour a minimum. 

The mechanical efficiencies on full load of modern engines range from 80 
to 95 per cent. Large engines have, of course, higher mechanical efficien- 
cies than small ones (a very small engine may have as low a mechanical 
efficiency as 40 to 50 per cent, but this is generally due to bad design and 
insufficient care being taken of the engine), simple than compound engines, 
and compound than triple engines — at any rate when not very large. 

Prof. Thurston estimates that the total mechanical loss in non-condensing 
engines having balanced valves may be apportioned as follows : — main 
bearings 40 to 47 percent, pistons and rods 33 percent, crank-pins 5£ per cent 
slide-valves and rolls 1h per cent, and eccentric straps 5 per cent. An unbal- 
anced slide-valve may absorb 26 per cent, and in a condensing engine the 
air-pump 12 % of the total mechanical loss. 



STEAM ENGINES. 



919 



Cylinder Ratios in Compound JGng-ines. 

The object of building multiple cylinder engines is, 

a, to use high steam pressure, 

b, to get the greatest number of expansions from the steam, 

c, to reduce the cylinder condensation. 

Prof. Thurston says : " Maximum expansion, as nearly adiabatic as prac- 
ticable, is the secret of maximum efficiency." 

Although the theory of determining the sizes of cylinders is perfectly 
understood, yet there are so many causes for varying the results that prac- 
tically to-day but little attention is given to calculations, the plan being to 
use dimensions such as have proved best practice in the past. 

The proportions of cylinders are supposed to be such as to equally divide 
the number of expansions and work among them, and these dimensions 
have to be varied somewhat to meet the experience of the engineer. 

Given the initial pressure (absolute) LP. and the terminal pressure (abso- 

i P 
lute) t.P., then the total number of expansions is E =-j-jj > and the num- 
ber of expansions for each cylinder is as follows : 

Eor compound ^E, 

For triple expansion °^E, 

For quadruple expansion "V E. 

Better results are often obtained by cutting off a trifle earlier in the high- 
pressure cylinder ; and this fact, in connection with the extent of reheaters 
and receivers, changes the actual ratios from the ideal to the practical ones 
shown in the following table : 

Number of Expansions for Condensing- Engines. 





i.P. 

Abso- 
lute. 


Total 
Expan- 
sions. 


Expansions in Each Cylinder. 


Type. 


1st. 


2d. 


3d. 


4th. 


Single cylinder .... 

Compound 

Triple compound . . . 
Quadruple compound 


65 
145 
185 

265 


7 
22 
30 
48 


7. 

4.8 

3.2 

2.7 


4.6 
3.1 
2.65 


3.0 

2.6 


2.55 



For triple engines, Jay M. Whitham* recommends the following relative 
sizes of cylinders when the piston-speed is from 750 to 1,000 ft. per minute : 



Boiler Pressure 

(above 
Atmosphere). 


High-Pressure 
Cylinder. 


Intermediate 
Cylinder. 


Low-Press ure 
Cylinder. 


130 
140 
150 
160 


1 

1 
1 
1 


2.25 
2.40 
2.55 
2.70 


5.00 
5.85 
6.90 

7.25 



The following are the maximum, average, and minimum values of the 
relative cylinder volumes of triple-expansion condensing engines, working 
with boiler pressures of 150 or 160 lbs. per square inch above atmosphere, on 
board 65 boats launched within the last three or four years : — 





High-Pressure 
Cylinder. 


Intermediate 
Cylinder. 


Low-Pressure 




Cylinder. 


Maximum value 
Average " 
Minimum " 


1 
1 

1 


2.84 
2.58 
1.89 


7.56 
6.71 
4.59 



American Society of Mechanical Engineers, 1889. 



920 



STEAM. 



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co t- 

CS OS 



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s a 



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3 a 



§ fl 



s & a 8 £ 



CO CO CO 

00 00 CO 



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10 io ia o 









lO lH CO i-l 



os ia i-H 
00 cs o 

LO LO CO 



CO CO CO 



lO OS 

8 8 



COCOOOtFOiOOLOOLO 
COt— t-OOCSOSCOOi-li-l 
LO LO LO lO LO lO CO CO CO CO 



S 8 



<N <M i-t 



i-l CN CO -# 






I ^H 



<N <M — I 



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>X» I *? 



"P o 3 



§ 3 



3 § 



S S3 



.as 



lO 

CO CO 

I «. 



2 a 



OS CO t- 

3 3 3 



"fcoS 



8 S 






2 8 8 






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^ s 



CO CO CO CO 



3 9 



-aoaBJ^o^Q- 



STEAM ENGINES. 921 

Receiver Capacity. — In compound engines with cranks at right 
angles the receiver capacity should be from 1 to 1.5 times that of the 
high-pressure cylinder (Seaton), or not less than the capacity of the low- 
pressure cylinder ("Practical Engineer"). When the cranks are oppo- 
site, the receiver capacity need not exceed that of the steam passage from 
the high-pressure to the low-pressure cylinder. The general effect of large 
receiver capacity is to cause a drop between the pressure at the end of the 
high-pressure expansion stroke and the beginning of the high-pressure ex- 
haust stroke and low-pressure admissioD, thus increasing the power devel- 
oped in the high-pressure, and decreasing the power developed in the low- 
pressure cylinder ; this leads to a loss of power in the engine, and one 
which — at any rate in engines Avith cranks at right angles — is greater the 
more the receiver capacity exceeds that necessary for free passage of the 
steam. 

Steam JPorts and Passag-es. — The areas of these should be such 
that the mean linear velocity of the steam does not exceed 5,000 to 6,000 feet 
per minute ; hence, if 

D = diameter of cylinder in inches, 

A = area of cylinder in square inches, 

a = area of port or passage in square inches, 

S = piston-speed in feet per minute ; 

° ~ 6,000 "~ 7,640 
for mean velocity of steam 6,000 feet per minute ; 
_ AS _ D 2 S 
a ~ 5,000 "~ 6,370 
for mean velocity of steam 5,000 feet per minute. 

The lengths of the steam passages between the cylinders and valves 
should be as small as possible, in order to minimize clearance and resist- 
ance to flow of steam. 

Condensers and Pumps. 

Condensers are principally of two types, viz., Jet Condensers, in which 
the steam and condensing water mix in a common vessel, from which both 
are pumped by the air-pump ; and Surface Condensers, in which the steam 
generally passes into a chamber containing a number of brass tubes, through 
which the condensing water is made to circulate. The latter form is usually 
adopted where water is bad, as it enables the same feed- water to be passed 
through the boiler over and over again. 

The capacity of a jet condenser should not be less than one-fourth of the 
low-pressure cylinder, but need not exceed one-half, unless the engines are 
very quick running ; one-third is a good average ratio. Large condensers 
require more time for forming the vacuum, while small condensers are 
liable to flood and overflow back to the cylinders. The amount of condens- 
ing water required per pound of steam condensed varies with the tempera- 
ture of the exhaust, of the " hot-well," and of the condensing water. (The 
"hot-well "is the receptacle into which the air-pump delivers the water 
from the condenser.) The feed-water is obtained from the "hot-well," 
which should be maintained at 110° to 120° F. Sometimes even 130° F. can be 
obtained with care. 

The amount of cooling or tube surface depends upon the difference be- 
tween the temperature of the exhaust steam and the average temperature 
of tbe cooling water, and on the thermal conductivity and thickness of the 
metal tubes. For copper and brass tubes in good condition the rate of 
transmission is about 1,000 units (equivalent to about 1 lb. of steam con- 
densed) per square foot per 1° F. difference of temperature per hour. With 
the hot-well at 110° and the cooling water at 60°, the average difference is 
25°, and 25 lbs. of steam should be condensed per hour per square foot. In 
practice allowance must be made for the working conditions of the tubes, 
and half the above, i.e., Jib. of steam per 1°F. difference is nearer the usual 
allowance ; and under the above conditions about 12.5 lbs. of steam would be 
condensed per square foot per hour, which is considered very fair work. 

The tubes are generally of brass, No. 18 S.W.G. thick, and from J to 1 in. 
diameter, according to the length of the tubes ; they are usually f in. in 



922 



STEAM. 



diameter, and spaced at a pitch of 1^ in., w:iile the tube-plates, which are 
also of brass, are 1£ to 1£ in. thick for § in tubes. The length of the tubes, 
when unsupported between plates, should not exceed 120 diameters. 
If H=z total heat of 1 lb. of exhaust steam in B. T.U., 
t = temperature F.° of hot-well, 
t x = temperature F.° of cooling water on entering, 
t 2 =. temperature F.° of cooling Abater on leaving, 

(X = quantity in lbs. of cooling water per lb. of steam for jet condenser, 
Q. z = ditto for surface condenser ; 

& = --, 



<?2 = 



H—t 



for jet condenser, 



h — h 

t = k— q. 2 



_ (to — t t ), for surface condensers. 
N.B. H—t =1, 050 approximately. 
Values of Q Y and Q<, for different temperatures of cooling water, when H— 
1150, t = 110, and U = 100 in case of Q, : — 









Values of t x 








40 


50 


60 


70 


80 


&...,". 


15 


17 


21 


26 


35 


Q 2 . . . . 


17 


21 


26 


35 


52 



Area of injection orifice should be such as to allow a velocity of flow of 
water not exceeding 1,500 feet per minute. It is better to have a large ori- 
fice and to control the flow of water by an injection valve. 

Area of orifice in square inches. 

— lbs. water per minute ~ 650 to 750. 
= area of piston -f- 250. 

The cooling or circulating water in surface condensers should travel some 
20 ft. lineally through the tubes. In small condensers, Avhere this is not 
convenient, and the water only circulates twice through short tubes, the 
rate of flow must be reduced. 

A replenishing cock should be fitted to allow of the passage of part of the 
circulating water into the air-pump suction to provide for water lost in 
drains, blowing off, leakage, etc. This may have one-tenth the area of the 
feed-pipe. 

A cock should be fitted close to the exhaust inlet for introducing caustic- 
soda when required to dissolve grease off the tubes. 

Assume your engine to require 20 pounds of steam per horse-power per 
hour, or one-third of a pound per minute, and to exhaust at atmospheric 
pressure. One pound of steam at atmospheric pressure contains 1146.1 heat 
units above 32°. One pound of water at this temperature contains approxi- 
mately 120 — 32 =r 88 heat units above 32°, so that to change a pound oi steam 
at atmospheric pressure into water at 120°, we should have to take from it 
1146.1 — 88 = 1058.1 heat units, and for one-third of a pound, 1058.1 -f- 3= 
352.7 heat units. Suppose the injection water to be 60°. In heating to PiO^ 
each pound will absorb approximately 60 heat units, so that it would take 
352.7 -£- 60 = 5.88 pounds of injection water per minute per horse-power 
under' the assumed conditions. A higher terminal pressure, higher tem- 
perature of injection, less efficiency in the engine, or lower hot-well 
temperature, will increase this figure. 

In order to cover all conditions, makers and dealers figure that a con- 
denser should be able to supply from a gallon to a gallon and a half of in- 



STEAM ENGINES. 923 



jection water per minute for each indicated horse-power developed. The 
capacity of a single-acting vertical air-pump should, be from one-tenth to 
one-twelfth that of the cylinder ; of a double-acting horizontal pump, from 
one-sixteenth to one-nineteenth. 

Ejector Condensers are made on the principle of steam injectors except 
that the action is reversed, the cooling water taking the place of the steam 
in the injector, and the exhaust steam that of the feed-water. In order to 
ensure their successful working, the cooling water should be supplied at a 
head of 15 feet to 25 feet, either from a tank above or from a centrifugal or 
other pump. The amount of cooling water required is about the same as for 
jet condensing ; the vacuum is from 20 in. to 25 in. 

Air-pumps are used to draw the condensed water from the condenser to 
the hot-well, together with the air originally contained in the water, or 
Avhich may find its way in through glands, etc., and with jet condensers 
they also draw the cooling water. A cubic foot of ordinary water contains 
about .05 cubic foot of air at atmospheric pressure, which expands in the 
condenser to about .4 cubic foot of air ; hence the term air-pump. 

The efficiency of a single-acting air-pump may be taken at .6 to .4, and 
generally .5, while that of the double-acting pump may be .5 to .3, say .4 on 
average. For jet condensing, the volume of the air-pump should be theo- 
retically 1.4 times the volume of condensed + cooling water; for good 
working it should be from twice to thrice that required by theory. Or if 
v ■= volume of condensed Abater per minute in cubic feet, 
V=z volume of cooling water per minute in cubic feet, 
n = number of strokes (useful) of air-pump per minute, 
A = volume of air-pump in cubic feet ; 

v -4- V 
A = 2.8 — ' for single-acting pumps, 

v 4- V 
= 3.5 — - — for double-acting pumps. 

Since, for surface condensing, the air-pump does not draw the cooling 
water, and as the feed-water, being used over again, should not contain so 
much air, it would appear that the air-pump might be much smaller 
thru for jet condensing. However, surface condensers are frequently 
arranged for use as jet condensers in case of mishap, and with surface con- 
densing a better vacuum is expected, so that for surface condensing the air- 
pump is only slightly less than for jet condensing. In actual practice the 
air-pump is made from one-tenth to one-twenty-fifth the capacity of 
the low-pressure cylinder, according to the number of expansions and 
nature of condenser, while a comparison of a number of marine engines by 
different makers shows a ratio of one-sixteenth to one twenty-first. 

If expansion joints are used in the exhaust pipe, a copper bellows joint is 
better than the ordinary gland and stuffing-box type, through which air is 
apt to leak. 

Air-pump valves should have sufficient area that the full quantity of cool- 
ing and condensed water in jet condensation in passing does not exceed a 
velocity of 400 feet per minute ; in practice the area is larger than this. A 
large number of small valves is perhaps better than one or two large valves 
which are sluggish, owing to their inertia. The clearance space between 
head and foot valves should not exceed one-fifteenth the capacity of the 
pump as ordinarily constructed. 

If a = area through foot valves in square inches, 
a f = area through head valves in square inches, 
a = diameter of discharge pipe in inches, 
D = diameter of the air-pump in inches, 
S = speed (useful) in feet per minute ; 

If there be no air vessel or receiver, d should be 10 per cent larger. 



924 



STEAM. 



An air-pipe should be fitted to the hot-well one-fourth the diameter of 
the discharge pipe. 

Circulating* Pumps. — The size of these depend chiefly on conditions 
mentioned for air-pumps, and they may bear a constant relation to the air- 
pump as to size, or to the L.P. cylinders. 

Air-pump. Circulating Pump. Ratio. 
Single acting Single acting .6 

Single acting Double acting .31 

Double acting Double acting .52 

or if V— volume of cooling water in cubic feet per minute, 
S = length of stroke in feet, 
n = number of strokes (useful) per minute, 
C=. capacity of pump in cubic feet, 
D = diameter of pump in inches ; 

n 

D — 13.55 J~ 
T nS 

Circulating pump valves should be of sufficient area that the mean velo- 
city of flow does not exceed 3 or 4 feet per sec. High velocities tend to 
wear out the valves, and cause undue resistance in the pump. In the suc- 
tion and delivery pipes the velocity should not exceed 500 feet per minute, 
or for large and easy leads 600 feet per minute. Better results, however, 
will be obtained by using larger pipes, so as to reduce the velocity, espe- 
cially if the pipes are long. For single-acting pumps the suction may be 
smaller than the delivery, if the pump be below the water-level. 
If a = minimum area through valves in square inches, 
d = minimum diameter of pipe in inches, 
A — area of pump in square inches, 
D = diameter of pump in inches, 
S rr mean speed (useful) of pump in feet per minute ; 

AS 
a = l80' 

where Ovaries from 22 for small pumps to 25 for large pumps, while for the 
suction of single-acting pumps it may be 27. 

Air chambers should always be fitted, which for single-acting pumps may 
be twice the capacity of the pump. An air-pipe should be fitted to the 
highest points of the water passages for escape of air to enable the con- 
denser and pipes to run full. If the speed of the circulating pump cannot 
be varied independently, it is advisable to fit a water valve between the two 
ends of the pump, so that the discharge may be varied to suit the require- 
ments. 

Strainers should be fitted to the inlet of the suction pipe, and the aggre- 
gate area of the passages should be from two to four times the area of the 
pipe, according to the velocity of flow in the pipe. Owing to difficulty ex- 
perienced in cleaning strainers when under water, they are sometimes fixed 
in a cast-iron vessel near the suction entrances to the pump, with a door 
arranged in some convenient position for cleaning. 

Foot Valve. — When the water level is below that of the pump, a foot 
valve should be fitted just above the surface of the water. A door should 
be provided for examining the valve without disturbing the suction pip$. 
Or an air ejector may be used to charge the pump. 



STEAM ENGINES. 



925 



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wheel or pulley diameter in feet 
Fig. 12 



926 WATER-POWER. 



WATER-POWER. 

IN determining the feasibility of utilizing water-power to operate electri 
cally the industries of any particular town or city, careful consideration 
must be given to the following points, viz. : 1. The amount of water-power 
permanently available. 2. The cost of developing this power. 3. The in- 
terest on this amount. 4. The total demand for power. 5. The amounts 
and relative locations of the various kinds of power. 6. The cost of steam 
plants now in operation. 7. The interest on this amount. 8. Cost of fuel 
for plants now in operation. 9. Cost of operating present plants. Labor. 
10. Cost of maintenance of present plants. 11. The amounts and kinds of 
electric power already in operation. 12. The distance of transmission. 
13. The estimated cost of the hydraulic machinery. 14. The guaranteed 
efficiency and regulation of the hydraulic machinery- 15. Estimated cost of 
electric machinery. 16. Estimated cost of line construction. 17. Total cost 
of operating hydraulic and electric machinery. 18. Total cost of mainte- 
nance of hydraulic and electric plants. 19. The interest on the total esti- 
mated cost of proposed plant. 20. The estimated gross income. 

Charles T. Main makes the following general statements as to the value 
of a water-power : " The value of an undeveloped variable power is usually 
nothing if its variation is great, unless it is to be supplemented by a steam- 
plant. It is of value then only when the cost per horse-power for the double- 
plant is less than the cost of steam-power under the same conditions as 
mentioned for a permanent power, and its value can be represented in the 
same manner as the value of a permanent power has been represented. 

" The value of a developed power is as follows : If the power can be run 
cheaper than steam, the value is that of the power, plus the coat of plant, 
less depreciation. If it cannot be run as cheaply as steam, considering its 
cost, etc., the value of the power itself is nothing, but the value of the plant 
is such as could be paid for it new, which would bring the total cost of run- 
ning down to the cost of steam-power, less depreciation." 

Mr. Samuel Webber, Iron Age, Feb. and March, 1893, criticises the state- 
ments of Mr. Main and others who have made comparisons of costs of steam 
and of water-power unfavorable to the latter. He says : " They have based 
their calculations on the cost of steam, on large compound engines of 1000 
or more h. p. and 120 pounds pressure of steam in their boilers, and by care- 
ful 10-hour trials succeeded in figuring down steam to a cost of about $20 
per h. p., ignoring the well-known fact that its average cost in practical use, 
except near the coal mines, is from $40 to $50. In many instances dams, 
canals, and modern turbines can be all completed at a cost of $100 per h. p.; 
and the interest on that, and the cost of attendance and oil, will bring 
water-power up to but about $10 or $12 per annum ; and with a man compe- 
tent to attend the dynamo in attendance, it can probably be safely estimated 
at not over $15 per h. p. 

SYIVOPSIS OF REPORT REdHIRED OJT 

WATER-POWER PROPER1Y, 

location. 

Geographical, etc. 
Sketch of river and its tributaries. 
Surrounding country and physical features. 
Sources ; lakes, springs, etc. 
Water's head ; area drained, nature of ; whether forest, swamp, snow- 
covered mountains, etc. 
Elevation of head Avaters and of mouth. 
Length from main source to mouth. 
Accessibility ; how and by what routes. 

Reports. 

Reports of U. S. Coast or Geological Survey. 

Reports of Engineers U. S. Army. 

Any other reports. 

Any estimate by engineers and for what purpose. 

When it first attracted attention and for what reason. 

History. 



REPORT ON WATER-POWER PROPERTY. 927 

Rainfall. 

Average for several years for the drainage area. Maximum, what month. 
Minimum, what month. Comparison with other similar localities. 

Volume of Water. 

Gauging of river if possible. Reports by other engineers. 
Cubic feet per second flow. 

Cubic feet per second per mile of watershed = say .2 to .3 of total rainfall 
and | available as water-poAver. 
Comparison Avith other rivers. 

Reservoirs. 

Possibility of storing water for dry time. 

Available Fall. 

Location of ; accessibility, by Avhat routes. 

Can power be used locally, or Avould it be necessary to transmit it, and if 
so, where to, and distances ? Nature of country over which it would have to 
be carried. 

Volume of water in cubic feet per second. 

Horse-Power of River. 

Calculated from available fall and volume. 

Horse-poAver for each fall or dam. 

Location of dams, dimensions, length, and height, best method of con- 
struction, estimated cost. 

Backwater ; volume, andhoAV far ; what interests disturbed by it ; benefits, 
if any. 

Compare power with that of similar rivers. 

Probable cost of power at dams and transmitted. 

Applications Possible. 

Near by ; at distance, stating when and for what. Note industries appli- 
cable to ; comparison with other applications. 

lew Industries Sugg-ested, 

and old industries already going to which poAver is applicable. 

Cost to these, and comparison Avtth cost of other forms of power already 
in use. 

Property of tlie Company. 

Land, buildings, water rights, flowage rights, franchises, lines, rights of 
way. Character of deeds. Probable value. 

Comparison AA'ith other similar properties. 

Other resources. 

liabilities. 

Stocks, bonds, floating debt, other. 

Earning: Capacity. 

Probable cost of power per h. p. at power-house. 

Probable cost of power per h. p. delivered or transmitted. 

Price for which it can be sold at power-house, and price transmitted or 
delivered. 

Gfeneral features. 

Surrounding country, its characteristics, people, cities, and towns, indus- 
tries, condition of finances. 

Facilities for transportation, water and rail. 

Nearness of sources of supplies and sales of products. 

Horse-Power of a "Waterfall. 

The horse-poAver of a waterfall is expressed in the following formula : 

Q = quantity of Avater in cubic feet floAving over the fall in 1 minute. 

H=. total head in feet, i.e., the distance betAveen the surface of the water at 

the top of the fall, and that at its foot. In a water-power the head is 

the distance between the surface of the water in the head-race, and that 

of the Avater in the tail-race. ^ 



928 WATER POWER. 



w = weight of water per cubic foot = 62.36 lbs. at 60° F. 

Gross horse-power of waterfall = ., OAnn or .00189 QH. 

ooOOO 

Loss of bead at the entrance to and exit from a water-wheel, together with 
the friction of the water passing through, reduces the power that can be 
developed to about 70 per cent of the gross power of the fall. 

Horse-Power of a Running' Stream. 

The power is calculated by the same formula as for a fall, but in this case 
H=. theoretical head due to the velocity of the water in the stream = 
v 2 . 
6^4 Whei ' e 
v = velocity of water in feet per second. 

Q = the cubic feet of water actually impinging against the bucket per 
minute. 

Gross borse-power = .00189 QH. 
Wheels for use in the current of a stream realize only about .4 of the gross 
theoretical power. 

Current motors are often developed to operate in strong currents, such as 
that of the Niagara River opposite Buffalo, but are of little use excepting 
for small powers. Such a small fraction of the current velocity can be 
made use of that a current motor is extremely inefficient. In order to 
realize power from a current it is necessary to reduce its velocity in taking 
the power, and to get the full power would necessitate the backing up of the 
whole stream until the actual head equaled the theoretical. 

Power of Water flowing* in a Pipe. 

v 2 v 2 

Hdue to velocity =r — = — - where v = velocity in feet per second. 

f 
H x due to pressure = — , where /r= pressure in lbs. per square foot. 

and w — 62.36 lbs. = weight 1 cubic foot of water. 
H 2 distance above datum line in feet. 

Total H— t- +-+H 2 . 

In hydraulic transmission the work or energy of a given quantity of water 
under pressure is the volume in cubic feet x lbs. pressure per square foot. 
Q = cubic feet per second. 
P = pressure in lbs. per square inch. 

Horse-power = ^^p = -2618 PQ. 

Mill-Power. 

It has been customary in the past to lease water-power in units larger 
than the horse-power, and the term mill-power has been used to designate 
the unit. The term has no uniform value, but is different in all localities. 

Emerson gives the following values for the seven more important water- 
power. 

Holyoke, Mass. — Each mill-power at the respective falls is declared to have 
the right during 16 hours in a day to draw 38 cubic feet of water per second 
at the upper fall when the head there is 20 feet, or a quantity proportionate 
to the height at the falls. This is equal to 86.2 horse-power as a maximum. 

Lowell, Mass. — The right to draw during 15 hours in the day so much 
water as shall give a power equal to 25 cubic feet a second at the great fall, 
when the fall there is 30 feet. Equal to 85 h. p. maximum. 

Lawrence, Mass. — The right to draw during 16 hours in a day so much 
water as shall give a horse-power equal to 30 cubic feet per second when the 
head is 25 feet. Equal to 85 h. p. maximum. 

Minneapolis, Minn. — 30 cubic feet of water per second with head of 22 
feet. Equal to 74.8 h. p. 



COMPARISON OF COLUMNS. 



929 



Manchester, N. IT. —Divide 725 by the number of feet of fall minus 1, and 
the quotient will be the number of cubic feet per second in that fall. For 20 
feet fall this equals 38.1 cubic feet, equal to 86.4 h. p. maximum. 

Cohoes, N.Y. — "Mill-power" equivalent to the power given by G cubic 
feet per second, when the fall is 20 feet. Equal to 13.6 h. p. maximum. 

Passaic, N. J. — Mill-power : The right to draw 8^ cubic feet of water per 
second, fall of 22 feet, equal to 21.2 horse-power. Maximum rental, .§700 per 
year for each mill-power = §33.00 per h. p. 

The horse-power maximum above given is that due theoretically to the 
weight of water and the height of the fall, assuming the water-wheel to have 
perfect efficiency. It should be multiplied by the efficiency of the wheel, 
say 75 per cent for good turbines, to obtain the h.p. delivered by the wheel. 

At Niagara power has in all cases been sold by the horse-power delivered 
to the wheels if of water, and to the building-line if electrical. 

Charges for water in Manchester, Lowell, and Lawrence, are as follows : 

Jiff/ IXcIlSStST* 

About $300 per year per mill-power for original purchases. 
$2 per day per mill-power for surplus. 

Lowell. 
About $300 per year per mill-power for original purchases. 
$2 per day per mill-power during " back-water." 
$4 per day per mill-power for surplus under 40 per cent. 

$10 per day per mill-power for surplus over 40 per cent and under 50 per cent. 
$20 per day per mill-power for surplus over 50 per cent. 
$75 per day per mill-power for any excess over limitation. 

Laivrence. 
About $300 per year per mill-power for original purchases. 
About $1200 per year per mill-power for new leases at present. 
$4 per day per mill-power fur surplus up to 20 per cent. 
$8 per day per mill-power for surplus over 20 and under 50 per cent. 
$4 per day per mill-power for surplus under 50 per cent. 



COSIPAMSOIV Off COLUMNS Off 
Jttercury in Inches, antl Pressure in 1 



WATEB T1X 

il»s., per ftquai 



FEE1, 
e Inch. 



Lbs. 


Water. 


Merc'ry 


Water. 


Merc'ry 


Lbs. 


Merc'ry 


Water. 


Lbs. 


Press. 










Press. 






Press. 


Sq. In. 


Feet. 


Inches. 


Feet. 


Inches. 


Sq. In. 


Inches. 


Feet. 


Sq. In. 


1 


2.311 


2.046 


1 


0.8853 


0.4327 


1 


1.1295 


0.4887 


2 


4.622 


4.092 


2 


1.7706 


0.8654 


2 


2.2590 


0.9775 


3 


6.933 


6.138 


3 


2.6560 


1.2981 


3 


3.3885 


1.4662 


4 


9.244 


8.184 


4 


3.5413 


1.7308 


4 


4,5181 


1.9550 


5 


11.555 


10.230 


5 


4.4266 


2.1635 


5 


5.6476 


2.4437 


6 


13.866 


12.2276 


6 


5.3120 


2.5962 


6 


6.7771 


2.9325 


7 


16.177 


14.322 


7 


6.1973 


3.0289 


7 


7.9066 


3.4212 


8 


18.488 


16.368 


8 


7.0826 


3.4616 


8 


9.0361 


3.9100 


9 


20.800 


18.414 


9 


7.9680 


3.8942 


9 


10.165 


4.3987 


10 


23.111 


20.462 


10 


8.8533 


4.3273 


10 


11.295 


4.8875 


11 


25.422 


22.508 


11 


9.7386 


4.7600 


11 


12.424 


5.3762 


12 


27.733 


24.554 


12 


10.624 


5.1927 


12 


13.554 


5.8650 


13 


30.044 


26.600 


13 


11.509 


5.6255 


13 


14.683 


6.3537 


14 


32.355 


28.646 


14 


12.394 


6.0582 


14 


15.813 


6.8425 


15 


34.666 


30.692 


15 


13.280 


6.4909 


15 


16.942 


7.3312 


16 


36.977 


32.738 


16 


14.165 


6.9236 


16 


18.072 


7.8200 


17 


39.288 


34.784 


17 


15.050 


7.3563 


17 


19.201 


8.3087 


18 


41.599 


36.830 


18 


15.936 


7.7890 


18 


20.331 


8.7975 


19 


43.910 


3S.876 


19 


16.821 


S.2217 


19 


21.460 


9.2862 


20 


46.221 


40.922 


20 


17.706 


8.6544 


20 


22.590 


9.7750 


21 


48.532 


42.968 


21 


18.591 


9.0871 


21 


23.719 


10.264 


22 


50.843 


45.014 


22 


19.477 


9.5198 


22 


24,849 


10.752 


23 


53.154 


47.060 


23 


20.362 


9.9525 


23 


25.978 


11.241 


24 


55.465 


49.106 


24 


21.247 


10.385 


24 


27.108 


11.7300 


25 


57.776 


51.152 


25 


22.133 


10.818 


25 


28.237 


12.219 


26 


60.087 


53.198 


26 


23.018 


11.251 


26 


29.367 


12.707 


27 


62.39S 


55.244 


27 


23.903 


11.683 


27 


30.496 


13.196 


28 


64.70E) 


57.290 


28 


24.789 


12 116 


28 


31.626 


13.685 


39 


67.020 


59.336 


29 


25.674 


12.549 


29 


32.755 


14.174 


30 


69.331 


61.386 


1 30 


26.560 


12.981 


30 


33.885 


14.662 



930 



WATER-POWER. 



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. per Yea 
per M. P. 

Cost of P 
cost, and 




o^S 


O^ 




wwlssS 




©53 s© 


?pa 




^O,- 


* „ 




2 s 9 

2 5 c 


Sip 

75 a 




age 


©-*> 




SpO 


Xh 




oo 33 


fe-S 




g ClO CD © 










eV oh^ 






'1 



PRESSURE UF WATER. 



931 



PRESSURE OF WATER. 

The pressure of water in pounds per square inch for every foot in height 
to 300 feet ; and then by intervals to 1000 feet head. 



Feet 


Press., 


Feet 


Press., 


Feet 


Press., 


Feet 


Press., 


Feet 


Press., 


He'd. 


Sq. In. 


He'd. 


Sq. In. 


He'd. 


Sq. In. 


Head. 


Sq. In. 


Head. 


Sq. In. 


1 


0.43 


65 


28.15 


129 


55.88 


193 


83.60 


257 


111.32 


2 


0.86 


66 


28.58 


130 


56.31 


194 


84.03 


258 


111.76 


3 


1.30 


67 


29.02 


131 


50.74 


195 


84.47 


259 


112.19 


4 


1.73 


68 


29.45 


132 


57.18 


196 


84.90 


260 


112.62 


5 


2.16 


69 


29.88 


133 


57.61 


197 


85.33 


261 


113.06 


6 


2.59 


70 


30.32 


134 


58.04 


198 


85.76 


262 


113.49 


7 


3.03 


71 


30.75 


135 


58.48 


199 


86.20 


263 


113.92 


8 


3.46 


72 


31.18 


136 


58.91 


200 


86.63 


264 


114.36 


9 


3.89 


73 


31.62 


137 


59.34 


201 


87.07 


265 


114.79 


10 


4.33 


74 


32.05 


138 


59.77 


202 


87.50 


266 


115.22 


11 


4.76 


75 


32.48 


139 


60.21 


203 


87.93 


267 


115.66 


12 


5.20 


76 


32.92 


140 


60.64 


204 


88.36 


268 


116.09 


13 


5.63 


77 


33.35 


141 


61.07 


. 205 


88.80 


269 


116.52 


14 


6.06 


78 


33.78 


142 


61.51 


206 


89.23 


270 


116.96 


15 


6.49 


79 


34.21 


143 


61.94 


207 


89.66 


271 


117.39 


16 


6.93 


80 


34.65 


144 


62.37 


208 


90.10 


272 


117.82 


17 


7.36 


81 


35.08 


145 


62.81 


209 


90.53 


273 


118.26 


18 


7.79 


82 


35.52 


146 


63.24 


210 


90.96 


274 


118.69 


19 


8.22 


83 


35.95 


147 


63.67 


211 


91.39 


275 


119.12 


20 


8.66 


84 


36.39 


148 


64.10 


212 


91.83 


276 


119.56 


21 


9.09 


85 


36.82 


149 


64.54 


213 


92.26 


277 


119.99 


22 


9.53 


86 


37.25 


150 


64.97 


214 


92.69 


278 


120.42 


23 


9.96 


87 


37.68 


151 


65.40 


215 


93.13 


279 


120.85 


24 


10.39 


88 


38.12 


152 


65.84 


216 


93.56 


2S0 


121.29 


25 


10.82 


89 


38.55 


153 


66.27 


217 


93.99 


281 


121.72 


26 


11.26 


90 


38.98 


154 


66.70 


218 


94.43 


282 


122.15 


27 


11.69 


91 


39.42 


155 


67.14 


219 


94.86 


283 


122.59 


28 


12.12 


92 


39.85 


156 


67.57 


220 


95.30 


284 


123.02 


29 


12.55 


93 


40.28 


157 


68.00 


221 


95.73 


285 


123.45 


30 


12.99 


94 


40.72 


158 


68.43 


222 


96.16 


286 


123.89 


31 


13.42 


95 


41.15 


159 


68.87 


223 


96.60 


287 


124.32 


32 


13.86 


96 


41.58 


160 


69.31 


224 


97.03 


288 


124.75 


33 


14.29 


97 


42.01 


161 


69.74 


225 


97.46 


289 


125.18 


34 


14.72 


98 


42.45 


162 


70.17 


226 


97.90 


290 


125.62 


35 


15.16 


99 


42.88 


163 


70.61 


227 


98.33 


291 


126.05 


36 


15.59 


100 


43.31 


164 


71.04 


228 


98.76 


292 


126.48 


37 


16.02 


101 


43.75 


165 


71.47 


229 


99.20 


293 


126.92 


38 


16.45 


102 


44.18 


166 


71.91 


230 


99.63 


294 


127.35 


39 


16.89 


103 


44.61 


167 


72.34 


231 


100.06 


295 


127.78 


40 


17.32 


104 


45.05 


168 


72.77 


232 


100.49 


296 


128.22 


41 


17.75 


105 


45.48 


169 


73.20 


233 


100.93 


297 


128.65 


42 


18.19 


106 


45.91 


170 


73.64 


234 


101.36 


298 


129.08 


43 


18.62 


107 


46.34 


171 


74.07 


235 


101.79 


299 


129.51 


44 


19.05 


108 


46.78 


172 


74.50 


236 


102.23 


300 


129.95 


45 


19.49 


109 


47.21 


173 


74.94 


237 


102.66 


310 


134.28 


46 


19.92 


110 


47.64 


174 


75.37 


238 


103.09 


320 


138.62 


47 


20.35 


111 


48.98 


175 


75.80 


239 


103.53 


330 


142.95 


48 


20.79 


112 


48.51 


176 


76.23 


240 


103.90 


340 


147.28 


49 


21.22 


113 


48.94 


177 


76.67 


241 


104.39 


350 


151.61 


50 


21.65 


114 


49.38 


178 


77.10 


242 


104.83 


360 


155.94 


51 


22.09 


115 


49.81 


179 


77.53 


243 


105.26 


370 


160.27 


52 


22.52 


116 


50.24 


180 


77.97 


244 


105.69 


380 


164.61 


53 


22.95 


117 


50.68 


181 


78.40 


245 


106.13 


390 


168.94 


54 


23.39 


118 


51.11 


182 


78.84 


246 


106.56 


400 


173.27 


55 


23.82 


119 


51.54 


183 


79.27 


247 


106.99 


500 


216.58 


56 


24.26 


120 


51.98 


184 


79.70 


248 


107.43 


600 


259.90 


57 


24.69 


121 


52.41 


185 


80.14 


249 


107.86 


700 


303.22 


58 


25.12 


122 


52.84 


186 


80.57 


250 


108.29 


800 


346.54 


59 


25.55 


123 


53.28 


187 


81.00 


251 


108.73 


900 


389.86 


60 


25.99 


124 


53.71 


188 


81.43 


252 


109.16 


1000 


433.18 


61 


26.42 


125 


54.15 


189 


81.87 


253 


109.59 






62 


26.85 


126 


54.58 


190 


82.30 


254 


110.03 






63 


27.29 


127 


55.01 


191 


82.73 


255 


110.46 






64 


27.72 


12S 


55.44 


192 


83.17 


256 


110.89 







932 WATER-POWER. 



RITETED STEEL PIPES, 

Riveted sheet steel pipe is much used on the Pacific Coast for conveying 
water for considerable distances under high heads, say as much as 1700 feet. 
Corrosion of iron and steel pipe has always been an argument against its 
use, but for about thirty years such pipe has been in use in California; and 
a life of twenty-five years is not considered the limit, when both inside and 
outside of the pipe are treated with a coating of asphalt. 

The method of covering with asphalt referred to affords perfect protec- 
tion against corrosion, and so long as the coating is intact, makes it practi- 
cally indestructible so far as all ordinary wear is concerned. The conditions 
which interfere with the best service are where the coating is worn off by 
abrasion in transportation, or where the pipe is subject to severe shock by 
the presence of air, or by a sudden closing of the gates, or where the service 
is intermittent, causing contraction and expansion, which opens the joints 
and breaks the covering. With ordinary care these objections can mostly 
be overcome. While the primary object of coating pipe in this way is to 
prevent oxidization, and thus insure its durability, it is incidentally an ad- 
vantage in providing a smooth surface on the inside, which reduces the fric- 
tion of water in its passage. 

The Coast method of laying pipe is to take the shortest practicable dis- 
tance that the ground will permit, placing the pipe on the surface and con- 
necting directly from ditch, flume, or other source of supply to the wheel. 
Avoid short turns or acute angles, as they lessen the head and produce shock. 

The ordinary method of jointing is the slip joint, made up in much the 
same way as stove-pipe. Of course this is only adapted to comparatively 
low heads, special riveted-joint construction being necessary for the higher 
falls. In laying such pipe where the lengths come together at an angle, a 
lead joint should be made. This is done by putting on a sleeve, allowing a 
space, say three-eighths of an inch, for running in lead. With a heavy 
pressure, and especially on steep grades, the lengths should be wired 
together, lugs being put on the sections forming the joints for this purpose; 
and where the grade is very steep, the pipe should be securely anchored 
with wire cable. 

In laying the pipe line it is customary to commence at the wheel, and with 
slip joint the lower end of each length should be wrapped with cotton drill- 
ing or burlaps to prevent leaking ; care being taken in driving the joints 
together not to move the gate and nozzle from their position. Some tempo- 
rary bracing may be necessary to provide against this. 

Where several wheels are to be supplied from one pipe line, a branch 
from the main in the form of the letter Y is preferable to a right angle out- 
let. When taken from the main at a right angle, the tap-hole should be 
nearly as large as the main, reducing by taper joint to the size of pipe 
attached to the wheel gate. 

It is advised where practicable to lay the pipe in a trench, covering it 
with earth. Even in warm climates, where this is not necessary as protec- 
tion from frost, it is desirable to prevent contraction and expansion by 
variations of temperature, as well as to afford security against accident. 
When laid over a rocky surface a covering of straw or manure will protect 
it from the sun, and generally prevent freezing ; as where kept in motion, 
water under pressure will stand a great degree of cold without giving 
trouble in this way. After connections are made, it should be tested before 
covering to see that the joints are tight. 

Care should be taken when the pipes are first filled to see that the air is 
entirely expelled, the use of air valves being necessary in long lines laid 
over undulating surfaces. Care should also be taken before starting to see 
that there are no obstructions in the pipe or connections to wheel, and that 
there are no leaks to reduce the pressure. Pipe lines of any considerable 
length should be graduated as to size, being larger near the top and reduced 
toward the lower end, the thickness of iron for various sizes being deter- 
mined by the pressure it is to carry. This is a saving in first cost, and 
facilitates transportation by admitting of length, being run inside of each 
other. 

When used near railroad stations, pipe is generally made in 27 ft. lengths 
for purpose of economizing freight, this being the length of a car. When 
transported long distances by wagon, it is usually made in about 20 ft. 
lengths. For pipe of large diameter, or for transportation over long dis- 
tances, as also for mule packing, it is made in sections or joints of 24 to 30 
inches in length, rolled and punched, with rivets furnished to put together 



WOODED-STAVE PIPE. 933 



on the ground where laid. Pipe of this character, being cold riveted, is 
easily put together with the ordinary tools for the purpose. In such case, 
preparation should be made for coating with asphalt before laying. 

In many cases much expense may be saved in pipe by conveying the 
water in a flume or ditch along the hillside, covering in this way a large 
part of the distance, then piping it down to the power station by a short 
line. This is more especially applicable to large plants, where the cost of 
the pipe is an important item. 

DATA FOR fllJIIIES Al¥» BITCHES. 

To jjive a general idea as to the capacity of flumes and ditches for carry- 
ing water, the following data is submitted : 

The greatest safe velocity for a wooden flume is about 7 or 8 feet per second 
For an earth ditch this should not exceed about 2 feet per second. In Califor- 
nia it is the general practice to lay a flume on a grade of about \ inch to the 
rod, or often 2 inches to the 100 feet, depending on the existing conditions. 

Assuming a rectangular flume 3 feet wide, running 18 inches deep, its 
velocity and capacity would be as shown below : — 

Grade. Vel. in Ft. per Sec. Quantity Cu. Ft. Min. 

4 inch to rod 2.6 702 

i " " " 3.7 999 

£ " " " 5.3 1,431 

As the velocity of a flume or ditch is dependent largely on its size and 
character of formation, no more specific data than the above can be given. 

It is not safe to run either ditch or flume more than about f or | full. 

WOODEHr-iTAVE PIPE. 

Although wooden-stave pipe has been in use for years on old water powers 
for penstocks, etc., it seems to have been given but little study until late 
years, when it has been used to some extent on the Pacific Coast for con- 
veying water long distances under heads not much exceeding 200 feet. Al- 
though the construction of wooden-stave pipe is quite simple, yet consider- 
able skill and care are necessary to make water-tight work. One of the 
latest pieces of work employing this type of pipe is the plant of the San 
Gabriel Los Angeles Transmission, California, — where several miles of 
wooden-stave pipe, 48 ins. diameter, are used. The pipe is laid uniformly ten 
feet below hydraulic grade ; and the wood is of such thickness as to be always 
water-soaked, and will thus outlast almost any other form of construction. 

The staves are placed so as to break joints, the flat sides are dressed to a 
true circle, and the edges to radial planes. The staves are cut off square at 
the ends, and the ends slotted, a tight-fitting metallic tongue being used to 
make the joint. 

The pipe depends upon steel bands for its strength, and in the case above 
mentioned they are of round steel rod placed ten inches apart from center 
to center. Where the pressures vary along the line, bands can be spaced 
closer or wider apart to make the necessary strength. The preference is 
given round bands over flat ones, on account of their embedding themselves 
in the wood better as it swells. They also expose less surface to rust than 
would flat ones of the same strength. The ends of the bands are secured 
together through a malleable iron shoe, having an interior shoulder for the 
head of the bolt, and an exterior shoulder for the nut, the whole band thus 
being at right angles to the line of the pipe. Where curves are not too 
sharp, they can easily be made in the wooden pipe ; but for short turns, sec- 
tions of steel-riveted pipe of somewhat larger internal diameter than that 
of the wooden pipe are introduced. The joints between wood and steel are 
made by a bell on the steel pipe that is larger than the outside diameter of 
the wooden pipe. After partly filling the space between bell and wood with 
oakum packed hard, for the remainder use neat Portland cement. 

Advantages claimed for this type are that it costs less than any other 
form, and especially so where transportation is over the rugged country 
where it is most liable to be used ; great length of life, and greater capacity 
than either cast-iron or steel-riveted. Compared with new riveted pipe, the 
carrying capacity of stave pipe is said to be from 10 to 40 % more, and this 
difference increases with age as the wooden pipe gets smoother, while the 
friction of the metal pipe increases to a considerable degree. 

As compared with open flumes, the life is so much greater and repairs so 
much less as to considerably more than counterbalance the first cost. For 
detailed information on wooden-stave pipe, see papers by A. L. Adams, 
September, 1898, Am. Soc. C= E. 



934= 



WATER-POWER. 



TAME ©E RIVETED HYDRAULIC E»IF»E. 

(Pelton Water Wheel Co.) 
Showing weight, with safe head for various sizes of double-riveted pipe. 



ft . 


ft . 

*§ 

p.p. 

<B 

7~ 
12 
12 


"8'jS 


■d'ft^r 

s« «-. ® 

0) - =+- 

W-P 50 


Cu. ft. water 
pipe will con- 
vey per min. 
at vel. 3 ft. 
per sec. 


£.5 
p, 

WfeS 

'£ *> • 

i i- CO 


1 ® 

"ft 

; go 

~18~ 
18 
IS 
18 
18 

~20~ 
20 
20 
20 
20 



ft 
ft 

oj 

si 
©.£ 

<£ 

~254 
254 
254 
254 
254 


PS 2 

o _, W 


'CS ft£ 

=* „-, a 

hHr3 CS 

hh-w m 


Cu. ft. water 
pipe will con- 
vey per min. 
at vel. 3 ft. 
per second. 


53 .a 

ft 

43 <H 


3 
4 
4 


18 
18 
16 


400 
350 

525 


9 

16 
16 


2} 

3 


! 16 

i 14 
12 

11 

10 


165 

252 
385 
424 
505 


320 
320 
320 
320 
320 


16* 

20* 

27* 


5 
5 


20 
20 

20 


18 
16 
14 


325 
500 
675 


25 
25 
25 


3* 
4} 
5 


30 
34 


5 


314 
314 
314 
314 
344 


16 
14 
12 
11 
10 


148 
227 
346 
380 
456 


400 
400 
400 
400 
400 


18 


6 
6 
6 


28 
28 
28 
38 
38 
38 


18 
16 
14 
18 
16 
14 


296 
487 
743 


36 
36 
36 


i 


22* 
30" 
32* 
36* 


7 


254 
419 

640 


50 
50 
50 


6} 

8* 


7 
7 


22 
22 
22 

22 
22 


380 
380 
380 
380 
380 


16 
14 
12 
11 
10 


135 
206 
316 
347 
415 


480 
480 
480 
480 
480 


20 

24| 

32} 

35} 

40 


8 
8 
8 


50 
50 
50 
63 
63 
63 


16 
14 
12 


367 
560 

854 


63 
63 
63 


9* 
13 




24 
24 
24 
24 
24 


452 
452 
452 
452 
452 


14 
12 
11 
10 
8 


188 
290 
318 
379 
466 


570 
570 
570 
570 
570 


27} 
35* 
39" 
43* 


9 
9 
9 


16 
14 
12 


327 
499 
761 


80 

80 
80 


8* 
10f 
Ml 


10 

10 
10 
10 
10 


78 
78 
78 
78 
78 


16 
14 
12 
11 
10 


295 
450 

687 
754 
900 


100 
100 
100 
100 
100 


9} 
HI 
15| 
17* 
191 


53 


26 
26 
26 
26 
26 
28 
28 
28 
28 
2S 
"30" 
30 
30 
30 
30 


530 
530 
530 
530 
530 


14 
12 
11 
10 
8 


175 
267 
294 
352 

432 


670 
670 
670 
670 
670 


29} 
38* 
42 
47 


11 
11 
11 
11 


95 
95 
95 
95 
95 


16 
14 
12 
11 
10 


269 
412 
626 
687 
820 


120 
120 
120 
120 
120 


9| 
13 
171 

18| 
21 


57} 


615 
615 
615 
615 
615 


14 
12 
11 
10 

8 


102 
247 
273 
327 
400 


775 
775 
775 

775 
775 


31} 

41} 

45 

50} 

61} 


12 
12 
12 
12 
12 


113 
113 
113 
113 
113 


16 
14 
12 
11 
10 


246 
377 
574 
630 
753 


142 
142 
142 
142 
142 


Hi 

14 

18* 
19| 

22} 


706 
706 
706 
706 
706 


12 
11 

10 
8 

7 


231 
254 
304 
375 

425 


890 
890 
890 

890 
890 


44 

48 
54 

65 


13 
13 
13 
13 
13 


132 
132 
132 
132 
132 


16 
14 
12 
11 
10 


228 
348 
530 
583 
696 


170 

170 
170 
170 
170 


12 
15 
20 

22 
24* 


74 


36 
36 
36 
36 


1017 
1017 
1017 
1017 


11 

10 

8 
7 


141 
155 
192 
210 


1300 
1300 
1300 
1300 


58 
67 

78 
88 


14 
14 
14 
14 
14 


153 
153 
153 
153 
153 


16 
14 
12 
11 
10 


211 
324 
494 
543 
648 


200 
200 
200 
200 
200 


13 
16 

21* 
23i 
26 




40 
40 
40 
40 
40 


1256 
1256 
1256 
1256 
1256 


10 

8 
7 
6 
4 


141 
174 
189 
213 

250 


1600 
1600 
1600 
1600 
1600 
1760 
1760 
1660 
1760 
1760 
1760 
1760 
1760 
1760 


71 

86 
97 
108 
126 




176 

176 

176 

376 

176 

20T 

201 

201 

201 

201 


16 
14 
12 
11 
10 

14 
12 
11 
10 


197 
302 
460 
507 
606 


225 
225 
225 
225 
225 


m 

17 

23 

24i 

28 




15 
15 
15 
15 
15 


42 

42 

42 

42 

42 

42 

42 

42 1 

42 


1385 

1385 
1385 
1385 
1385 
1385 
1385 
1385 
1385 


10 

8 
7 
6 
4 

1 
3 

i 


135 

165 

180 

210 

240 i 

270 

300 

321 

363 


74* 

91 
102 
114 
133 


16 
16 
16 
16 
16 


185 
283 
432 
474 
567 


255 
255 
255 
255 
255 


14* 

174 
24} 
26| 

29* 


137 
145 
177 
216 



FLOW OF WATER. 



93o 



Cubic Feet of Water per Minute IMscharg-ed Through an 
Orifice 1 Square Inch in Area. 





ifar em?/ other size of orifice, multiply by its area in square i 


riches. 




^ CD 




^ CD 




V, v 




V, <D 




V, » 




"8® 




"S® 






























05 

CD 


CD bCrJ 


no 

CD 


CD Slfirj 


OB 
CD 


CD CJCs 
CD U Z 


05 
CD 


cd Ma 

CD U S 


05 
CD 


cd Ms 
CD I- 3 


ft 


e ti h 


05 

ID 


CD bcp 
CD M S 


A 


2-2 ft 




S.2 ft 


A 


ta «*.S 




fti ^.S 


A 


Ph S-" 


A 


PH « .3 




pCj o8;.S 


05 ° 






§5£ 


33^ 


Is ® 


C3 M 


o cc h 




£-2 ft 


02 ° 


£ ES t* 


cd a 


*«£ 


CD r* 






£.S 


CD a 


cd d 


3 H * 


CD fl 


3 


1.12 


13 


2.20 


23 


2.90 


33 


3.47 


43 


3.95 


53 


4.39 


63 


4.78 


4 


1.27 


14 


2.28 


24 


2.97 


34 


3.52 


44 


4.00 


54 


4.42 


64 


4.81 


5 


1.40 


15 


2.36 


25 


3.03 


35 


3.57 


45 


4.05 


55 


4.46 


65 


4.85 


6 


1.52 


16 


2.43 


26 


3.08 


36 


3.62 


46 


4.09 


56 


4.52 


m 


4.89 


7 


1.64 


17 


2.51 


27 


3.14 


37 


3.67 


47 


4.12 


57 


4.55 


67 


4.92 


8 


1.75 


18 


2.58 


28 


3.20 


38 


3.72 


48 


4.18 


58 


4.58 


68 


4.97 


9 


1.84 


19 


2.64 


29 


3.25 


39 


3.77 


49 


4.21 


59 


4.63 


69 


5.00 


10 


1.94 


20 


2.71 


30 


3.31 


40 


3.81 


50 


4.27 


60 


4.65 


70 


5.03 


11 


2.03 


21 


2.78 


31 


3.36 


41 


3.86 


51 


4.30 


61 


4.72 


71 


5.07 


12 


2.12 


22 I 2.84 


32 


3.41 


42 


3.91 


52 


4.34 


62 


4.74 


72 


5.09 



Table Showing 1 the Theoretical Velocity and Discbarg-e in 
Cubic feet Through an Orifice of JL Square Inch Issu- 
ing- Under Heads Varying- from 1 to lOO Feet. 





Theoreti- 


Theoret- 




Theoreti- 


Theoret- 




Theoreti- 


Theoret- 


2 • 


cal Dis- 


ical 


.3 • 


cal Dis- 


ical 


a . 


cal Dis- 


ical 


51 


charge in 


Velocity 




charge in 


Velocity 


-d ® 


charge in 


Velocity 


S£ 


Ou. Ft. 


in Feet 


Cu. Ft. 


in Feet 


§& 


Cu. Ft. 


in Feet 


w 


per Min. 


per Min. 


W 


per Min. 


per Min. 


w 


per Min. 


per Min, 


1 


3.34 


481.2 


35 


19.77 


2847.6 


69 


27.74 


3997.1 


2 


4.73 


680.4 


36 


20.05 


2887.2 


70 


27.94 


4021.1 


3 


5.79 


833.4 


37 


20.33 


2926.8 


71 


28.14 


4054.5 


4 


6.68 


962.4 


38 


20.60 


2966.4 


72 


28.34 


4283.0 


5 


7.47 


1075.8 


39 


20.87 


3004.8 


73 


28.53 


4111.3 


6 


8.18 


1178.4 


40 


21.13 


3043.2 


74 


28.73 


4139.4 


7 


8.84 


1273.2 


41 


21.38 


3081.1 


75 


28.93 


4165.2 


8 


9.45 


1360.8 


42 


21.64 


3118.5 


76 


29.11 


4194.9 


9 


10.02 


1443.6 


43 


21.90 


3156.4 


77 


29.30 


4222.4 


10 


10.57 


1521.6 


44 


22.15 


3191.8 


78 


29.49 


4249.8 


11 


11.08 


1596.0 


45 


22.40 


3227.8 


79 


29.68 


4265.9 


12 


11.57 


1666.8 


46 


22.65 


3263.6 


80 


29.87 


4303.6 


13 


12.05 


1734.6 


47 


22.89 


3298.9 


81 


30.06 


4330.8 


14 


12.50 


1800.6 


48 


23.14 


3333.8 


82 


30.24 


4357.4 


15 


12.94 


1863.6 


49 


23.38 


3368.4 


83 


30.42 


4383.6 


16 


13.37 


1924.8 


50 


23.61 


3402.5 


84 


30.61 


4410.2 


17 


13.78 


1984.2 


51 


23.85 


3436.4 


85 


30.79 


4436.4 


18 


14.18 


2041.8 


52 


24.08 


3469.9 


86 


30.97 


4462.4 


19 


14.57 


2097.6 


53 


24.31 


3503.1 


87 


31.15 


4488.2 


20 


14.95 


2152.2 


54 


24.54 


3536.0 


88 


31.33 


4514.0 


21 


15.31 


2205.0 


55 


24.76 


3568.6 


89 


31.50 


4539.5 


22 


15.67 


2256.6 


56 


24.99 


3600.9 


90 


31.68 


4565.0 


23 


16.02 


2307.6 


57 


25.21 


3632.9 


91 


31.86 


4590.3 


24 


16.37 


2357.4 


58 


25.43 


3664.6 


92 


32.04 


4615.4 


25 


16.71 


2406.0 


59 


25.65 


3696.1 


93 


32.20 


4G40.5 


26 


17.04 


2453.4 


60 


25.87 


3727.3 


94 


32.38 


4665.3 


27 


17.36 


2500.2 


61 


26.08 


3758.2 


95 


32.55 


4690.1 


28 


17.68 


2545.8 


62 


26.29 


3788.9 


96 


32.72 


4714.7 


29 


17.99 


2590.8 


63 


26.51 


3819.3 


97 


32.89 


4739.2 


30 


18.30 


2635.8 


64 


26.72 


3849.6 


98 


33.06 


4763.5 


31 


18.60 


2679.0 


65 


26.92 


3879.5 


99 


33.23 


4787.8 


32 


18.90 


2722.2 


66 


27.13 


3909.2 


100 


33.40 


4812.0 


33 


19.20 


2764.2 


67 


27.33 


3938.7 








34 


19.49 


2806.2 


68 


27.54 


3968.4 









936 



WATER-POWER. 



flow of Mater Xhroug-li an Orifice. 

a =z area of orifice in square inches. 

Q = cubic feet discharged per minute. 

h = head in inches. 

Q = .624V/* x a. 
The best form of aperture for giving the greatest flow of water is a coni- 
cal aperture whose greater base is the aperture, the height or length of the 
section of cone being half the diameter of aperture, and the area of the 
small opening to the area of the large opening as 10 to 16 ; there will be no 
contraction of the vein, and consequently the greatest attaiuable discharge 
will be the result. 

OTKASUKiEJttfjflX OJP FLOW OJF WJLXISK IW JL 
iTAEAM. 

The quantity of water flowing in a stream may be roughly estimated as 
follows : 

Find the mean depth of the stream by taking measurements at 10 or 12 
or more equal distances across. Multiply this mean depth by the width of 
the stream, which will give the total cross-section of the prism. 

Find the velocity of the flow in feet per minute, by timing a float over a 
measured distance, several times to get a fair average. Use a thin float, 
such as a shingle, so that it may not be influenced by the wind. 




Fig. 13. 

The area or cross-section of the prism multiplied by the velocity per min- 
ute will give the quantity per minute in cubic feet. 

Owing to friction of the bed and banks the actual flow is reduced to about 
83 per cent of the calculated flow as above. 




Fig, 14. 



HORSE-POWER OF WATER. 



937 



Miners' Inch Measurements. 

(Pelton Water Wheel Co.) 

Miners' inch is a term much in use on the Pacific Coast and in the mining 
regions, and is described as the amount of water flowing through a hole 1 
inch square in a 2-inch plank under a head of 6 inches to the top of the 
orifice. 

Fig. 13 shows the form of measuring-box ordinarily used ; and the follow- 
ing table gives- the discharge in cubic feet per minute of a miners' inch 
of water, as measured under the various heads and different lengths and 
heights of apertures used in California. 



*w ■ rH 


Openings 2 Inches High. 


Openings 4 Inches High. 


O be 

rn _£h CO 


Head to 


Head to 


Head to 


Head to 


Head to 


Head to 


Hi 


Center, 


Center, 


Center, 


Center, 


Center, 


Center, 


5 Ins. 


6 Inches. 


7 Inches. 


5 Inches. 


6 Inches. 


7 Inches. 




Cu.Ft. 


Cu. Ft. 


Cu. Ft. 


Cu. Ft. 


Cu. Ft. 


Cu. Ft. 


4 


1.348 


1.473 


1.589 


1.320 


1.450 


1.570 


6 


1.355 


1.480 


1.596 


1.336 


1.470 


1.595 


8 


1.359 


1.484 


1.600 


1.344 


1.481 


1.608 


10 


1.361 


1.485 


1.602 


1.349 


1.487 


1.615 


12 


1.363 


1.487 


1.604 


1.352 


1.491 


1.620 


14 


1.364 


1.488 


1.604 


1.354 


1.494 


1.623 


16 


1.365 


1.489 


1.605 


1.356 


1.496 


1.626 


18 


1.365 


1.489 


1.606 


1.357 


1.498 


1.628 


20 


1.365 


1.490 


1.606 


1.359 


1.499 


1.630 


22 


1.366 


1.490 


1.607 


1.359 


1.500 


1.631 


24 


1.366 


1.490 


1.607 


1.360 


1.501 


1.632 


26 


1.366 


1.490 


1.607 


1.361 


1.502 


1.633 


28 


1.367 


1.491 


1.607 


1.361 


1.503 


1.634 


30 


1.367 


1.491 


1.608 


1.362 


1.503 


1.635 


40 


1.367 


1.492 


1.608 


1.363 


1.505 


1.637 


50 


1.368 


1.493 


1.609 


1.364 


1.507 


1.639 


60 


1.368 


1.493 


1.609 


1.365 


1.508 


1.640 


70 


1.368 


1.493 


1.609 


1.365 


1.508 


1.641 


80 


1.368 


1.493 


1.609 


1.366 


1.509 


1.641 


90 


1.369 


1.493 


1.610 


1.366 


1.509 


1.641 


100 


1.369 


1.494 


1.610 


1.366 


1.509 


1.642 



Note. — The apertures from which the above measurements were obtained 
were through material 1\ inches thick, and the lotver edge 2 inches above the 
bottom of the measuring-box, thus giving full contraction. 

FLOW OF WATER OVER WEIRS. 
Weir Dam [Measurement. 

(Pelton Water Wheel Co.) 

Place a board or plank in the stream, as shown in Fig. 14, at some point 
where a pond will form above. The length of the notch in the dam should 
be from two to four times its depth for small quantities, and longer for 
large quantities. The edges of the notch should be beveled toward the 
intake side as shown. The overfall below the notch should not be less than 
twice its depth, that is, 12 inches if the notch is 6 inches deep, and so on. 

In the pond, about 6 feet above the dam, drive a stake, and then obstruct 
the water until it rises precisely to the bottom of the notcb, and mark the 
stake at this level. Then complete the dam so as to cause all the water to 
flow through the notch, and, after time for the water to settle, mark the 
stake again for this new level. If preferred, the stake can be driven with 
its top precisely level with the bottom of the notch, and the depth of the 
water be measured with a rule after the water is flowing free, but the marks 



938 



WATER-POWER. 



are preferable in most cases. The stake can then he withdrawn ; and the 
distance between the marks is the theoretical depth of flow corresponding 
to the quantities in the table. 

Francis's Formula 1 for Weirs. 

As given by 
Francis. 
Weirs with hoth end contractions ) ^ „„,,i 

suppressed J Q — 6.66th 

Weirs with one end contraction ) _ ,. 

suppressed ) V — 6 - i6 K L ~ 



Ah) 1? 3.29Z/i 



As modified by 
Smith. 

3.29 (l+j)h % 



Weirs with full contraction 



Q — 3.33(Z — .2h)h* 3.29 1 I 



The greatest variation of the Francis formulae from the value of c given 
oy Smith amounts to 34 per cent. The modified Francis formulas, says Smith, 
will give results sufficiently exact, when great accuracy is not required, 
within the limits of h, from .5 feet to 2 feet, I being not less than 3 h. 

Q = discharge in cubic feet per second, I = length of weir in feet, h zr 
effective head in feet, measured from the level of the crest to the level of 
still water above the weir. 

If Q / = discharge in cubic feet per minute, and V and W are taken in inches, 

the first of the ahove formulas reduces to Q' — OAl'h'* • The values are suf- 
ficiently accurate for ordinary computations of water-power for weirs 
without end contraction, that is, for a weir the full width of the channel 
of approach, and are approximate also for weirs with end contraction when 
I — at least 10/i, hut about 6 per cent in excess of the truth when I = 4/t. 

Weir Tal»le. 

Table Showing the Quantity of Water Passing over Weirs in Cubic Feet 

per Minute. 



c £ 








flM 


03 ^ 


4 


« 5 O °o 


OOh 


.2^ %^%);~ 

-^ U fi o 3 <5 

= 03 08 e3 *>> 


o o - 


-^ t- x y - 1- 

.^ k « ce ^ > 


3££ 


■2^^^-&^ 

^ f-( 32 O T OJ 

J 3 a- ^ rt ^> 
Q ftftnMl> 


O O j-| 


a -ci £ 5 

•2 ^ OJ ^ "g) ^ 

•t; --i 3i' o k 03 

= i k « ^> 




4.85 


44 


50.20 


84 


- 120.18 


124 


214.32 


14 

3 


5.78 


43 


52.18 


8f 


122.82 


12| 


220.76 


6.68 


g 


54.22 


8| 


125.52 


13 


227.30 


ii 


7.80 


54 


56.25 


S3 


128.14 


13} 


233.92 


i* 


8.90 


5i 


58.33 


9 


130.93 


134 


240.54 


ii 


10.00 


5f 


60.42 


94 


133.65 


13| 


247.22 


it 


11.23 


54 


62.55 


91 


136.43 


14 


254.03 


H 


12.45 


5f 


64.68 


9| 


139.18 


141 


260.83 


2 


13.72 


51 


66.86 


9* 


141.99 


144 


267.77 


2J 


15.02 


53 


68.98 


9 f 
9| 


144.80 


14| 


274.70 


21 


16.36 


6 


71.27 


147.64 


15 


281.72 


2i! 


17.75 


8 


73.45 


9^ 


150.47 


151 


288.82 


24 


19.17 


75.77 


10 


153.35 


15* 


295.93 


1 


20.63 


1 


78.04 


10^ 


156.20 


15| 


303.10 


22.11 


80.36 


101 


159.14 


16 


310.36 


23 


23.63 


6f 


82.63 


10| 


102.07 


161 
164 


317.69 


3 


25.20 


6| 


85.04 


10| 


164.99 


325.03 


3J- 


26.78 


63 


87.43 


lOf 


167.89 


16f 


332.42 


3J 


28.43 


7 


89.82 


10| 


169.92 


17 


339.91 


3g 


30.06 


7 ? 
7} 


92.16 


103 


173.90 


13 


347.45 


34 


31.75 


94.67 


11 


176.92 


355.02 


If 


33.45 


7| 


97.11 


111 


179.94 


17| 


362.77 


35.22 


7* 


99.50 


111 


182.99 


18 


370.34 


33 


36.98 


? 


102.10 


111 


186.03 


181 


378.12 


4 


38.80 


104.63 


114 


189.13 


18| 


385.87 


4* 


40.63 


7| 


107.13 


llf 


192.20 


18| 


393.66 


41 


42.49 


8 


109.74 


111 


195.32 


19 


401.63 


4| 


44.39 


8s 


112.31 


113 


198.47 


191 


409.58 


44 


46.29 


81 


114.91 


12 


201.59 


194 


417.48 


4f 


48.22 


8f 


117.51 


121 


207.94 


19| 


425.68 



HORSE-POWER OE WATER. 



939 



TAJBJLES FOR CA1CVLATMG THII JMOI5WK-JPOWKHS 
OJf WA1EB. 

(Pelton Wheel Co.) 





miners' Incb Table. 




Cubic feet Table. 


The following table gives 


the horse- 


The following table gives the 


power of one miners' inch of water 


horse-power of 


one cubic foot of 


under heads from 


one up 


to eleven 


water per minute under heads from 1 


hundred feet. This inch 


equals 1| 


one 


up to eleven hundred feet. 


cubic feet per minute. 












p< 




a 




a 




ti 




■3© 


Horse- 


"nn-^" 


Horse- 




Horse- 


CD "£? 


Horse- 


S'r 8 


Power. 


«r® 


Power. 


Power. 


"§« 


Power. 


<bEr 




®P=h 




©Ph 




vfr 




K 




W 




W 




w 




l 


.0024147 


320 


.772704 


i 


.0016098 


320 


.515136 


20 


.0482294 


330 


.796851 


20 


.032196 


330 


.531234 


30 


.072441 


340 


.820998 


30 


.048294 


340 


.547332 


40 


.096588 


350 


.845145 


40 


.064392 


350 


.563430 


50 


.120735 


360 


.869292 . 


50 


.080490 


360 


.579528 


60 


.144882 


370 


.893439 


60 


.096588 


370 


.595626 


70 


.169029 


380 


.917586 


70 


.112686 


380 


.611724 


80 


.193176 


390 


.941733 


80 


.128784 


390 


.627822 


90 


.217323 


400 


.965880 


90 


.144892 


400 


.643920 


100 


.241470 


410 


.990027 


100 


.160980 


410 


.660018 


110 


.265617 


420 


1.014174 


110 


.177078 


420 


.676116 


120 


.2S9764 


430 


1.038321 


120 


.193176 


430 


.692214 


130 


.313911 


440 


1.062468 


130 


.209274 


440 


.708312 


140 


.338058 


450 


1.086615 


140 


.225372 


450 


.724410 


150 


.362205 


460 


1.110762 


150 


.241470 


460 


.740508 


160 


.386352 


470 


1.134909 


160 


.257568 


470 


.756606 


170 


.410499 


480 


1.159056 


170 


.273666 


480 


.772704 


180 


.434646 


490 


1.183206 


180 


.289764 


490 


.788802 


190 


.458793 


500 


1.207350 


190 


.305862 


500 


.804900 


200 


.482940 


520 


1.255644 


200 


.321960 


520 


.837096 


210 


.507087 


540 


1.303938 


210 


.338058 


540 


.869292 


220 


.531234 


560 


1.352232 


220 


.354156 


560 


.901488 


230 


.555381 


580 


1.400526 


230 


.370254 


580 


.933684 


240 


.579528 


600 


1.448820 


240 


.386352 


600 


.965880 


250 


.603675 


650 


1.569555 


250 


.402450 


650 


1.046370 


260 


.627822 


700 


1.690290 


260 


.418548 


700 


1.126860 


270 


.651969 


750 


1.811025 


270 


.434646 


750 


1.207350 


2S0 


.676116 


800 


1.931760 


280 


.450744 


800 


1.287840 


290 


.700263 


900 


2.173230 


290 


.466842 


900 


1.448820 


300 


.724410 


1000 


2.414700 


300 


.482940 


1000 


1.609800 


310 


.748557 


1100 


2.656170 


310 


.499038 


1100 


1.770780 



When the Exact Head is found in Above Table. 

Example.— Have 100 foot head and 50 inches of water. How many 
horse-power ? 

By reference to above table the horse-power of 1 inch under 100 feet 
head is .241470. The amount multiplied by the number of inches, 50, will 
give 12.07 horse-power. 

When Exact Head is not Found in Table. 

Take the horse-power of 1 inch under 1 foot head, and multiply by the 
number of inches, and then by number of feet head. The product will be 
the required horse-power. 

The above formula will answer for the cubic-feet table, by substituting 
the equivalents therein for those of miners' inches. 

Note. — The above tables are based upon an efficiency of 85 percent. 



940 



WATER-POWER. 



WATEK-WHEEJLS. 

Undershot Wheels, in which the water passes under acting by im- 
pulse, when constructed, in the old-fashioned way with flat boards as floats, 
have a maximum theoretical efficiency of 50 per cent ; but with curved floats, 
as in Poncelet's wheel, which are arranged so that the water enters without 
shock and drops from the floats into the tail-race without horizontal velo- 
city, the maximum efficiency is as great as for overshot wheels, and the 
available efficiency is found to be about 60 per cent. The velocity of the 
periphery should be about .5 of the theoretical velocity of the water due to 
the head. 

Breast and Overshot Wheels. 

The best peripheral velocity is about 6 feet per second, and for the water 
supplied to it about 12 feet per second, which is the velocity due to a fall of 
about 2\ feet ; therefore, the point at which the Avater strikes the wheel 
should be 2\ feet below the top-water level. The chief cause of loss in over- 
shot wheels is the velocity which the water possesses at the moment it falls 
from the float or bucket ; overshot Avheels are good for falls of 13 feet to 20 
feet ; below that breast wheels are preferable. The capacity of the buckets 
should be three times the volume of water held in each. The distance apart 
of the buckets may be 12 inches in high-breast and overshot wheels, or 18 
inches in low-breast wheels, while the opening of buckets may be 6 to 8 
inches in high-breast, and 9 inches to 12 inches in low-breast wheels. 

TUBBIMS. 

These may be divided into two main classes, viz., pressure and impulse 
turbines. The former may be again divided into the following : parallel- 
flow, outward-flow, and inward-flow turbines, according to the direction in 
which the water flows through the turbine in relation to its axis. 

Parallel-flow turbines, sometimes called downward-flow, are best 
suited for low falls, not exceeding say 30 feet. Fontaine's turbine is of this 
class, the wheel being placed at the bottom of the water-pipe or flume, just 
above the level of the tail-race. The water passes through guide blades and 
strikes the curved floats of the wheel. Jonval's turbine is of similar type, 
but is arranged to work partly by suction, and may be placed above the 
level of the tail-race without loss of power, which is often more convenient 
for working. The efficiency is from 70 to 72 per cent with well-designed 
wheels of this type. 




Ti- ■ n \ > 
Fig. 15. Victor Wheel set in ordinary Flume. 

Outward-flow Turbines have a someAvhat higher efficiency than the 
parallel-flow — as much as 88 per cent has been realized by Boyden's tur- 
bine ; Fourneyron's has given a maximum of 79 per cent. 

Inward-flow Turbines have been designed by Swain and others. 
Tests made on a SAvain turbine by J. B. Francis gave a maximum effi- 
ciency of 84 per cent with full supply, and with the gate a quarter open 61 
per cent, the circumferential velocity of the wheel ranging from 80 to 60 
per cent of the theoretical velocity due to the head of water. In SAvam s 
turbine the edges of the floats are vertical and opposite the guide blades, 



DIMENSIONS OF TURBINES. 



941 



the edges towards the bottom of the floats being bent into a quadrant form. 
The Victor turbine is claimed to give 88 per cent under favorable conditions. 
It receives the water upon the outside, and discharges it downward and out- 
ward, the lines of discharge occupying the entire diameter of the lower portion 
of the wheel, excepting only the space filled by the lower end of the shaft. 

Impulse Tnrbineis are suitable for very high falls. The Girard and 
Pelton are both of this type. It is advised that pressure turbines be used 
on heads of 80 feet or 100 feet, bvit above this an impulse turbine is best. 
A Girard turbine is working under a fall of 650 feet. 
Installing* Turbines. 

Particular attention must be paid to the designing and construction of 
water-courses. The forebay leading to the flume should be of such size that 
the velocity of the water never exceeds 11 feet per second, and should be 
free from abrupt turns or other defects likely to cause eddies. The tail-race 
should have similar capacity and sufficient depth below the surface of the 
stream to allow at least 2 feet of dead water standing when the wheels are 
not in motion, and with large wheels, 3 feet to 4 feet ; after extending sev- 
eral feet beyond the flume, this may be gradually sloped up to the level of 
the stream. It is not uncommon to see 2 feet or 3 feet of head lost in 
defective races. 

When setting turbines some distance above the tail-race, the mouth of the 
draft-tube must be 2 inches to 4 inches below the lowest level of the stand- 
ing tail-water. Theoretically draft-tubes may be 30 feet long ; but 20 feet 
is as long as is desirable on account of the difficulty of keeping air-tight ; 
they should be made as short as possible by placing the turbine at the 
bottom of the fall. 

Particulars of the setting recommended for Victor turbines are given 
below, as an example. 

Table of Dimensions of Victor Turbine. 





A. 


B. 


C. 


D. 


E. 


F. 


K. 


"3 


1) 


i «5 

«h 1 - % 




=H 


4J 05 

5 £ 


4H f-k rl 


r'i a o 


4i^_l 


0) 

.fl 

.2^ 


o 

N 

55 


Diameter o 
Cylinder ps 
ing througl 
Floor of Fh 


°A 

S£a5 

5wo 


O 
*H 

fl 03 03 

III 

55S 


Length of S 
from Flang 
Resting on 
Floor of Fl 
to Center o 
Coupling. 


Diameter o 
Bore of Up 
Half of Coi 
ling. 


Length of < 
inder passi 
through Fl 
of Flume. 


Depth of P 
from End c 
Cylinder to 
Bottom of 
Wheel-Pit. 


a o a) 
Jgl 


In. 


In. 


In. 


Ft. 


In. 


In. 


In. 


SSis 


Lbs. 


6 


10 


131 


2 


12 


1 


5! 


sfitf£$ 


165 


8 


13* 


17* 

20J 


2* 


1914 


U 7 n 


6$ 


.3 ^"S^J 


260 


10 


16 


3" 


22| 


ill 


7* 


-o^m a a 


350 


12 


18i 3 * 


23 T 3 B - 


31 


28* 


n 5 e 


9f 


gO_J.cS 


500 


15 


9S s 

If 


28^ 
31i 


4 


33| 


2t 7 b 


11 


8>3 8 


830 


17.| 


5 


351 


911 


12! 


c^~ £ 


1125 


20 


30J 


35* 


6 


37* 


3& 


13i 


art ce a 


1475 


221 


33J 


38| 
40| 


6* 


42 


3/b 


141 


03 a o^ 


1900 


25 


354 


61 


43f 


3ii 


151 


^° , o,'S 


2335 


27J 


38! 
40| 


431 


7i 


48M 


3*1 


16| 


<w eS £ 


3225 


30 


46 


8" 


50! 


n 


191 


3540 


321 


43i 


49* 


9 


55f 


oo_CE:3 


4500 


35" 


46| 


53" 


9 


59 


n 


20 


2j^§ 


5450 


40 


56*. 


60i 


10 


64| 


22 




7500 


44 


65i 


11 


67i 


5| 


24 


9380 


48 


60i 


701 


12 


74f 


6| 


26 


O O rn O o5 


11700 


55 


68 


80 


14 


85J 


7! 


28 


£gs*§ 


19000 


6) 


80J 


92 


16 


96* 


7* 


32 


.2 -~ S c3 





DiinE]y§iO]¥§ ©;f tibbiiei. 

Tables of sizes of turbine wheels vary so much under different makers, 
and are so extensive, as not to permit their insertion here, but through the 
kindness of Mr. Axel Ekstrom of the General Electric Company I am per- 
mitted to print the following sheets of curves for the McCormick type 
turbine and. the Pelton impulse wheel. From them may be made deter- 
minations of dimensions in much shorter time than is necessary by use of 
tables. 



942 



WATER-POWER. 



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Fig. 16. 



DIMENSIONS OF TURBINES. 



943 



_TX S 


0009T 


°L_ > .§ S 


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t * -s .a 


00051 y 


X 4 S"g§ 8 


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V U «l ££" 3 


Ti *> y 


V V -1 o . J o 


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A \ o ^ - rfS 


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v -A: <£ I's 




V 3 Q 3 ± *§ 




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oooc ji ^y jg> g 


V ^ _4\ j_ ag 




$ L. 3 - | S 




\ 5 f |g 


±-t^ ~¥^ 


V ^ 4 " 2 




\ V V £§ 


/ ^'A o 


\ r V 5 I§ 


__Ty -^ ^pst 


^ s V t § 




s ^ -N ^3 § 


_+y jMt °o 


t s ^ \ ^ V § 


o# 4aP => 2 


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^"^ ^S ^<-\ g 


/ «\> * £ 


^fc N s v ° 


Ti k$^ M I 


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Sh ^ ^. Sa: 


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S'S \ 5 =o'-'2 


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Fig. 17. 



944 WATER-POWER. 



THE IMPUIiE WATER-WHEEL. 

Mr. Ross E. Browne states that " The functions of a water-wheel, operated 
by a jet of water escaping from a nozzle, is to convert the energy of the jet, 
due to its velocity, into useful work. In order to utilize this energy fully, 
the wheel bucket, after catching the jet, must bring it to rest before dis- 
charging it, without inducing turbulence or agitation of the particles. This 
cannot be fully effected, and unavoidable difficulties necessitate the loss of 
a portion of the energy. The principal losses occur as follows : 

" First : In sharp or angular diversion of the jet in entering, or in its 
course through the bucket, causing impact, or the conversion of a portion of 
the energy into heat instead of useful work. 

" Second : In the so-called frictional resistance offered to the motion of 
the water by the wetted surfaces of the buckets, causing also the conver- 
sion of a portion of the energy into heat instead of useful work. 

" Third : In the velocity of the water as it leaves the bucket, represent- 
ing energy which has not been converted into work. 

" Hence, in seeking a high efficiency, there are presented the following 
considerations : 

" 1st. The bucket surface at the entrance should be approximately paral- 
lel to the relative course of the jet, and the bucket should be curved in such 
a manner as to avoid sharp angular deflection of the stream. If, for exam- 
ple, a jet strikes a surface at an angle and is sharply deflected, a portion of 
the water is backed, the smoothness of the stream is disturbed, and there 
results considerable loss by impact and otherwise. 

2d. The number of buckets should be small, and the path of the jet in the 
bucket short ; in other words, the total wetted surface should be small, as 
the loss by friction will be proportional to this. 

" A small number of buckets is made possible by applying the jet tangen- 
tially to the periphery of the wheel. 

" 3d. The discharge end of the bucket should be as nearly tangential to 
the wheel-periphery, as compatible with the clearance of the bucket which 
follows ; and great differences of velocity in the parts of the escaping 
water should be avoided. In order to bring the water to rest at the dis- 
charge end of the bucket, it is easily shown mathematically that the velo- 
city of the bucket should be one-half the velocity of the jet. 

" An ordinary curved or cup bucket will cause the heaping of more or less 
dead or turbulent water in the bottom of the bucket. This dead water is 
subsequently thrown from the wheel with considerable velocity, and repre- 
sents a large loss of energy. 

" The introduction of the wedge in the bucket is an efficient means of 
avoiding this loss." 

Wheels of this type are very efficient under high heads of water, and have 
been used to a great extent in the extreme western parts of the United 
States, where the fall is in hundreds of feet. It is difficult to say at what 
point of head the efficiency becomes such as to induce the use of some other 
form of wheel; but at 200 feet head the efficiencies of both impulse and tur- 
bine will be so much alike that selection must be governed by other factors. 

Tests of one of the leading impulse wheels show efficiencies varying from 
80 % to 86 % according to head and size of jet. However, many factors 
besides the efficiency enter into selection of water-wheels, which must be 
subject to local conditions, and as in most water-power plants, each is a 
special case by itself, and selection of apparatus best fitted in all ways must 
govern. 



SHAFTING, PULLEYS, BELTING, ROPE- 
DRIVING. 

Thurston gives the following formulae for calculating power and size of 
shafting. 

H.P. = horse-power transmitted. 
d =r diameter of shaft in inches. 
r = revolutions per minute. 



f (Pj- ' s / 

For head shafts well | For iron > H - p - — ^ d = \ 



125 H.P. 



r 



supported against<! For cold _ 8 / 7 , „ p 

springing. r'lledironJT.P. 



L 75 



(^ Jr r, d s r 7 « 3 /90 H.P. 



For line shafting | For iron > Hp - — 9J3 

hangers 8 feet ^ For co i d ^ 3/55^^7 

a P ai r - r'lld iron,H.P. = - — ; d = 1/ — 

^ 55 V r 

For transmission I For iron > ffjP - = ^ <* = V ~ r " 

simply, no pul- X F cold- rf l 3 /35^p; 

ie y s - r lid iron, H.P.— — — ; d = V 

^ 35 ' ▼ r 

Jones and Laughlin's use the same formulae, with the following excep- 
tions : 

d 3 r 3 /i 

For line shafts, cold-rolled iron, H.P. = — — ; d=y 

For transmission and for short-counters, 

_ „ „ ePr 3 /50 H.P. 
Turned iron H.P. = -t— ; d = y • 



Cold-rolled iron H.P.= ^; d=\/ 30 H ' P ' 

oO ' r 



50 H.P. 


r 


50 H.P. 


r 



Pulleys should he placed as near to bearings as practicable, but care 
should be taken that oil does not drip from the box into the pulley. 

The diameter of a shaft safe to carry the main pulley at the center of a 
bay may be found by multiplying the fourth power of the diameter obtained 
by the formulae above given, by the length of the bay, and dividing the pro- 
duct by the distance between centers of bearings. The fourth root of the 
quotient will be the required diameter. 

Tbe following table is based upon the above rule, and is substantially 
correct : 

945 



946 



SHAFTING, PULLEYS, BELTING, ETC. 



Hk»& 


Diameter of Shaft necessary to carry the Load at the Center of 


s-SMj 


a Bay, which is from Center to Center of Bearings. 


"S 2 « 




g^Ss-c 














2Jft. 


3 ft. 


34 ft. 


4 ft. 


5 ft. 


6 ft. 


8 ft. 


10 ft. 


















in. 


in. 


in. 


in. 


in. 


in. 


in. 


in. 


in. 


2 


24 


2i 


2| 


24 


ft 


2| 


1 


3 


2} 


24 


2| 


2} 


1 

3| 


3 


34 


3f 


3 


3 


34 


3i 


34 


3| 


4 


4i 


34 




3* 


3f 


4 


4! 


44 


% 


4 




4: 


44 


4i 


44 


4i 


54 


4* 
5 






44 
5 


4f 
54 
54 
6 


a 


3 


54 
6 


s 


54 
6 








5| 
6| 


6 

6§ 


it 


61 
74 



Should the load he placed near one end of the bay, multiply the fourth 
power of the diameter of shaft necessary to safely carry the load at the cen- 
ter of the bay (see above table) by the product of the two ends of the shaft, 
and divide this product by the product of the two ends of the shaft where 
the pulley is placed in the center. The fourth root of this quotient will be 
the required diameter. 

A shaft carrying both receiving and driving pulleys should be figured as 
a head-shaft. 

Deflection of Shafting-. 

(Pencoyd Iron Works.) 

As the deflection of steel and iron is practically alike under similar con- 
ditions of dimensions and loads, and as shafting is usually determined by 
its transverse stiffness rather than its ultimate strength, nearly the same 
dimensions should be used for steel as for iron. 

For continuous line-shafting it is considered good practice to limit the 
deflection to a maximum of T 4 D of an inch per foot of length. The weight 
of bare shafting in pounds — 2.6 d 2 L = W, or when as fully loaded with 
pulleys as is customary in practice, and allowing 40 lbs. per inch of width 
for the vertical pull of the belts, experience shows the load in pounds to be 
about 13 cPL = W. Taking the modulus of transverse elasticity at 26,000,000 
lbs., we derive from authoritative formulae the following : 



L = ^873 d 2 , d = V -~5, for bare shafting; 



g/l75(Z 2 , d 



s' 



, for shafting carrying pulleys, etc.; 



L being the maximum distance in feet between bearings for continuous 
shafting subjected to bending stress alone, d = diam. in inches. 

The torsional stress is inversely proportional to the velocity of rotation, 
while the bending stress ivill not be reduced in the same ratio. It is there- 
fore impossible to write a formula covering the whole problem and suffi- 
ciently simple for practical application, but the following rules are correct 
within the range of velocities usual in practice. 

For continuous shafting so proportioned as to deflect not more than T -J w 
of an inch per foot of length, allowance being made for the weakening 
effect of key-seats, 



fe y^5 



L = ^/700rf 2 for bare shafts 



SHAFTING. 



94' 



•\r 



L = 1/ 140d 2 , for shafts carrying pulleys, etc. 



d — diam. in inches, L = length in feet, r = revols. per minute. 

The following table (by J. B. Francis) gives the greatest admissible dis- 
tances between the bearings of continuous shafts subject to no transverse 
strain, except from their own weight. 



Distance between 
Bearings in ft. 

Diam. of Shaft, Wrought-iron Steel 
in inches Shafts. Shafts, 

2 15.46 15.89 

3 17.70 18.19 

4 19.48 20.02 

5 20.99 21.57 



Distance between 
Bearings in ft. 



Diam. of Shaft, Wrought-iron Steel 
in inches. Shafts. Shafts 

6 22.30 22.92 

7 23.48 24.13 

8 24.55 25.23 

9 25.53 26.24 



The writer prefers to apply a formula in all cases rather than use tables, 
as shafting is nearly always one-sixteenth inch less in diameter than the 
sizes quoted. The following tables are made up from the formulae first 
given in this chapter. 

Horse-Power Transmitted by Turned Iron Shafting-. 

As Prime Mover or Head Shaft well Supported by Bearings. 



Revolutions per Minute. 



100 125 150 175 200 225 250 275 300 



Ins. 
If 

2 



H.P. 
2.6 
3.8 
5.4 
7.5 

10 

13 

16 

20 

25 

30 

43 

60 

80 



H.P. 

3.4 
5.1 
7.3 

10 

13 

17 

22 

27 

33 

41 

58 

80 
106 



H.P. 
4.3 
6.4 

8.1 

12.5 

16 

20 

27 

34 

42 

51 

72 
100 
133 



H.P. 
5.4 

8 
10 
15 
20 
25 
34 
42 
52 
64 
90 
125 



H.P. 
6.4 
9.6 

12 

18 

24 

30 

40 

51 

63 

76 
108 
150 
199 



H.P. 

7.5 
11.2 
14 

22 

28 

35 

47 

59 

73 

89 
126 
175 
233 



H.P. 

8.6 

12.8 

16 

25 

32 

40 

54 

68 

84 
102 
144 
200 
266 



H.P. 

9.7 

14.4 

18 

28 

36 

45 

61 

76 

94 
115 
162 
225 
299 



H.P. 

10.7 

16 

20 

31 

40 

50 

67 

85 
105 
127 
180 
250 
333 



H.P. 

11.8 

17.6 

22 

34 

44 

55 

74 

93 
115 
140 
198 
275 



H.P. 

12.9 

19.2 

24 

37 

48 

60 

81 
102 
126 
153 
216 
300 
400 



Approximate Centers of Bearing's for Wrought Iron line 
Shafts Carrying- a Fair Proportion of Pulleys. 


Shaft, Diameter Inches . . 


1* 


If 


2 


k 


2i 


24 


3 


H 


4 


4J 


c. to c. Bearings —Feet . . 


7 


71 


8 


Si 


9 


9* 


10 


11 


12 


13 


Shaft, Diameter Inches . . 


5 


Sh 


6 


6i 


7 


n 


8 


9 


10 


c. to c. Bearings — Feet . . 


13J 


14 


15 


15k 


16 


17 


18 


19 


20 



948 



SHAFTING, PULLEYS, BELTING, ETC. 



Line-shafting, Bearings 8 ft. Apaet. 



g 

P 








Revolutions per Minute. 








100 


125 


150 


175 


200 


225 


250 


275 


300 


325 


350 


Ins. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


If 


6 


7.4 


8.9 


10.4 


11.9 


13.4 


14.9 


16.4 


17.9 


19.4 


20.9 


H 


7.3 


9.1 


10.9 


12.7 


14.5 


16.3 


18.2 


20 


21.8 


23.6 


25.4 


2 


8.9 


11.1 


13.3 


15.5 


17.7 


20 


22.2 


24.4 


26.6 


28.8 


31 


2* 


10.6 


13.2 


15.9 


18.5 


21.2 


23.8 


26.5 


29.1 


31.8 


34.4 


37 


2* 


12.6 


15.8 


19 


22 


25 


28 


31 


35 


38 


41 


44 


2f 


15 


18 


22 


26 


29 


33 


37 


41 


44 


48 


52 


2£ 


17 


21 


26 


30 


34 


39 


43 


47 


52 


56 


60 


2| 


23 


29 


34 


40 


46 


52 


58 


64 


69 


75 


81 


3 


30 


37 


45 


52 


60 


67 


75 


82 


90 


97 


105 


I 


3-8 


47 


57 


66 


76 


85 


95 


104 


114 


123 


133 


47 


59 


71 


83 


95 


107 


119 


131 


143 


155 


167 


58 


73 


88 


102 


117 


132 


146 


162 


176 


190 


205 


4 


71 


89 


107 


125 


142 


160 


178 


196 


213 


231 


249 



POWER TRANSMISSION ONLY. 









Revolutions per Minute. 








100 


125 


150 


175 


200 


233 


267 


300 


333 


367 


400 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


6.7 


8.4 


10.1 


11.8 


13.5 


15.7 


17.9 


20.3 


22.5 


24.8 


27.0 


8.6 


10.7 


12.8 


15 


17.1 


20 


22.8 


25.8 


28.6 


31.5 


34.3 


10.7 


13.4 


16 


18.7 


21.5 


25 


28 


32 


36 


39 


43 


13.2 


16.5 


19.7 


23 


26.4 


31 


35 


39 


44 


48 


52 


16 


20 


24 


28 


32 


37 


42 


48 


53 


58 


64 


19 


24 


29 


33 


38 


44 


51 


57 


63 


70 


76 


22 


28 


34 


39 


45 


52 


60 


68 


75 


83 


90 


27 


33 


40 


47 


53 


62 


70 


79 


88 


96 


105 


31 


39 


47 


54 


62 


73 


83 


93 


104 


114 


125 


41 


52 


62 


73 


83 


97 


111 


125 


139 


153 


167 


54 


67 


81 


94 


108 


126 


144 


162 


180 


198 


216 


68 


86 


103 


120 


137 


160 


182 


205 


228 


250 


273 


85 


107 


128 


150 


171 


200 


228 


257 


285 


313 


342 



Horse-power Transmitted Uy Cold-rolled Iron Shafting-. 

AS PRIME MOVER OR HEAD SHAFT WELL SUPPORTED BY BEARINGS. 



s 
3 








Revolutions per 


Minute. 








60 


80 


100 


125 


150 


175 


200 


225 


250 


275 


300 


Ins. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


1* 


2.7 


3.6 


4.5 


5.6 


6.7 


7.9 


9.0 


10 


11 


12 


13 


n 


4.3 


5.6 


7.1 


8.9 


10.6 


12.4 


14.2 


16 


18 


19 


21 


2 


6.4 


8.5 


10.7 


13 


16 


19 


21 


24 


26 


29 


32 


2* 


9 


12 


15 


19 


23 


26 


30 


34 


38 


42 


46 


2£ 


12 


17 


21 


26 


31 


36 


41 


47 


52 


57 


62 


2f 


16 


22 


27 


35 


41 


48 


55 


62 


70 


76 


82 


3 


21 


29 


36 


45 


54 


63 


72 


81 


90 


98 


108 


3\ 


27 


36 


45 


57 


68 


80 


91 


103 


114 


126 


136 


it 


34 


45 


57 


71 


86 


100 


114 


129 


142 


157 


172 


42 


56 


70 


87 


105 


123 


140 


158 


174 


193 


210 


4 


51 


69 


85 


106 


128 


149 


170 


192 


212 


244 


256 


Us 


73 


97 


121 


151 


182 


212 


243 


273 


302 


333 


364 



SHAFTING. 



LINE-SHAFTING, BEARINGS 8 FT. APART. 



949 











Revolutions pe 


• Minute. 








s 


100 


125 


150 


175 


200 


225 


250 


275 


300 


325 


350 


Ins. 


H.P. 


HP. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


n 


6.7 


8.4 


10.1 


11.8 


13.5 


15.2 


16.8 


18.5 


20.2 


21.9 


23.6 


n 


8.6 


10.7 


12.8 


15 


17.1 


19.3 


21.5 


23 6 


25.7 


28.9 


31 


n 


10.7 


13.4 


16 


18.7 


21.5 


24.2 


26.8 


29.5 


32.1 


34.8 


39 


n 


13.2 


16.5 


19.7 


23 


26.4 


29.6 


32.9 


36.2 


39.5 


42.8 


46 


2 


16 


20 


24 


28 


32 


36 


40 


44 


48 


52 


56 


2* 


19 


24 


29 


33 


38 


43 


48 


52 


57 


62 


67 


2* 


22 


28 


34 


39 


45 


50 


56 


61 


68 


74 


80 


2# 


27 


33 


40 


47 


53 


60 


67 


73 


80 


86 


94 


2^ 


31 


39 


47 


54 


62 


69 


78 


86 


93 


101 


109 


2^ 


41 


52 


62 


73 


83 


93 


104 


114 


125 


135 


145 


3 


54 


67 


81 


94 


108 


121 


134 


148 


162 


175 


189 


3+ 


68 


86 


103 


120 


137 


154 


172 


188 


205 


222 


240 


3* 


85 


107 


128 


150 


171 


192 


214 


235 


257 


278 


300 



POWER TRANSMISSION AND SHORT COUNTERS. 



a 








Revolutions pei 


Minute. 








s 


100 


125 


150 


175 


200 


233 


267 


300 


333 


367 


400 


Ins. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H 


6.5 


8.1 


9.7 


11.3 


13 


15.2 


17.4 


19.5 


21.7 


23.9 


26 


1« 


8.5 


10.7 


12.8 


15 


17 


19.8 


22.7 


25.5 


28.4 


31 


34 


H 


11.2 


14 


16.8 


19.6 


22.5 


26 


30 


33 


37 


41 


45 


If 


14.2 


17.7 


21.2 


24.8 


28.4 


33 


38 


42 


47 


52 


57 


1| 


18 


22 


27 


31 


35 


41 


47 


53 


59 


65 


71 


11 


22 


27 


33 


38 


44 


51 


58 


65 


72 


79 


87 


2 


26 


33 


40 


46 


53 


62 


71 


80 


88 


97 


106 


2£ 


32 


40 


47 


55 


63 


73 


84 


95 


105 


116 


127 


a* 


38 


47 


57 


66 


76 


89 


101 


114 


127 


139 


152 


n 


44 


55 


•66 


77 


88 


103 


118 


133 


148 


163 


178 


u 


52 


65 


78 


91 


104 


121 


138 


155 


172 


190 


207 


n 


69 


84 


99 


113 


138 


161 


184 


207 


231 


254 


277 


3 


90 


112 


135 


157 


180 


210 


240 


270 


300 


330 


360 



Hollow Shafts. 

Let d be the diameter of a solid shaft, and d % d 2 the external and internal 
diameters of a hollow shaft of the same material. Then the shafts will be 

d 4- (7 4 

of equal torsional strength when d s = 1 - • A 10-inch hollow shaft with 

Ctf 

internal diameter of 4 inches Avill weigh 16% less than a solid 10-inch shaft, 
but its strength will be only 2.56 % less. If the hole were increased to 5 
inches diameter the weight would be 25 % less than that of the solid shaft, 
and the strength 4.25 % less. 

Table for Laying- Out Shafting-. 

The table on the following page is used by Wm. Sellers & Co. for the lay- 
ing out of shafting. 



950 



SHAFTING. PULLEYS, BELTING, ETC. 



3 



1- I 



•saipiri 






sen 'xog jo 3ui 
jBag jo q^gueT 



w «* io 3> «>V- s^oo 35 © i-* cTirt^t-. t- oToT 



iiiot- oooi Ot"N« ^W oo OS 



SiS^gS 



;22S5SS8338S 



2 " <v e »* 



« s « -. 3 * 









o 
c 



g a-" 5 5 fa 



E. 3 3* «? ™ 



^J ™ 41 03 ^J*C 

S % o "5 •■= •« 






i««w 



SS83J 



I <N C-4 S ?? 5 



sffgsisis 






^ssssfugsf 



lA'Ot^OOC^'-JieiiA 
"-< — — •■" — ?1 <N <N C-l 



irt In'co t- oo a. ©~Vi 






rjciT^icat-aS 1 



: O -S * 

u = 



n « -e ?r * = 



*H —I M CI M C5 «l 



S^c?-^ 



2»r c s = 

,5 53 •/) — -~ v 
"3,5 « * «i =■ 

g'.'S 60= £ 

o u js ^ — *i 

«*-« S 

C <g 4> ® SPg 



l x 3 



I 



£a5 to 



I O ~ u ZJ 



r -hf~*N«(T — r*-le» -*N HN -*N -fN 

ie^dC40irooco'*"*i/;o^«t-t-.oo 



■ rfm u?«0 3?t^r- afo — ©Te^T^X'S!?!?' 



BELTING. 951 



pu ule Y§. 

Unwin says the number of arms is arbitrary, and gives tbe following 
values : 

a =z Number of arms = for a single set = 3 ,-4- T^r • 

d = diameter pulley. 

t = thickness of edge of rim of pulley = .75 inches -+- .005tf. 
T = thickness of middle of rim of pulley = It -4- c. 
b = breadth of rim of pulley = § (£ + 0.4). 
B = breadth of belt. 

f z lb~d 

for single belt = .6337 V — 
breadth of arm at hub -i a 

s /b~~d 
for double belt : 



" a 



h r — breadth of arm at rim = § h. 
e = thickness of arm at hub = 0.4 h. 
e x — thickness of arm at rim =r 0.4 h 1 . 
c = crowning ±= ^ b. 
L =i length of hub =z about f b. 

Reuleaux says pulleys of more than one set of arms may be considered 
as separate pulleys, except proportions of arms may be 0.8 to 0.7 that of 
single-arm pulleys. 

To JFind Size of Pulley. 

D = diameter of driver, or No. teeth in gear. 
d =i diameter of driven, or No. teeth in pinion. 
Rev =z revolutions per minute of driver. 
rev = revolutions per minute of driven. 

^ d x rev _ d x rev 

D = — B Rev =z j- 

Rev D 

D x Rev D x Rev 

d = rev = ; 

rev d 

KKLTIXfW. 

The coefficient of friction of belts on pulleys varies greatly, and it is there 
fore customary to use some arbitrary formula that has proved safe in 
practice. 

d — : diameter pulley in inches. 
■nd =z circumference. 
v = velocity of belt (or pulley face) in feet per minute. 
a = angle of arc of contact, commonly assumed as 180°. 

I = length of arc of contact in feet =z — t^tt- 

F= tractive force per square inch cross-section of belt. 
w — width of belt in inches. 
t = thickness of belt in inches. 

F 
S = tractive force per inch of width = — - 

rpm = revolutions per minute. 

7T d 

X rpm. 



H. P.= 



12 

v w S d w S x rpm 

33000 — 126050 



A rule in common use for approximate determination of the H.P. of belts 
is, that a single belt 1 inch wide, traveling 1000 feet per minute, will trans- 
mit 1 horse-power. This corresponds to a strain on the belt of 33 lbs. per 
inch of width. 



952 



SHAFTING, PULLEYS, BELTING, ETC. 



Authorities say single belts can be safely worked at 45 lbs. strain per 

square inch, and on this basis 

jt -p v w _ div x rpm 

' " *~ "733 ~~ 2800 

Double belts are said to be able to transmit power in the ratio of 10 to 7 

for single belts. 

tt ™ e a to i T4. v w dw x rpm 
H. P. of double belts = m = ^ • 

If the double belt is twice the thickness of the single belt, then it is fair 
to assume that it will transmit twice the power, and 

v w d w x rpm 

366 ~ 1400 

A. JF. Nag-le (Trans. A. S.M.E., vol. ii. 1881) gives the following 
formuia 

/F— 0.012 T /2 \ 



H. P. of double belt 



H. P. = CVtw 



550 



"Where C : 



J l()-.00758fa # 

coefficient of friction. 



Horse-Power of a Belt one Inch Wide, Arc of Contact ISO . 
Comparison of Different Formulae,. 



a 


a 


■ 'r< 










Form. 5 


Nagle's 


Form. 






^ft 


Form. 1 


Form. 2 


Form. 3 Form. 4 


Double. 


3V single 


■P 4)^ 


-£ 3? ® 


sPQs 
5V1S 


H,P. = 
wv 
550" 


H.P. = 
wv 
1100 


H.P. = 
wv 
1000 


H.P. = 

wv 
733' 


Belt 
H.P. = 

wv 


Belt. 


» © a? 


Laced. 


Riveted. 


r*Wtf2 


k^S 










513 






10 


600 


50 


1.09 


.55 


.60 


.82 


1.17 


.73 


1.14 


20 


1200 


100 


2.18 


1.09 


1.20 


1.64 


2.34 


1.54 


2.24 


30 


J800 


150 


3.27 


1.64 


1.80 


2.46 


3.51 


2.25 


3.31 


40 


2400 


200 


4.36 


2.18 


2.40 


3.27 


4.68 


2.90 


4.33 


50 


3000 


250 


5.45 


2.73 


3.00 


4.09 


5.85 


3.48 


5.26 


60 


3600 


300 


6.55 


3.27 


3.60 


4.91 


7.02 


3.95 


6.09 


70 


4200 


350 


7.63 


3.82 


4.20 


5.73 


8.19 


4.29 


6.78 


80 


4800 


400 


8.73 


4.36 


4.80 


6.55 


9.36 


4.50 


7.36 


90 


5400 


450 


9.82 


4.91 


5.40 


7.37 


10.53 


4.55 


7.74 


100 


6000 


500 


10.91 


5.45 


6.00 


8.18 


11.70 


4.41 


7.96 


jlO 


6600 


550 












4.05 


7.97 


120 


7200 


600 












3.49 


7.75 



Width of Belt for a g-iven Horse-Powei 

The width of belt required for any given horse-power may 
by transposing the formulas for horse-power so as to give the 
Thus : 

_, . ... 550 H.P. 9.17H. P. 2101H. P. 

From formula (l), w = = 



From formula (2), w = 
From formula (3), tv = 
From formula (4), to = 
From formula (5),* w = 



nop h.p. 

v 
1000 H. P. 



733 H. 

v 
513H. 

v 



P. 



9.17H .P. 

V 
18.33 H. P. 

V 
16.67 H. P. 

V 
12.22 H. P. 

V 
8.56 H. P. 



d x rpm 
4202 H. P. 

d x rpm 
38. 20 H. P. 

d X rpm 
2800 H. P . 

d X rpm 
1960 H. P. 



be obtained 
value of w. 

_ 2 75 H. P. 

~ L X rpm' 

_ 530 EL P. 

~ L X rpm 

_ 500 H. P. 

~ L x rpm 
360 H. P. 



L X rpm 

257 H. P. 



d x rpm L X rpm 



* For double belts. 



BELTING. 



953 



X 3.1416 



]+p 



X distance 



Length of Belt. 

Approximate rule ; two pulleys I ^-^ 

between centers] = length of belt. 

Length of Belt in Boll. 

Outside diameter roll in inches -f- diameter bole x number turns X .1309 
=: length of belt in inches for double belt. 

Weight of Belt (approximate). 

Length in feet x width in inches . ,, . . , , .. _.. . . , _ . 
s j- — weight of single belt. Divide by 8 for 

double belts. 

Hom'-Power Transmitted l»y ligrht, Bouble landless 
Leather Belting*. 

(Buckley.) 



Width, 
Inches. 


4 


6 


8 


10 


12 


14 


16 


18 


20 


22 


24 


•S 2000 


14 


22 


29 


36 


43 


50 


58 


65 


72 


80 


87 


B 2400 


17 


26 


35 


44 


52 


60 


70 


78 


88 


96 


105 


& 2800 


20 


30 


40 


51 


61 


71 


81 


91 


102 


112 


122 


& 3000 


22 


33 


44 


54 


65 


76 


87 


98 


108 


120 


131 


•g 3500 


25 


38 


50 


63 


76 


89 


101 


114 


127 


140 


153 


© 4000 


29 


43 


58 


73 


87 


101 


116 


131 


145 


160 


174 


] 4500 
•- 5000 


32 


49 


65 


82 


98 


114 


131 


147 


163 


180 


196 


36 


55 


73 


91 


109 


127 


145 


163 


182 


200 


218 


"S 5500 


40 


60 


80 


100 


120 


140 


160 


180 


200 


220 


240 


S 6000 

CO 


44 


65 


87 


109 


130 


153 


175 


200 


218 


240 


260 



(Speed X width -f-550 = horse-power, light, double.) 
(Horse-power X 550 -f- speed = width, light, double.) 



Horse-Power Transmitted by Heavy, Doable Endless 
JLeatner Belting*. 



Width, 
Inches. 


4 


6 


8 


10 


12 


14 


16 


18 


20 


22 


24 


.5 2000 


18 


27 


36 


43 


51 


60 


70 


80 


86 


96 


104 


£ 2400 


21 


31 


42 


53 


62 


72 


83 


94 


105 


115 


120 


per 


24 


36 


48 


61 


73 


85 


96 


109 


122 


135 


146 


27 


40 


53 


65 


78 


90 


104 


118 


129 


144 


157 


^ 3500 


30 


45 


60 


75 


91 


106 


121 


137 


152 


168 


184 


© 4000 


35 


52 


70 


88 


104 


121 


139 


157 


174 


192 


209 


" 4500 
P 5000 


38 


59 


78 


98 


118 


137 


157 


176 


196 


216 


235 


43 


66 


87 


110 


130 


152 


174 


196 


218 


240 


262 


% 5500 


48 


72 


96 


120 


144 


168 


192 


216 


240 


264 


288 


© 6000 


52 


78 


104 


122 


153 


183 


210 


240 


262 


288 


312 

























(Speed x width — 460 = horse-power, heavy, double.) 
(Horse-power x 460 ■— speed = width, heavy, double.) 



954 



SHAFTING, PULLEYS, BELTING, ETC. 



BOPS l»ISfl VJLJtfCi. 

C = Circumference of rope in inches. 
D=z Diameter of pulley in feet. 
11= Revolutions per minute. 



Horse-power of Rope 



200 



H.P. 



or, Half the diameter of rope multiplied by the hundreds of feet per min- 
ute traveled. (L. I. Seymour.) 

Breaking strength of manila rope in pounds = C 2 x coefficient. The 
coefficient varies from 900 for J-inch to 700 for 2-inch diameter rope. The 
following is a reliable table prepared by T. Spencer Miller, M.E. (See En- 
gineering News, December 6, 1890.) 



Diameter. 


Circumference. 


Ultimate Strength. 


Coefficient. 


i 


U 


2,000 


900 




2 


3,250 


845 


J 


2i; 


4,000 


820 


i 


2| 


6,000 


790 


1 


3 


7,000 


780 


1* 


3i 


9,350 


765 


li 


3f 


10,000 


760 


If 


41 


13,500 


745 


1* 


4* 


15,000 


735 


If 


5 


18,200 


725 


If 


H 


21,750 


712 


2 


6 


25,000 


700 



This table was compiled by averaging and graduating results of tests at 
the Watertown Arsenal and Laboratory of Rieble Brothers, in Philadelphia. 

Weight of manila rope in pounds per foot r= .032 (Circumference in 
inches) 2 . (C. W. Hunt.) 

or, diameter of rope in inches squared = weight in pounds per yard ap- 
proximately. 

The coefficient of friction on a rope working on a cast-iron pulley = 0.28 ; 
when working in an ungreased groove it is increased about three times, or 
from 0.57 to 0.84. If the pulleys are greased, the coefficient is reduced 
about one-half. It has been found by experiment that a rope 6 inches cir- 
cumference in a grooved pulley possesses four times the adhesive resistance 
to slipping, exhibited by a half -worn, ungreased 4-inch single belt. 

The length of splice should be 72 times the diameter of rope. The strength 
of a rope containing a properly made " long splice" was found to be 7,000 
pounds per square inch of section. 

A mixture of molasses and plumbago makes an excellent dope for trans- 
mitting ropes. Grease and oils of all kinds should be kept from transmis- 
sion ropes, since, as a rule, they are injurious. 

Following is another formula for horse-power of manila rope : 



H.P. 



. (T -QV 
33000 ' 



J n which h.p. is the horse-power transmitted by one rope, Uthe velocity in 
feet per minute, T the maximum working stress, and Cthe centrifugal 
tension, so that (T — C) is the net tension available for the transmission of 
power. Taking the total maximum stress at 200d 2 and allow 20 % of this 

for slack side tension, we have T = 160<7 2 , so that H.P. =- ' • 

oo ,U0u 

A table has been calculated by this rule, giving the horse-power per rope, 
transmitted at various speeds. 



ROPE DRIVING. 



955 



C= Centrifugal Tension in Manila Ropes — Pounds. 



ocity 
Rope 
t. per 








Nominal Diameter of Rope 


n Inches. 






CD , tf - 1 -rt 


2 


f 


1 


I 


1 


1* 


U 


If 


li If 


If 


2 


1000 


0.7 


1.1 


1.5 


2.1 


2.7 


3.4 


4.3 


5.1 


6.2 


7.2 


8.3 


11 


1500 


1.5 


2.4 


3.4 


4.7 


6.2 


7.6 


9.7 


11 


13 


16 


18 


25 


2000 


2.7 


4.3 


6.1 


8.2 


11 


13 


17 


20 


24 


28 


33 


44 


2500 


4.3 


6.7 


9.6 


13 


17 


21 


27 


32 


38 


45 


52 


69 


3000 


6.2 


9.7 


13 


18 


24 


30 


39 


45 


55 


64 


74 


100 


3500 


8.4 


13 


19 


25 


34 


42 


53 


63 


75 


89 


102 


136 


4000 


11 


17 


24 


33 


44 


54 


69 


82 


98 


116 


133 


177 


4500 


14 


22 


31 


42 


55 


69 


87 


103 


125 


146 


168 


223 


5000 


17 


27 


39 


52 


69 


86 


109 


129 


156 


183 


210 


275 


• 5500 


21 


33 


47 


63 


83 


104 


132 


156 


189 


221 


254 


332 


6000 


24 


39 


56 


75 


99 


125 


157 


188 


225 


257 


303 


396 


6500 


39 


45 


65 


88 


116 


145 


183 


217 


261 


307 


353 


462 



Horse-Power of Manila, Ropes. 



•H&S 






Nominal 


Diameter of Rope in 


Inches. 






Velc 
of R 
Ft. 
Min 


A 


f 


1 


i 


1 


H 


11 


If 


li 


If 


If 


2 


2000 


2.25 


3.51 


5.14 


6.84 


9.08 


11.5 


14.0 


17.0 


20.3 


23.8 


27.5 


36.1 


2100 


2.35 


3.67 


5.27 


7.15 


9.40 


11.8 


14.7 


17.8 


21.1 


24.8 


28.8 


37.6 


2200 


2.45 


3.82 


5.48 


7.45 


9.80 


12.3 


15.3 


18.5 


22.0 


25.9 


30.0 


39.2 


2300 


2.55 


3.98 


5.71 


7.75 


10.2 


12.8 


15.9 


19.3 


22.9 


26.9 


31.2 


40.8 


2400 


2.62 


4.10 


5.89 


7.98 


10.5 


13.2 


16.4 


19.8 


23.6 


27.7 


32.2 


42.0 


2500 


2.70 


4.21 


6.05 


8.21 


10.8 


13.6 


16.8 


20.4 


24.3 


28.5 


33.1 


43.2 


2600 


2.78 


4.33 


6.21 


8.43 


11.1 


14.0 


17.3 


21.0 


25.0 


29.3 


34.0 


44.4 


2700 


2.85 


4.45 


6.39 


8.67 


11.4 


14.4 


17.8 


21.5 


25.6 


30.5 


35.0 


45.6 


2800 


2.94 


4.59 


6.59 


8.93 


11.75 


14.8 


18.3 


22.2 


26.4 


31.0 


36.0 


47.0 


2900 


3.00 


4.68 


6.73 


9.13 


12.0 


15.1 


18.7 


22.7 


27.0 


31.6 


36.8 


48.0 


3000 


3.06 


4.78 


6.87 


9.32 


12.3 


15.4 


19.1 


23.2 


27.6 


32.3 


37.6 


49.1 


3100 


3.12 


4.87 


7.01 


9.50 


12.5 


15.7 


19.5 


23.6 


28.2 


33.0 


38.3 


50.0 


3200 


3.18 


4.97 


7.14 


9.70 


12.7 


16.0 


19.9 


24.0 


28.7 


33.7 


39.0 


51.0 


3300 


3.25 


5.07 


7.27 


9.89 


13.0 


16.3 


20.3 


24.5 


29.2 


34.3 


39.8 


52.0 


3400 


3.30 


5.15 


7.39 


10.0 


13.2 


16.6 


20.6 


25.0 


29.7 


34.8 


40.4 


52.8 


3500 


3.35 


5.22 


7.50 


10.2 


13.4 


16.9 


20.9 


25.3 


30.1 


35.4 


41.0 


53.6 


3600 


3.40 


5.30 


7.61 


10.3 


13.6 


17.1 


21.2 


25.7 


30.6 


35.9 


41.6 


54.4 


3700 


3.44 


5.36 


7.70 


10.4 


13.7 


17.3 


21.5 


26.0 


30.0 


36.3 


42.1 


55.0 


3800 


3.46 


5.40 


7.76 


10.5 


13.8 


17.4 


21.6 


26.2 


31.1 


36.6 


42.4 


55.4 


3900 


3.49 


5.45 


7.81 


10.6 


13.9 


17.6 


21.8 


26.4 


31.4 


36.9 


42.7 


55.8 


4000 


3.51 


5.49 


7.86 


10.6 


14.0 


17.7 


21.9 


26.5 


31.6 


37.1 


43.0 


56.1 


4100 


3.53 


5.52 


7.92 


10.7 


14.1 


17.8 


22.0 


26.7 


31.8 


37.3 


43.2 


56.4 


4200 


3.55 


5.54 


7.95 


10.8 


14.2 


17.9 


22.1 


26.8 


31.9 


37.5 


43.4 


56.8 


4300 


3.56 


5.55 


7.98 


10.8 


14.2 


17.9 


22.2 


26.9 


32.0 


37.6 


43.6 


56.9 


4400 


3.57 


5.56 


7.99 


10.8 


14.2 


18.0 


22.2 


27.0 


32.1 


37.6 


43.6 


57.0 


4500 


3.56 


5.55 


7.96 


10.8 


14.2 


17.9 


22.2 


26.9 


32.0 


37.6 


43.5 


56.9 


4600 


3.55 


5.54 


7-95 


10.8 


14.2 


17.9 


22.1 


26.8 


31.9 


37.5 


43.4 


56.8 


4700 


3.53 


5.50 


7.90 


10.7 


14.1 


17.8 


22.0 


26.6 


31.7 


37.2 


43.1 


56.4 


4800 


3.51 


5.48 


7.S6 


10.7 


14.0 


17.7 


21.9 


26.5 


31.6 


37.1 


43.0 


56.2 


4900 


3.49 


5.45 


7.81 


10.6 


13.9 


17.6 


21.8 


26.4 


31.4 


36.9 


42.7 


55.8 


5000 


3.45 


5.38 


7.73 


10.5 


13.8 


17.4 


21.5 


26.1 


31.0 


36.4 


42.2 


55.2 


5100 


3.43 


5.35 


7.67 


10.4 


13.7 


17.2 


21.3 


25.9 


30.8 


36.2 


41.9 


54.8 


5200 


3.38 


5.26 


V.56 


10.2 


13.5 


17.0 


21.0 


25.5 


30.4 


35.6 


41.3 


54.0 


5300 


3.34 


5.20 


7.47 


10.1 


13.3 


16.8 


20.8 


25.2 


30.0 


35.2 


40.8 


53.4 


5400 


3.28 


5.11 


7.34 


9.95 


13.1 


16.5 


20.4 


24.8 


29.4 


34.6 


40.1 


52.5 


5500 


3.21 


5.00 


7.20 


9.75 


12.8 


16.2 


20.0 


24.2 


28.9 


33.9 


39.3 


51.4 


6000 


2.78 


4.33 


6.21 


8.43 


11.1 


14.0 


17.3 


21.0 


25.0 


29.3 


34.0 


44.4 


6500 


2.17 


3.38 


4.S5 


6.60 


8.6 


10.9 


13.5 


16.4 


19.5 


22.9 


26.5 


34.7 



956 



SHAFTING, PULLEYS, BELTING, ETC. 



HORSE POWER 



CJ <M t-i th r-t t-4 r-l 



-^4& 




^f 


S^ /' / / 


S^ / / / 


s 7 * ^ / / 


S* / _T _J~ 


y^ / * 7 


/' / l 4 


A / it 


4 -4 -t t- 


1-4 -t 


1 t 


i- Jr - f 


v ■■ ■ i \ l 


\ -K- i a - 


\ V V 3 


\ V ^ i - 


\ s i X 


K \ \ V \ 


E X \ \ \ 


O -J q V \ \ \ 


£< " X X N \ 


Q ° o \> \ \ V- 


s H • "t 15 S 


2 i s *&$$$ 




8 \\\ 


H 



8 o 



<SJ O 00 O 



Fig. 21. 



ROPE DRIVING. 



957 



Horse-Power of " Stevedore " Transmission Rope at 
Various Speeds. 

In this table the effect of the centrifugal force has been taken into con- 
sideration, and the strain on the fibers of the rope is the same at all 
speeds when transmitting the horse-power given in the table. When more 
than one rope is used, multiply the tabular number by the number of the 
ropes. At a speed of 8,400 per minute the centrifugal force absorbs all the 
allowable tension the rope should bear, and no power will be transmitted. 

Table of the Horse-Power of Transmission Rope. 

(Hunt's Formula.) 



o 

u 

S c 
.£# 


Speed of the Rope in Feet per Minute. 


3^ 


1,500 


2,000 


2,500 


3,000 


3,500 


4,000 


4,500 


5,000 


6,000 


7,000 


8,400 


12 


i 


1.45 


1.9 


2.3 


2.7 


3. 


3.2 


3.4 


3.4 


3.1 


2.2 


.0 


.20 


f 


2.3 


3.2 


3.6 


4.2 


4.6 


5.0 


5.3 


5.3 


4.9 


3.4 


.0 


.25 


1 


3.3 


4.3 


5.2 


5.8 


6.7 


7.2 


7.7 


7.7 


7.1 


4.9 


.0 


.30 


i 


4.5 


5.9 


7.0 


8.2 


9.1 


9.8 


10.8 


10.7 


9.3 


6.9 


.0 


.36 


l 


5.8 


7.7 


9.2 


10.7 


11.9 


12.8 


13.6 


13.7 


12.5 


8.8 


.0 


.42 


U 


9.2 


12.1 


14.3 


16.8 


18.6 


20.0 


21.2 


21.4 


19.5 


13.8 


.0 


.54 


l* 


13.1 


17.4 


20.7 


23.1 


26.8 


28.8 


30.6 


30.8 


28.2 


19.8 


.0 


.60 


11 


18. 


23.7 


28.2 


32.8 


36.4 


39.2 


41.5 


41.8 


37.4 


27.6 


.0 


.72 


2 


23.2 


30.8 


36.8 


42.8 . 


47.6 


51.2 


54.4 


54.8 


50. 


35.2 


.0 


.84 



For a temporary installation when the rope is not to be long in use, it 
might be advisable to increase the work to double that given in the tables. 

Slip of Ropes and Relts. 

(W. W. Christie.) 
Some French trials, with constant resistance, the power expended and 
slip in several modes of transmission was as follows : 

Ropes, 158.54 gross h.p., Slip, 0.33 per cent. 

Cotton belt, 159.67 " " 0.78 " 

Leather " 158.84 " " 0.96 " 

" " 160.23 " " 0.78 " 

Stated in percentage value, the results were : 

Ropes, 100.00 gross power, Slip, 0.100. 

Cotton belt, 100.87 " " 0.237. 

Leather " 100.37 " " 0.292. 

" 101.07 " " 0.237. 



958 



SHAFTING, PULLEYS, BELTING, ETC. 



Manila Cordage. 


Tarred 
Hemp. 


Size, Cir- 


Size, 


Weight of 


Feet in 


Breaking Strain 


Weight of 


cumfer'ce. 


Diameter. 


100 


one 


of New Bopes. 


100 


Inches. 


Inches. 


Fathoms. 


Pound. 


Pounds. 


Fathoms. 










For Bo pes in use 




li 


3 

f 


31 


20 


deduct ^ from 


40 


1* 


44 


14 


these figures, for 


55 


If 




60 


10 


chafing, etc. 


75 


2 


1 


79 


n 


3000 


100 


2i 


1 


99 


6 


4000 


125 


2| 


if 


122 


5 


5000 


155 


2| 


1 


146 


4 


6000 


190 


3 




176 


3| 


7000 


225 


3i 


if 


207 


3 


8500 


265 


3£ 


240 


2h 


9500 


300 


3| 


H 


275 


2i 


11000 


355 


4 


l-^ 


305 




12500 


405 


4i 




355 


1& 


14000 


455 


4* 


i* 


395 


it 


16000 


500 


5 


if 


490 


20000 


630 


5| 




595 


1 


24000 


750 


6 


2 


705 


10 in. 


27000 


910 


6i 


2& 


825 


7* 
6? 


31500 


1050 


7 


2i 


960 


37000 


1235 


7£ 


% 


1100 


42500 


1400 


8 


2f 


1255 


5£ 


4850o 


1600 


si 


21 


1415 


5 


54500 


1820 


9 


3 


1585 


4J 


61500 


2050 



Hawser laid will weigh £ less. 
Notes on the Uses of Wive Rope. 

(Boebling.) 

Two kinds of wire rope are manufactured. The most pliable variety con- 
tains 19 wires in the strand, and is generally used for hoisting and running 
rope. 

For safe working load allow ^ or \ of the ultimate strength, according to 
speed, so as to get good wear from the rope. Wire rope is as pliable as new 
hemp rope of the same strength ; but the greater the diameter of the 
sheaves the longer wire rope will last. 

Experience has proved that the wear increases with the speed. It is, 
therefore, better to increase the load than the speed. Wire rope must not 
be coiled or uncoiled like hemp or manila — all untwisting or kinking must 
be avoided. 

In no case should galvanized rope be used for running. One day's use 
scrapes off the zinc coating. 



Table of Strains Produced by 


Loads on Inclined Planes. 




Strain in Lbs. on 


Elevation in 
100 Ft. 


Strain in Lbs. on 


Elevation in 100 Ft. 


Bope from a Load 


Bope from a Load 




of 1 Ton. 


of 1 Ton. 


Ft. Deg. 




Ft. Deg. 




10= bh 


212 


90 = 42 


1347 


20 = 1H 


404 


100 = 45 


1419 


30 = 16J 


586 


110 = 47| 


1487 


40 = 21| 


754 


120 = 5Q\ 


1544 


50 = 26J 


905 


130 = 52^ 


1592 


60 = 31 


1040 


140 = 54i 


1633 


70 = 35 


1156 


150 = 56i 


1671 


80 = 38§ 


1260 


160 = 58 


1703 I 



ROPE DRIVING. 



959 



Table of Transmission of Power l»y Wire Hopes. 

Showing necessary size and speed of wheels and rope to obtain any de- 
sired amount of power. 

(Roebling.) 



Diam. 








Diam. 








of 


No. of Rev- 


of 
Rope. 


Horse- 


of 


No. of Rev- 


of 
Rope. 


Horse- 


Wheel 
in Ft. 


olutions. 


Power. 


Wheel 
in Ft. 


olutions. 


Power. 


4 


80 


| 


3.3 


10 


80 


H 


58.4 




100 


1 


4.1 




100 


» 


73. 




120 


f 


5. 




120 




87.6 




140 


5.8 




140 


T5 


102.2 


5 


80 


T 7 6 


6.9 


11 


80 


H 


75.5 




100 


T 7 B 


8.6 




100 


14 


94.4 




120 


ft 


10.3 




120 




113.3 




140 


ft 


12.1 




140 


1* 


132.1 


6 


80 


i 


10.7 


12 


80 


i 


99.3 




100 


h 


13.4 




100 


124.1 




120 


I 


16.1 




120 


i 


148.9 




140 


18.7 




140 


t 


173.7 


7 


80 




16.9 


13 


80 


I 


122.6 




100 


1 9 6 


21.1 




100 


! 


153.2 




120 


A 


25.3 




120 


183.9 


8 


80 


§ 


22. 


14 


80 


i 


148. 




100 


f 


27.5 




100 


7 


185. 




120 


f 


33. 




120 


1 


222. 


9 


80 


| 


41.5 


15 


80 


| 


217. 




100 


f 


51.9 




100 


i 


259. 




120 


s 


62.2 




120 


i 


300. 



Hoisting- Hopes (19 Wires to the Strand). 

(Trenton Iron Company's List.) 



Iron. 


Crucible Steel. 


s 


fl 


05 

a? 


•SMS 


-CS =4-1 


%*2 


•a. 


S 




oH,o 


® 8, 

ojPh 


N O jj 

33 g fe 


3 

05 ■ 

H 


3 
2 


3 fl 


■?°3 

^ o . 
ceH as 

05 _,Q 


n o o 

031-3 to . 


05 ft^r^ 

a S Ebb 
S 05 a*3 

J. 14-1 t*-l *a 

•50OCG 


03 Jj" _ 

N O J, 

%£% 

• 05 


CO ° » 

w- Seq 


n -8 

05 -Co 
*-i J O 


05 Oh-^5 
H 05 (j<pl 


1 


2i 


7 


8. 


74 


15 


15* 


8 


164.69 


32.9 




9 


2 


2 


S 


6.3 


65 


13 


14 


7 


132.37 


26.5 




8 


3 


1* 


5.25 


54 


11 


13 


6* 


108.13 


21.63 




7* 


4 


*t 


5 


4.1 


44 


9 


12 


5 


97.17 


19.44 




6 


5 


H 


4* 


3.65 


39 


8 


11* 

10i 


4f 


86.38 


17.3 


16* 


5* 


b* 


is 


4± 


3. 


33 


6.5 


4* 


61.00 


12.2 


15 


5 


6 


2 t 


4 


2.5 


27 


5.5 


9* 


4 


50.17 


10. 


12J 


5 


V 


i* 


Sh 


2. 


20 


4 


8 


3* 


38.00 


7.7 


11 


4* 


8 


l 


•^ 


1.58 


16 


3 


7 


3 


29.2 


5.8 


9 


4 


9 


1 

4 


2f 


1.2 


11.5 


2.5 


6 


2f 


21.55 


4. 


8 


1 


10 


2* 


.88 


8.64 


1.75 


5 


2* 


14.99 


3. 


6* 


10i 


* 


2 


.7 


5.13 


1.25 


4* 


2 


12.53 


2.5 


5f 


3 


10i 


f 


1* 


.44 


4.27 


.75 


4 


If 


8.81 


1.75 


5* 


2f 


io| 


u 


.35 


3.48 


.5 


3* 


1* 


7.62 


1.5 


4| 


2 



960 



SHAFTING, PULLEYS, BELTING, ETC. 



The drums and sheaves should be made as large as possible. The mini- 
mum size of drum is given in a column in table. 

It is better to increase the load than the speed. 

Wire rope is manufactured either with a wire or a hemp center. The 
latter is more pliable than the former, and will wear better where there is 
short bending. The weight of rope with wire center is about 10 per cent 
more than with hemp center. 

Power Transmission and Standing- Ropes (7 Wires to 
the Strand). 

(Trenton Iron Company's List.) 



Iron. 


Crucible Steel. 










5 02 


<tH 




a 03 


*-( 








a 




1.0 


o 


*£ & 


^ 


t «o 


'*->, -a' 


u 

£ 

•a 

cS 

u 


da 

a 


a 

03 


53 ^ S3 


0Q§1 


a 2 

■2h 


a; O bjD 
© © a 

a a,£ 

«o5 


8^ 


bJ0 M 

.2 a 


« <d a 
a a * 




S . 

2 G 


■SHg 


«e o 


2^° 


111 


a° 
3 a 


a<oS 


gg 1 * 

? 53 & 


H 


fi 


6 


M 


Ah 


b 


w 


^ 


b 


11 


l* 


4f 


3.37 


36 


9 


lOf 


88.38 


22 


16i 


12 


if 


*i 


2.77 


30 


7* 


10 


67.2 


16.8 


15$ 


13 


11 


4 


2.28 


25 


6i 


9i 


60.67 


15.2 


15 


14 


l* 


3| 


1.82 


20 


5 


8 


39.84 


10. 


11 


15 


l 


i 


1.5 


16 


4 


7 


31.82 


8. 


9* 


16 


£ 


1.12 


12.3 


3 


si 


24.7 


6.2 


8* 


17 


j 


2| 


.88 


8.8 


21 


18.48 


4.6 


7| 


18 


1 1 

F 


2i 


.7 


7.6 


2 


5 


16.32 


4. 


71 


19 


2 


.57 


5.8 


1* 


*t 


12.44 


3.1 


6 


20 


f 


If 


.41 


4.1 


1 


4 


9.33 


2.3 


51 


21 


1* 


.31 


2.83 


| 


34 


6.89 


1.7 


4* 


22 


A 


l| 


.23 


2.13 


03 

3 


5.23 


1.3 


3£ 


23 


| 


H 


.19 


1.65 




3.93 


1. 


3i 


24 


TB 


l 


.16 


1.38 




4 


3.25 


.81 


3 


25 


A 


f 


.125 


1.03 




2 


2.96 


.75 


2f 



IVire Rope. 

Tons breaking weight = (diameter in quarter inches) 2 . 



MISCELLANEOUS TABLES. 



WEIGHTS .WD MEASrHES. 
Measure of Capacity. 

Gallon. — The standard gallon measures 231 cubic inches, and contains 
8.3388822 pounds avoirdupois = 58372.1757 grains Troy, of distilled water, at 
its maximum density 39.83° Fahrenheit, and 30 inches barometer height. 

Bushel. —The standard bushel measures 2150.42 cubic inches —77.627413 
pounds avoirdupois of distilled water at 39.83° Fahrenheit, barometer 30 
inches. Its dimensions are 18£ inches inside diameter, 19£ inches outside, 
and 8 inches deep ; and when heaped, the cone must not be less than 6 
inches high, equal 2747.70 cubic inches for a true cone. 

Pound.- The standard pound avoirdupois is the weight of 27.7015 cubic 
inches of distilled water, at 39.83° Fahrenheit, barometer 30 inches, and 
weighed in the air. 

measure of I>eiig-th. 



Miles. 


Furlongs. 


Chains. 


Rods. 


Yards. 


Feet. 


Inches. 


1 


8 


80 


320 


1760 


5280 


63360 


0.125 


1 


10 


40 


220 


660 


7920 


0.0125 


0.1 


1 


4 


22 


66 


792 


0.003125 


0.025 


0.25 


1 


5.5 


16.5 


198 


0.00056818 


0.0045454 


0.045454 


0.181818 


1 


3 


36 


0.00018939 


0.00151515 


0.01515151 


0.0606060 


0.33333 


1 


12 


0.000015783 


0.000126262 


0.001262626 


0.00505050 


0.0277777 


0.083333 


1 



Measure of Surface. 



Sq. Miles. 


Acres. 


S. Chains 


Sq. Rods. 


Sq. Yards 


Sq. Feet. 


Sq. Inches 


1 


640 


6400 


102400 


3097600 


27878400 


4014489600 


0-001562 


1 


10 


160 


4840 


43560 


6272640 


0.0001562 


0.1 


1 


16 


484 


4356 


627264 


0.000009764 


0.00625 


0.0625 


1 


30.25 


272.25 


39204 


0.000000323 


0.0002066 


0.002066 


0.0330 


1 


9 


1296 


0.0000000358 


0.00002296 


0.0002296 


0.00367 


0.1111111 


1 


144 


0.00000000025 


0.000000159 


0.00000159 


0.00002552 


0.0007716 


0.006944 


1 



Measure of Capacity. 



Cub. Yard. 


Bushel. 


Cub. Feet. 


Pecks. 


Gallons. 


Cub. Inch. 


1 


21.6962 


27 


100.987 


201.974 


46656 


0.03961 


1 


1.24445 


4 


9.30918 


2150.42 


0.037037 


0.803564 


1 


3.21425 


7.4805 


1728 


0.009259 


0.25 


0.31114 


1 


2.32729 


537.605 





0.107421 


0.133681 


0.429684 


1 


231 








0.000547 


0.001860 


0.004329 


1 



901 



962 



MISCELLANEOUS TABLES. 



Measure of liquids. 



Gallon. 


Quarts. 


Pints. 


Gills. 


Cub. Inch. 


X 
0.25 
0.125 
0.03125 
0.004329 


4 

X 
0.5 
0.125 
0.17315 


8 

2 
X 
0.25 
0.03463 


32 

8 

4 

X 

0.13858 


231 
57.75 

28.875 
7.21875 

X 



measures of lVeig-lits. 

AVOIRDUPOIS. 



Ton. 


Cwt. 


Pounds. 


Ounces. 


Drams. 


X 


20 


2240 


35840 


573440 


0.05 


X 


112 


1792 


28672 


0.00044642 


0.0089285 


X 


16 


256 


0.00002790 


0.000558 


0.0625 


X 


16 


0.00000174 


0.0000348 


0.0016 


0.0625 


X 



APOTHECARIES. 



Pounds. 


Ounces. 


Dwt. 


Grains. 


Pound Avoir. 


X 
0.083333 
0.004166 
0.0001736 
1.215275 


12 
X 

0.05000 

0.002083333 

14.58333 


240 
20 

0.0416666 
291.6666 


5760 

480 

24 

X 

7000 


0.822861 
0.068571 
0.0034285 
0.00014285 

X 



Pounds. 


Ounces. 


Drams. 


Scruples. 


X 
0.08333 
0.01041666 
0.0034722 
0.00017361 


12 

X 
0.125 
0.0416666 
0.0020833 


96 
8 

X 
0.3333 
0.016666 


288 

24 

3 

X 

0.05 



Grains. 
5760 



Equivalents of JLiueal Pleasures — Metrical and Kng-lisli. 









English Measures. 




















Inches. 


Feet. 


Yards. 


Miles, 


Microne .... 


.0001 


.003937 


.000328 


.000109 




Millimeter . . mm 


.001 


.039371 


.003281 


.001094 




Centimeter . cm 


.01 


.393708 


.032809 


.010936 




Decimeter . . . 


.1 


3.937079 


.328089 


.109363 




Meter 


1. 


39.370790 


3.280899 


1.093633 


.000621 


Decameter . . 


10. 




32.80899 


10.93633 


.006214 


Hectometer . . 


100. 




328.0899 


109.3633 


.062138 


Kilometer . . . 


1,000. 




3280.899 


1093.633 


.621382 


Miriameter . . 


10,000. 








6.213824 



_ 



MISCELLANEOUS TABLES. 



963 



Equivalents of Eineal measures — Met. and Xing'. — Continued. 



English Measures. 



1 inch 

12 inches = 1 foot 

3 feet = 1 yard 

5J yards=16£ f eefczrl rod or pole 

4 poles = 66 feet = 22 yards = 1 chain (Gunter's) 
80 chains = 320 poles = 5280 ft.= 1760 yds.=rlmile 



Meters. 



.02539954 
.3047945 
.9143835 
5.029109 
20.11644 
1609.3149 



Reciprocals. 



39.37079 
3.280899 
1.093633 
.1988424 
.0497106 
.00062138 



A Gunter's chain has 100 links. Each link = 7.92 inches = 0.2017 meter. 



Equivalent's of Superficial Measures — Metrical and 

(METRICAL, AND ENGLISH MEASURES.) 



Xing'. 





Square 
meters. 


English Measures. 




Square 
inches. 


Square 
feet. 


Square 
yards. 


Acres. 


Square 
miles. 


Milliare . . . 
Centiare=sq.met 
Deciare . . . 

Are 

Decare (not used) 
Hectare . . . 
Square kilometer 


.1 
1. 
10. 
100. 

1000. 

10000. 

1000000. 


155.01 
1550.06 
15500.59 
155005.9 


1.076 
10.764 
107.64 
1076.4 
10764.3 
107643. 


.119 

1.196 

11.960 

119.6033 

1196.033 

11960.33 


2.4711431 
247.11431 


.386126 


English Measures. 


Metrical Measures. 


Reciprocals. 




6.451367 sq. cent. 
.09289968 sq.mt. 
.8360972 " " 

25.29194 " " 


.1550059 


144 square inches 

9 square feet rr 1 
30i sq. yds. ) _ 1 p 
272J sq. ft. J — or 
160 perches = ) _ 

10 sq. chains ) 
640 acres = 1 squa 


= 1 square foot . 
square yard . . 
erch = 1 square rod 

pole 


10.7642996 
1.196033 

.0395383 


re mile .... 


4046.71 

2589894.5 


1 




.00024711 
.00000038612 



Equivalents of Weights 


— Metrical and English. 




Grammes 


English Weights. 




Oz. 

avoir. 


Lbs. 

avoir. 


Tons 
2000 lbs. 


Tons 
2240 lbs. 


Troy 
weight. 


Milligramme . 
Centigramme . 
Decigramme . 
Gramme . . . 
Decagramme . 
Hectogramme . 
Kilogramme . 
Myriagramme . 
Quintal . . . 
Millier or Tonne 


.001 
.01 
.1 
1. 

10. 

100. 

1000. 

10000. 

100000. 

1000000 


' .0353 

.3527 

3.5274 

35.2739 

352.7394 

3527.3943 


' .0022 

.02205 

.22046 

2.2046 

22.0462 

220.4261 

2204.6215 


.001102 

.011023 

.110231 

1.102311 


.000984 
.009842 
.098421 
.984206 


.015 Grs. 
.15 " 
1.543 " 
15.43235" 

. . . . oz. 

32.150727" 

321.507266" 

3215.07266 " 

32150.72655" 


English Weights — " Avoirdupois." 


Grammes. 


Reciprocals. 




.06479895 
1.771836 
28.349375 
453.592652 
45359.265 
50802.376 
907.18524 
1016.04753 

.06479895 
1.555175 
31.103496 
373.241954 


15 43234875 


24.34375 grains = 1 dram 
16 drams = 1 ounce = 437.5 
16 ounces = 1 pound = 7000 
100 lbs. =: 1 cwt. (American 
112 lbs. = 1 cwt. (English) . 
20 cwt. = 1 ton (Am.) in kil 
20 cwt. = 1 ton (Eng.) in ki 
English Weights — " T 






.564383 


grains 
grains 
) . . . . 




.0352739 
.00220462 
.000022046 
.00001968 






001102311 


OS . . . 
roy." 




.000984206 
15 43234875 


24 grains = 1 dw 
20 dwt — 1 oz. 


t 




6430146 






.3215073 


12 oz. — 1 lb 


nn9fi7Q93 















964 



MISCELLANEOUS TABLES. 



m H 
I* 
I H 

*£ 

a - 

8 ° 

» e 

"SI 

9 



— v 



W§ 



cS <M 

On 



02,2-g 

t> cS o 



o£ 



:§i! 



~28 



CI N LO ^ « o 
o «M I- io >-i c-i 



i c c r. 

IT) C O 



IO-H — 1 



o n o ■* h o cj 

— i o ?i -o *# H t~ 

i o o « v > o -* 1 1- 1 



f*SC1 t- 00 

•lOMHt-LO 

,«sio«hio 

'©COiOMrt 



8 • 



<X> T- © £» £- O 

SO Si 



'S8 



-S8§8 

rnpo 



"3 ■ • a 

© • .'3 



6 



2* 



3sS £ * 



.- CO 
e 



® £ © ?H oj h 
£ *=> ^ ' 5 55 u 55 

3 "§ '© 2 © « 2 : b 

• H Si tl-S « «-h ^> 



<m oo 23 — — 

OCOCONNON OS 

o»«ooo5h«n 

• • • SO 00 CO tO Ol i-l O 

S"t-»fINOiOO 



lO CO t- I 

1-icoioooo-jhc^wi 

CO 00 £h t~ I?} CO Ut> t~ < 

xcnifflwtooTfi 





3 


> i 


© 

© 

|3 
© 

-+< 

t» 

Ml 3 




a 

c 
p 

-i 

s 


* 
> 



=2 3 3^© 

2 £ ©3'E- 1 
© © >>>,£ s 

■^J 'O -Q 
%■■-<% CUT* ||^ 

.g.S'H £ I, 11-3 
.2=*;3X2'S © 

Soo 553 53 3-- 
©g^ aaa'^ 

HHOHj;r)lH 






00 00 



MISCELLANEOUS TABLES. 965 

metrical measures Equivalent to English Measures. 



Meters. 


Inches. 


Feet. 


l m /m 


0.039 


0.0033 


2 


0.079 


0.0066 


3 


0.118 


0.0098 


4 


0.157 


0.0131 


5 


0.197 


0.0164 


6 


0.236 


0.0197 


7 


0.276 


0.0230 


8 


0.315 


0.0262 


9 


0.354 


0.0295 


10">/ m = l«/m 


0.394 


0.033 


2 


0.787 


0.066 


3 


1.181 


0.098 


4 


1.575 


0.131 


5 


1.969 


0.164 


6 


2.362 


0.197 


7 


2.756 


0.230 


8 


3.150 


0.262 


9 


3.543 


0.295 


10c/m = .l m 


3.937 


0.328 


.2 


7.874 


0.656 


•3 


11.811 


0.984 


.4 


15.748 


1.312 


.5 


19.685 


1.64G 


.6 


23.622 


1.969 


.7 


27.560 


2.297 


.8 


31.497 


2.625 


.9 


35.434 


2953 


l m 


39.371 


3.281 



Table for the Conversion of Mils. (I-IOOO Inches) 
Centimeters. 



into 





Centi- 




Centi- 




Centi- 




Centi- 


Mils. 


meters. 


Mils. 


meters. 


Mils. 


meters. 


Mils. 


meters. 


1 


.00254 


18 


.04571 


35 


.08888 


52 


.1321 


2 


.00508 


19 


.•04825 


36 


.09142 


53 


.1346 


3 


.00762 


20 


.05079 


37 


.09396 


54 


.1372 


4 


.01016 


21 


.05333 


38 


.09650 


55 


.1397 


5 


.01270 


22 


.05587 


39 


.09904 


56 


.1422 


6 


.01524 


23 


.05841 


40 


.1016 


57 


.1448 


7 


.01778 


24 


.06095 


41 


.1041 


58 


.1473 


8 


.02032 


25 


.06348 


42 


.1067 


59 


.1499 


9 


.02286 


26 


.06602 


43 


.1092 


60 


.1524 


10 


.02540 


27 


.06856 


44 


.1118 


61 


.1549 


11 


.02793 


28 


.07110 


45 


.1143 


62 


.1575 


12 


.03047 


29 


.07364 


46 


.1168 


63 


.16(10 


13 


.03301 


30 


.07618 


47 


.1194 


64 


.1626 


14 


.03555 


31 


.07872 


48 


•1219 


65 


.1651 


15 


.03809 


32 


.08126 


49 


.1245 


66 


.1676 


16 


.04063 


33 


.08380 


50 


.1270 


67 


.1702 


17 


.04317 


34 


.08634 


51 


.1295 


68 


.1727 



966 MISCELLANEOUS TABLES. 

Table for the Conversion of Mils. — Continued. 





Centi- 




Centi- 




Centi- 




Centi- 


Mils. 


meters. 


Mils. 


meters. 


Mils. 


meters. 


Mils. 


meters. 


69 


.1752 


77 


.1956 


85 


.2159 


93 


.•2362 


70 


.1778 


78 


.1981 


86 


.2184 


94 


.2387 


71 


.1803 


79 


.2006 


87 


.2209 


95 


.2413 


72 


.1829 


80 


.2032 


88 


.2235 


96 


.2438 


73 


.1854 


81 


.2057 


89 


.2260 


97 


.2465 


74 


.1879 


82 


.2083 


90 


.2286 


98 


.2489 


75 


.1905 


83 


.2108 


91 


.2311 


99 


.2514 


76 


.1930 


84 


.2133 


92 


.2336 


100 


.2540 



English Measures Equivalent to Metrical Measures. 









1 








CO 




i-l 




u 










CO 
CP 


CD 
CD 


"3 


CD 
CP 


Eh 


CD 


CD 
CP 


<D 


1=1 


l 














A 


0.794 


1 


0.0254 


0.01 


.003 


10 


3.048 


TB 


1.588 


2 


.0508 


0.02 


.006 


20 


6.096 


f 


2.381 


3 


.0762 


0.03 


.009 


30 


9.144 


3.175 


4 


.1016 


0.04 


.012 


40 


12.192 


f 

SIS 


3.969 


5 


.1270 


0.05 


.015 


50 


15.240 


4.762 


6 


.1524 


0.06 


.018 


60 


18.288 


5.556 


7 


.1778 


0.07 


.021 


70 


21.336 


6.350 


8 


.2032 


0.08 


.024 


80 


24.384 


7.144 


9 


.2286 


0.09 


.027 


90 


27.431 


7.937 


10 


.2540 


.1 


.030 


100 


30.479 


T5 

f 

if 

T 7 = 


8.731 


11 


.2794 


.2 


.061 


200 


60.959 


9.525 


12 


.3048 


.3 


.091 


300 


91.438 


10.319 






.4 


.122 


400 


121.918 


11 112 






.5 


.152 


500 


152.397 


f 


11 906 






.6 


.183 


600 


182.877 


12.700 
13.494 






.7 
.8 
.9 


.213 
.244 
.274 


700 
800 
900 


213.356 
243.836 
274.315 


IB 

f 


14.287 
15.081 
15.875 
16.668 






1.0 
2 
3 
4 


.305 

.610 

.914 

1.219 


1000 


304.794 


IB 

f 

§1 


17.462 
18.256 
19.050 
19.843 






5 
6 
7 
8 
9 
10 


1.524 
1.829 
2.134 
9 438 






11 
§1 
* 


20.637 
21.430 

22.224 






2.743 
3.048 






§1 


23.018 














n 


23.812 














u 


24.606 














i 


25.400 










1 


1 



MISCELLANEOUS TABLES. 



967 



Conversion of Inches and EigJiths into Decimals of a 
loot. 









Fractions of an Inch. 






Inches. 























* 


1 


1 


i 


1 


1 


i 





.0000 


.01041 


.02083 


.03125 


.04166 


.05208 


.0625 


.07291 


1 


.08333 


.09375 


.10416 


.11458 


.125 


.13541 


.14588 


.15639 


2 


.16666 


.17707 


.1875 


.19792 


.20832 


.21873 


.22914 


.23965 


3 


.25 


.26041 


.270 


.28125 


.29166 


.30208 


.3125 


.32291 


4 


.33333 


.34375 


.35416 


.364 


.375 


.38541 


.39588 


.40639 


5 


.41666 


.42707 


.437 


.44792 


.45832 


.46873 


.47914 


.48965 


6 


.5 


.51041 


.520 


.53125 


.54166 


.55208 


.5625 


.57291 


7 


.58333 


.59375 


.60416 


.614 


.625 


.63541 


.64588 


.65639 


8 


.66666 


.67707 


.685 


.69792 


.70832 


.71773 


.72914 


.73965 


9 


.75 


.76041 


.770 


.78125 


.79169 


.80208 


.8425 


.82291 


10 


.83333 


.84375 


.85416 


.864 


.875 


.88541 


.89588 


.90639 


11 


.91666 


.92707 


.937 


.94792 


.95832 


.96873 


.97914 


.98965 


12 


1 foot. 


foot. 


foot. 


foot. 


foot. 


foot. 


foot. 


foot. 



Jg in. = 0.005208 ft ; & in - = 0.00265 ft. ; & in. = 0.001375 ft. 
GAEGK OTTERS. 



A 


a 


Alpha. 


B 


P 


Beta. 


r 


y 


Gamma. 


A 


S 


Delta. 


E 


e 


Epsilon. 


Z 


< 


Zeta. 


H 


V 


Eta. 


© 


e 


Theta. 


I 


i 


Iota. 


K 


K 


Kappa. 


A 


A 


Lambda. 


M 


M- 


Mu. 



N 


V 


Nu. 


H 


I 


Xi. 


O 





Omicron 


II 


7T 


Pi. 


P 


P 


Bho. 


2 


<T S 


Sigma. 


T 


T 


Tau. 


Y 


V 


Upsilon. 


<!> 


4> 


Phi. 


X 


x 


Chi. 


* 


xlf 


Psi. 


a 


u> 


Omega. 



CEMRIFICAI FORCE. 



Then 



F=: centrifugal force in pounds. 
W= weight in pounds. 
v = velocity in feet per second. 
r = radius of circle in feet. 
n — revolutions per minute. 



F — 



Wrn* 
2933 



ANGULAR VELOCITY. 

The number of degrees per second through which a body revolves about a 
center. 

w = 2w n 
where 

w == angular velocity. 

n = revolutions per second. 

FRICTION. 

The following laws of friction are only approximate, the first not being 
true where pressures are very great, and the third beyond a velocity of 150 
feet per minute. 



968 



MISCELLANEOUS TABLES. 



1. Friction varies directly as the pressure on the surfaces in contact. 

2. Friction is independent of the extent of the surface in contact. 

3. Friction is independent of the velocity, when the surfaces are in motion. 

4. Rolling friction varies directly as thejjressure, and inversely as the diam- 

eter of the rolling bodies, where the cylinders or balls are of the same 
substances, and are pulled or pushed, as in a car or wagon. 

Where the load is propelled, by a crank fixed on the axle, the law it 
reversed. 

TEMPERATURE, or INTENSITY OE HEAT. 



Fahrenheit. 

212° 
32° 



Centigrade. 

100° 

0° 



Reaumur, 
80° 
0° 



Standard Points — 
Boiling point of water under { 
one atmosphere . . . . j 
Melting point of ice .... 

(A tSr U yoBly r0 . ; k ". OWn . by } =ahout-461°.2 -274° 

9° Fahrenheit = 5° Centigrade = 4° Reaumur. 

^ Temp. Cent. + 32° = j Temp. Beau. + 32° 



— 219°.2) 



Temp Fah. 
Temp. Cent. 
Temp. Beau. 



(Temp. Fah. 
(Temp. Fah. 



32°) = - Temp. Beau. 



32°) 



Temp. Cent. 



Table of Compa 


rison of Different Thermometers. 


Fah. 


Beau. 


Cent. 


Fah. 


B£au. 


Cent. 


Fah. 


Beau. 


Cent. 


212 


80.0 


100.0 


180 


65.7 


82.2 


148 


51.5 


64.4 


211 


79.5 


99.4 


179 


65.3 


81.6 


147 


51.1 


63.8 


210 


79.1 


98.8 


178 


64.8 


81.1 


146 


50.6 


63.3 


209 


78.6 


98.3 


177 


64.4 


80.5 


145 


50.2 


62.7 


208 


78.2 


97.7 


176 


64.0 


80.0 


144 


49.7 


62.2 


207 


77.7 


97.2 


175 


63.5 


79.4 


143 


49.3 


61.6 


206 


77.3 


96.6 


174 


63.1 


78.8 


142 


48.8 


61.1 


205 


76.8 


96.1 


173 


62.6 


78.3 


141 


48.4 


60.5 


204 


76.4 


95.5 


172 


62.2 


77.7 


140 


48.0 


60.0 


203 


76.0 


95.0 


171 


61.7 


77.2 


139 


47.5 


59.4 


202 


75.5 


94.4 


170 


61.3 


76.6 


138 


47.1 


58.8 


201 


75.1 


93.8 


169 


60.8 


76.1 


137 


46.6 


58.3 


200 


74.6 


93.3 


168 


60.4 


75.5 


136 


46.2 


57-7 


199 


74.2 


92.7 


167 


60.0 


75.0 


135 


45.7 


57.2 


198 


73.7 


92.2 


166 


59.5 


74.4 


134 


45.3 


56.6 


197 


73.3 


91.6 


165 


59.1 


73.8 


133 


44.8 


56.1 


196 


72.8 


91.1 


164 


58.6 


73.3 


132 


44.4 


55.5 


195 


72.4 


90.5 


163 


58.2 


72.7 


131 


44.0 


55.0 


194 


72.0 


90.0 


162 


57.7 


72.2 


130 


43.5 


54.4 


193 


71.5 


89.4 


161 


57.3 


7L6 


129 


43.1 


53.8 


192 


71.1 


88.8 


160 


56.8 


71.1 


128 


42.6 


53.3 


191 


70.6 


88.3 


159 


56.4 


70.5 


127 


42.2 


52.7 


190 


70.2 


87.7 


158 


56.0 


70.0 


126 


41.7 


52.2 


189 


69.7 


87.2 


157 


55.5 


69.4 


125 


41.3 


51.6 


188 


69.3 


86.6 


156 


55.1 


68.8 


124 


40.8 


51.1 


187 


68.8 


86.1 


155 


54.6 


68.3 


123 


40.4 


50.5 


186 


68.4 


85.5 


154 


54.2 


67.7 


122 


40.0 


50.0 


185 


68.0 


85.0 


153 


53.7 


67.2 


121 


39.5 


49.4 


184 


67.5 


84.4 


152 


53.3 


66.6 


120 


39.1 


48.8 


183 


67.1 


83.8 


151 


52.8 


66.1 


119 


38.6 


48.3 


182 


66.6 


83.3 


150 


52.4 


65.5 


118 


38.2 ' 


47.7 


181 


66.2 


82.7 


149 


52.0 


65.0 


117 


37.7 


47.2 



MISCELLANEOUS TABLES. 969 

Xahle of Compa rison of Different Thermometers — Continued. 



rah. 


Reau. 


Cent. 


Fan. 


Reau. 


Cent. 


Fan. 


Reau. 


Cent. 


116 


37.3 


46.6 


70 


16.8 


21.1 


24 


—3.5 


—4.4 


115 


36.8 


46.1 


69 


16.4 


20.5 


23 


—4.0 


—5.0 


114 


36.4 


45.5 


68 


16.0 


20.0 


22 


—4.4 


—5.5 


113 


36.0 


45.0 


67 


15.5 


19.4 


21 


—4.8 


—6.1 


112 


35.5 


44.4 


66 


15.1 


18.8 


20 


—5.3 


—6.6 


111 


35.1 


43.8 


65 


14.6 


18.3 


19 


—5.7 


—7.2 


110 


34.6 


43.3 


64 


14.2 


17.7 


18 


—6.2 


—7.7 


109 


34.2 


42.7 


63 


13.7 


17.2 


17 


—6.6 


—8.3 


108 


33.7 


42.2 


62 


13.3 


16.6 


16 


—7.1 


—8.8 


107 


33.3 


41.6 


61 


12.8 


16.1 


15 


—7.5 


—9.5 


106 


32.8 


41.1 


60 


12.4 


15.5 


14 


—8.0 


—10.0 


105 


32.4 


40.5 


59 


12.0 


15.0 


13 


—8.4 


—10.5 


104 


32.0 


40.0 


58 


11.5 


14.4 


12 


—8.8 


—11.1 


103 


31.5 


39.4 


57 


11.1 


13.8 


11 


—9.3 


—11.6 


102 


31.1 


38.8 


56 


10.6 


13.3 


10 


—9.7 


—12.2 


101 


30.6 


38.3 


55 


10.2 


12.7 


9 


—10.2 


—12.7 


100 


30.2 


37.7 


54 


9.7 


12.2 


8 


—10.6 


—13.3 


99 


29.7 


37.2 


53 


9.3 


11.6 


7 


—11.1 


—13.8 


98 


29.3 


36.6 


52 


8.8 


11.1 


6 


—11.5 


—14.4 


97 


28.8 


36.1 


51 


8.4 


10.5 


5 


—12.0 


—15.0 


96 


28.4 


35.5 


50 


8.0 


10.0 


4 


—12.4 


—15.5 


95 


28.0 


35.0 


49 


7.5 


9.4 


3 


—12.8 


—16.1 


94 


27.5 


34.4 


48 


7.1 


8.8 


2 


—13.3 


—16.6 


93 


27.1 


33.8 


47 


6.6 


8.3 


1 


—13.7 


—17.2 


92 


26.6 


33.3 


46 


6.2 


7.7 





—14.2 


—17.7 


91 


26.2 


32.7 


45 


5.7 


7.2 


—1 


—14.6 


—18.3 


90 


25.7 


32.2 


44 


5.3 


6.6 


—2 


—15.1 


—18.8 


89 


25.3 


31.6 


43 


4.8 


6.1 


—3 


—15.5 


—19.4 


88 


24.8 


31.1 


42 • 


4.4 


5.5 


—4 


—16.0 


—20.0 


87 


24.4 


30.5 


41 


4.0 


5.0 


—5 


—16.4 


—20.5 


86 


24.0 


30.0 


40 


3.5 


4.4 


—6 


—16.8 


—21.1 


85 


23.5 


29.4 


39 


3.1 


3.8 


—7 


—17.3 


—21.6 


84 


23.1 


28.8 


38 


2.6 


3.3 


—8 


—17.7 


—22.2 


83 


22.6 


28.3 


37 


2.2 


2.7 


—9 


—18.2 


—22.7 


82 


22.2 


27.7 


36 


1.7 


2.2 


—10 


—18.6 


—23.3 


81 


21.7 


27.2 


35 


1.3 


1.6 


—11 


—19.1 


—23.8 


80 


21.3 


26.6 


34 


0.8 


1.1 


—12 


—19.5 


—24.4 


79 


20.8 


26.1 


33 


0.4 


0.5 


—13 


—20.0 


—25.0 


78 


20.4 


25.5 


32 


0.0 


0.0 


—14 


—20.4 


—25.5 


77 


20.0 


25.0 


31 


—0.4 


—0.5 


—15 


—20.8 


—26.1 


76 


19.5 


24.4 


30 


—0.8 


—1.1 


—16 


—21.3 


—26.6 


75 


19.1 


23.8 


29 


—1.3 


—1.6 


—17 


—21.7 


—27.2 


74 


18.6 


23.3 


28 


—1.7 


—2.2 


—18 


—22.2 


—27.7 


73 


18.2 


22.7 


27 


—2.2 


—2.7 


—19 


—22.6 


—28.3 


72 


17.7 


22.2 


26 


— 2.6 


—3.3 


—20 


-23.1 


—28.8 


71 


17.3 


21.6 


25 


—3.1 


—3.8 









Number of Degrees Cent. = 


= Nuniher 


of Degrees fah. 




Tenths of a Degree — Centigrade Scale. 


Degrees 




Cent. 
























.0 


.1 


.2 


.3 


.4 


.5 


.6 


.7 


.8 


.9 




Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 





0.00 


0.18 


0.36 


0.54 


0.72 


0.90 


1.08 


1.26 


1.44 


1.62 


1 


1.80 


1.98 


2.16 


2.34 


2.55 


2.70 


2.88 


3.06 


3.24 


3.42 


2 


3.60 


3.78 


3.96 


4.14 


4.32 


4.50 


4.68 


4.86 


5.04 


5.22 


3 


5.40 


5.58 


5.76 


5.94 


6.12 


6.30 


6.48 


6.66 


6.84 


7.02 



970 



MISCELLANEOUS TABLES. 



\uiiibcr of Degrees Cent. == lumber of Degrees 
Fan. — (Continued.) 







Tenths of a Degree 


— Centigrade Scale 






Degrees 




Cent. 
























.0 


.1 


.2 


.3 


.4 


.5 


.6 


.7 


.8 


.9 




Fah. 


Fab. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


4 


7.20 


7.38 


7.56 


7.74 


7.92 


8.10 


8.28 


8.46 


8.64 


8.82 


5 


9.00 


9.18 


9.36 


9.54 


9.72 


9.90 


10.08 


10.26 


10.44 


10.62 


6 


10.80 


10.98 


11.16 


11.34 


11.52 


11.70 


11.88 


12.06 


12.24 


12.42 


7 


12.60 


12.78 


12.96 


13.14 


13.32 


13.50 


13.68 


13.86 


14.04 


14.22 


8 


14.40 


14.58 


14.76 


14.94 


15.12 


15.30 


15.48 


15.66 


15.84 


16.02 


9 


16.20 


16.38 


16.56 


16.74 


16.92 


17.10 


17.28 


17.46 


17.64 


17.82" 



Numoe 


r of Degrees Fah. = 


: lumber of Degrees Cent. 




Tenths of a Degree — Fahrenheit Scale. 


Degrees 




Fah. 






















.0 


.1 


.3 


.3 


.4 


.5 


.6 


.7 


.8 


.9 




Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 





0.00 


0.06 


0.11 


0.17 


0.22 


0.28 


0.33 


0.39 


0.44 


0.50 


1 


0.56" 


0.61 


0.67 


0.72 


0.78 


0.83 


0.89 


0.94 


1.00 


1.06 


2 


1.11 


1.17 


1.22 


1.28 


1.33 


1.39* 


1.44 


1.50 


1.56 


1.61 


3 


1.67 


1.72 


1.78 


1.83 


1.89 


1.94 


2.00 


2.06 


2.11 


2.17 


4 


2.22 


2.28 


2.33 


2.39 


2.44 


2.50 


2.56 


2.61 


2.67 


2.72 


5 


2.78 


2.83 


2.89 


2.94 


3.00 


3.06 


3.11 


3.17 


3.22 


3.28 


6 


3.33 


3.39 


3.44 


3.50 


3.56 


3.61 


3.67 


3.72 


3.78 


3.83 


7 


3.89 


3.94 


4.00 


4.06 


4.11 


4.17 


4.22 


4.28 


4.33 


4.39 


8 


4.44 


4.50 


4.56 


4.61 


4.67 


4.72 


4.78 


4.83 


4.89 


4.94 


9 


5.00 


5.06 


5.11 


5.17 


5.22 


5.28 


5.33 


5.39 


5.44 


5.50 



Coefficients of Expansion at Ordinary Temperatures. 

(Solids.) 





Material. 




Coefficient oJ 


Expansion. 




°F. 


°C. 




.0000114 

.0000104 

.00000306 

.0000100 

.0000055 

.0000078 

.00000961 

.00000399 

.00000521 

.00000841 

.0000046 

.000005S7 

.00000677 


.0000206 




0000187 


Brick 






.0000180 


Cement and { 




from 


.000010 


Concrete ) 




' " to 


.000014 
.0000173 
.00000719 
.00000938 
.0000151 
.0000083 
0000106 


Glass 

Gold 




from 
• - to 




Tron, cast 




.0000122 





MISCELLANEOUS TABLES. 



971 



Coefficients of Expansion- 


( Continued.) 






Material. 




Coefficient of Expansion. 




°F. 


°c. 


Lead 


.0000158 

.000004 

.0000026 

.0000049 

.00000494 

.0000020 

.0000040 

.0000067 

.0000108 

.0000056 

.00000611 

.00000689 

.0000116 

.00000276 

.0000163 


.0000284 

.000007 
.0000047 
.0000088 
00000890 


Marble (average) 
Masonry . . . 
Platinum . . . 




from 
' ' to 


Porcelain . . 


.0000036 






from 


.0000070 


Silver .... 




• ' to 


.000012 
0000194 


Slate r 


0000102 


Steel, untempered 
Steel, tempered . 
Tin 






.0000110 
.0000124 
0000209 




00000496 




.0000293 







HEAT. 

Specific Heat of Substances. 

The specific heat of a body at any temperature is the ratio of the quantity 
of beat required to raise tbe temperature of the body one degree to the 
quantity of beat required to raise an equal mass of water at or near to its 
temperature of maximum density (4°C. or 39.2°F.) tbrougb one degree. 

Specific Heats of Metals. 

(Tomlinson.) 



Metal. 


Specific Heat at 




0°C. or 32°F. 


50°C.orl22°F. 


100°Cor212°F 




0.2070 
0.0901 
0.0941 
0.1060 
0.0300 
0.0320 
0.0473 
0.0547 
0.0523 
0.0901 


0.2185 
0.0923 
0.0947 
0.1130 
0.0315 
0.0326 
0.0487 
0.0569 
0.0568 
0.0938 


0.2300 


Copper 

German Silver 

Iron 

Lead 

Platinum 

Platinum Silver ...... 

Silver 


0.0966 
0.0952 
0.1200 
0.0331 
0.0333 
0.0501 
0591 


Tin 


0.0595 


Zinc 


0.0976 



Mean Specific Heat of Platinum. 




(Pouillet.) 




2°F.) and 100°C. (212°F.) 


. . 0.0335 


" " 300°C. (572°F.) ......... 


. . 0.0343 


" 500°C. (932°F.) 


. . 0.0352 


" " 700°C. (12920-F.) 


. . 0,0360 


"■ < ; 1000°C. (1832°F.) 


. . 0.0373 


» " 1200°C. (2192°F.) 


. . 0.0382 



972 



MISCELLANEOUS TABLES. 



Mean Specific Heat of Water. 

(Regnault.) 

Between 0°C. (32°F.) and 40°C. (104°F.) . . . . . 1.0013 

" 80°C. (176°F.) ...... 1.0035 

" " " " 120°C. (248°F.) 1.0067 

'« " " " 160°C. (320°F.) 1.0109 

" " " " 200°C. (392°F.) . . . . 1.0160 

" " " " 230°C. (446°F.) 1.0204 

Mean Specific Heat of Glass (Kohlrausck) . 0.19 



Specific Heat of Grases and. Vapors at Constant Pressure. 



Substance. 



Specific Heat for 
Equal. 



Volumes. Weights 



Observer. 



Air 

Carbon monoxide 
Carbon dioxide . 
Hydrogen . . . 
Nitrogen . . . . 

Oxygen • . . . . 
Steam . . . . » 



0.2375 
0.2370 
0.29S5 
0.2359 
0.2368 
0.2405 
0.2989 



0.2375 
0.2450 
0.1952 
3.4090 
0.2438 
0.2175 
0.4S05 



Regnault 

Regnault 

Wiedermann 

Regnault 

Regnault 

Regnault 

Regnault 



Total Heat of Steam. 

British Thermal "Unit : (B. T. U.) is the quantity of beat which 
will raise tbe temperature of one pound of water one degree Fah. at or near 
its temperature of maximum density 39.1°. 

French Calorie: is the quantity of heat that will raise the tempera- 
ture of one kilogramme of pure water 1°C. at or near 4°C. 

Pound Calorie : is the quantity of heat that will raise the tempera- 
ture of one pound of water 1°C. 

1 B. T. U. = .252 Calories. 
1 Calorie = 3.968 B. T. U. 
1 lb. Calorie = 2.2046 B. T. U. 
1 pound Calorie = § Calorie. 



The JVEechanical Equivalent of Heat. 



Joule gives 
Professor Rowland, 



1 B. T. U. = 772 ft. lbs. 
1 B. T. U. = 778 ft. lbs. 

1 ft. lb. = =Js = .001285 B. T. XL 

778 

1H.P, = 42.416 B. T. U. 



(See Table of Energy Equivalents on p. 684.) 



MISCELLANEOUS TABLES. 



973 



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974 



MISCELLANEOUS TABLES. 



Specific Gravity. 



Names of Sub- 
stances. 



Woods. 

Cedar, Indian 

" American 
Citron . . . . 
Cocoa-wood . . 
Cherry-tree . . 
Cork ..... 
Cypress, Spanish 
Ebony, American 

" Indian 
Elder-tree . . 
Elm, trunk of 
Filbert-tree . 
Fir, male . . 

" female 
Hazel ". . . 
Jasmine, Spanish 
Juniper-tree 
Lemon-tree 
Lignum-vitae 
Linden-tree 
Logwood 
Mastic-tree 
Mahogany . 
Maple . . 
Medlar . . 
Mulberry . 
Oak, heart of, 60 old 
Orange-tree 
Pear-tree . 
Pomegranate-tree 
Poplar . . 

" white Spanish 
Plum-tree . 
Quince-tree 
Sassafras . . 
Spruce . . . 
old . . 
Pine, yellow . 

" white . 
Vine .... 
Walnut . . . 
Yew, Dutch . 

" Spanish 
liquids. 
Acid, Acetic . 

" Nitric . 

" Sulphuric 

" Muriatic 

" Fluoric . 

" Phosphori 
Alcohol, commer 

" pure 
Ammoniac, liquid 
Beer, lager . . 
Champagne . 
Cider .... 
Ether, sulphuric 
Naptha . . . 
Egg ... . 
Honey . . . 
Human blood 
Milk .... 



1.315 
.561 
.726 

1.040 
.715 
.240 
.644 

1.331 

1.209 
.695 
.671 
.600 
.550 
.498 
.600 
.770 
.556 
.703 

1.333 
.604 
.913 
.849 

1.063 
.750 
.944 
.897 

1.170 
.705 
.661 

1.354 
.383 
.529 
.785 
.705 
.482 
.500 
.460 
.660 
.554 

1.327 
.671 
.788 
.807 

1.062 

1.217 

1.841 

1.200 

1.500 

1.558 

833 

792 

897 

1.034 

997 

1.018 

739 

848 

1.090 

1-450 

1.054 

1.032 



'53 &,o 
I* O 



.0476 
.0203 
.0263 
.0376 
.0259 
.0087 
.0233 
.0481 
.0437 
.0252 
.0243 
.0217 
.0199 
.0180 
.0217 
.0279 
.0201 
.0254 
.0482 
.0219 
.0331 
.0307 
.0385 
.0271 
.0342 
.0324 
.0423 
.0255 
.0239 
.0490 
.0138 
.0191 
.0284 
.0255 
.0174 
.0181 
.0166 
.0239 
.0200 
.0480 
.0243 
.0285 
.0292 

.0384 
.0440 
.0666 
.0434 
.0542 
.0563 
.0301 
.0287 
,0324 
,0374 
.0360 
.0361 
.0267 

.0394 

.0524 
,0381 
,0373 



Names of Substances. 



Oil, Linseed . . 
" Olive . . . 
" Turpentine 
" Whale . . 

Proof Spirit . . 

Vinegar . . . 

Water, distilled 



Wine . 



Dead Sea 
Port ! ! 



Miscellaneous 

Ebonite ..... 
Pitch ..... 

Asphaltum 



Beeswax .... 
Butter ..... 

Camphor .... 
India rubber . . 
Fat of Beef . . . 

Hogs . . . 

Mutton . . 
Gamboge .... 
Gunpowder, loose . 
" shaken 

" solid . 



Gum Arabic . . 
Indigo .... 

Lard ..... 
Mastic .... 
Spermaceti . . 
Sugar .... 
Tallow, sheep . 
calf . . 
" ox . . 
Atmospheric air 



Oases. Vapors 



Atmospheric air . . 

Ammoniacal gas . . 

Carbonic acid , . . 

Carbonic oxid . . . 

Carbureted hydrogen 

Chlorine 

Chlorocarbonous acid 

Chloroprussic acid . 

Fluoboric acid . . . 

Hydriodic acid ... 

Hydrogen ..... 

Oxygen , 

Sulphuretted hydrogen . 

Nitrogen ....... 

Vapor of alcohol .... 
" turpentine spirits 

" water .... 

Smoke of bituminous coal 
" wood 

Steam at 212° 



.940 

.915 

.870 

.932 

.925 

1.080 

1.000 

1.030 

1.240 

.992 

.997 



1.8 
1.6 

.905 

1.650 

.965 

.942 



933 

923 

936 

923 

1.222 

900 

1.000 

1.550 

1.800 

1.452 

1.009 

947 

1.074 

.943 

1.605 

924 

934 

923 

0012 



1.000 
500 

1.527 
.972 
.972 
.500 

3.472 

2.152 
371 

4.346 
069 

1.104 
777 
972 

1.613 

5.013 
.623 
.102 
.90 



» 8 a 



.0340 
.0331 
.0314 
.0337 
.0334 
.0390 
.0361 
.0371 
.0448 
.0359 
.0361 



.0327 

.0597 

.0349 

.0341 

.0357 

.0338 

.0334 

.0338 

.0334 

.0442 

.0325 

.0361 

.0561 

.0650 

.0525 

.0365 

.0343 

.0388 

.0341 

.0580 

.0334 

.0338 

.0334 

.000043 

W'g't 

cu.ft. 

gr'ns. 

527.0 

263.7 

805.3 

512.7 

512.7 

1316 

1828 

1134 

1250 

2290 

36.33 

581.8 

9370 

512.0 

851.0 

2642 

328.0 

53.80 

474.0 

257.3 



MISCELLANEOUS TABLES. 



975 



TABLE OJP SPECIFIC GRAVITY AKD I7]tfIT 
WEIGHTS. 



Water at 



.1° Fahrenheit = 4° Centigrade ; 62.425 pounds to the cubic foot 
(authority, Kent, Haswell, and D. K. Clark). 





Specific 
Gravity. 


Authority. 


Lbs. per 
Cubic 
Foot. 


Lbs. per 
Cubic 
Inch. 


Kilos per 
Cubic 
Deem. 


Aluminum, pure cast 


2.56 


P. R. C. 


159.63 


.0924 


2.56 


" " rolled 


2.68 


" 


167.11 


.0967 


2.68 


" " anne'ld 


2.66 


" 


165.86 


.0960 


2.66 


" nickel alloy, cast 


2.85 


" 


178.10 


.1031 


2.85 


" " " rolled 


2.76 


" 


172.10 


.0996 


2.76 


" " " ann'ld 


2.74 


" 


170.85 


.0989 


2.74 


Aluminum Bronze, 10% 


7.70 


Biche. 


480.13 


.2779 


. 7.70 


" " 5% 


8.26 


" 


515.63 


.2984 


8.26 


Brass, cu. 67, zn. 33 cast 


8.32 


Haswell. 


519.36 


.3006 


8.32 


" cu. 60, zn. 40 " 


8.405 


Thurston. 


524.68 


.3036 


8.405 


Cobalt ...... 


8.50 


R.-A. 


530.61 


.3071 


8.50 


Brass, plates . . . 












high yellow . 


' 8.586 


P.R.'c'. 


535.38 


.'3098' 


' 8.586 


Bronze composition . 












cu. 90, tin 10 . 


* 8.669 


Thurston. 


541.17 


.3132' 


' 8.669 


Bronze composition. 












cu. 84, tin 16 . 


' 8.832 


Haswell. 


551.34 


.'3191 ' 


' 8.832 . 


Litbium ..... 


0.57 


B.-A. 


36.83 


.0213 


.57 


Potassium .... 


0.87 


" 


54.31 


.0314 


.87 


Sodium ..... 


0.97 


" 


60.55 


.0350 


.97 


Rubidium .... 


1.52 


" 


94.89 


.0549 


1.52 


Calcium ..... 


1.57 


" 


98.01 


.0567 


1.57 


Magnesium .... 


1.74 


" 


108.62 


.0629 


1.74 


Caesium ..... 


1.88 


" 


117.36 


.0679 


1.88 


Boron ...... 


2.00 


Haswell. 


124.85 


.0723 


2.00 


Glucinum .... 


2.07 


R.-A. 


129.22 


.0748 


2.07 


Strontium .... 


2.54 


" 


158.56 


.0918 


2.54 


Barium 


3.75 


" 


234.09 


.1355 


3.75 


Zirconium .... 


4.15 


" 


259.06 


.1499 


4.15 


Selenium ..... 


4.50 


Haswell. 


280.91 


.1626 


4.50 


Titanium ..... 


5.30 


" 


330.85 


.1915 


5.30 


Vanadium .... 


5.50 


R.-A. 


343.34 


.1987 


5.50 


Arsenic o 


5.67 


" 


353.95 


.2048 


5.67 


Columbium .... 


6.00 


Haswell. 


374.55 


.2168 


6.00 


Lanthanum .... 


6.20 


" 


387.03 


.2240 


6.20 


Niobium ..... 


6.27 


R.-A. 


391.40 


.2265 


6.27 


Didymium .... 
Cerium ..... 


6.54 
6.68 


u 


408.26 
417.00 


.2363 
.2413 


6.54 
6.68 


Antimony .... 
Chromium .... 


6.71 

6.80 


" 


418.86 
429.49 


.2424 
.2457 


6.71 

6.80 


Zinc, cast ..... 


6.861 


Haswell. 


428.30 


.2479 


6.861 


" pure .... 
" rolled .... 


7.15 


R.-A. 


446.43 


.2583 


7.15 


7.191 


Haswell. 


448.90 


.2598 


7.191 


Wolfram ..... 


7.119 


" 


444.40 


.2572 


7.119 


Tin, pure ..... 
Indium ..... 


7.29 


R.-A. 


455.08 


.2634 


7.29 


7.42 


" 


463.19 


.2681 


7.42 


Iron, cast .... 


7.218 


Kent. 


450.08 


.2605 


7.218 


" wrought . . . 
" wire .... 


7.70 


" 


480.13 


.2779 


7.70 


7.774 


Haswell. 


485.29 


.2808 


7.774 


Steel, Bessemer . . 


7.852 


" 


479.00 


.2837 


7.852 


" soft .... 


7.854 


Kent. 


489.74 


.2834 


7.854 


Iron, pure .... 


7.86 


R.-A* 


490.66 


.2840 


7.86 



976 



MISCELLANEOUS TABLES. 



TABLE OF §PFCIFIC GRAVITY. 



Continued. 



Manganese .... 

Cinnabar 

Cadmium 

Molybdenum . . . 
Gun Bronze .... 
Tobin Bronze . . . 

Nickel 

Copper, pure . . . 
Copperplates and sheet 

Bismuth 

Silver 

Tantalum .... 

Thorium 

Lead 

Palladium .... 

Thalium 

Rhodium 

Ruthenium . „ . . 

Mercury 

Uranium 

Tungsten ..... 

Gold 

Platinum 

Iridium 

Osmium 



Specific 
Gravity. 



8.00 

8.809 

8.60 

8.60 

8.750 

8.379 

8.80 

8.82 

8.93 

9.80 

10.53 

10.80 

11.10 

11.37 

11.50 

11.85 

12.10 

12.26 

13.59 

18.70 

19.10 

19.32 

21.50 

22.42 

22i48 



Authority, 



R.-A. 

Haswell. 

R.-A. 

Haswell. 

A. C. Co. 

R.-A. 

A. of C. M. 
R.-A. 



Lbs. per 


Lbs. per 


Cubic 


Cubic 


Foot. 


Inch. 


499.40 


.2890 


505.52 


.2925 


536.85 


.3107 


536.85 


.3107 


546.22 


.3161 


523.06 


.3021 


549.34 


.3179- 


550.59 


.3186 


556.83 


.3222 


611.76 


.3540 


657.33 


.3805 


674.19 


.3902 


692.93 


.4010 


709.77 


.4108 


717.88 


.4154 


739.73 


.4281 


755.34 


.4371 


765.33 


.4429 


848.35 


.4909 


1167.45 


.6755 


1192.31 


.6900 


1206.05 


.6979 


1342.13 


.7767 


1399.57 


.8099 


1403.31 


.8121 



Kilos per 
Cubic 
Deem. 



8.00 

8.098 

8.60 

8.60 

8.750 

8.379 



10.53 
10.80 
11.10 
11.37 
11.50 
11.85 
12.10 
12.26 
13.59 
18.70 
19.10 
19.32 
21.50 
22.42 
22.48 



Anthorities — R.-A. — Professor Roberts-Austen. 

Haswell — Haswell's Engineer's Pocket Book. 

P. R. C. — Pittsburg Reduction Co.'s tests. 

Kent — Kent's Mechanical Engineer's Pocket Book. 

Thurston — Report of Committee on Metallic Alloys of U.S. 

Board appointed to test iron, steel, and other metals. 

Thurston's Materials of Engineering. 
Riche — Quoted by Thurston. 
A. C. Co. — Ansonia Brass and Copper Co. 
A. of C. M. — Association of Copper Manufacturers. 

SPECIFIC GRAVITY AT ©2° FAHBF5THEIT OF 
AJLYUMiaJUifi: AX** ALrMIUfUM AJLXOYS. 

Aluminum Commercially Pure, Cast ' 2.56 

Nickel Aluminum Alloy Ingots for rolling . • • 2.72 

Casting Alloy 2.85 

Special Casting Alloy, Cast 3.00 

Aluminum Commercially Pure, as rolled, sheets and wire . , . , . 2.68 

" " " Annealed » • 2.66 

Nickel Aluminum Alloy, as rolled, sheets and wire ........ 2.76 

Sheets Annealed ........... 2.74 

Weig-lit. 

Using these specific gravities, assuming water at 62 degrees Fahrenheit, 
and at Standard Barometric Height, as 62.355 lbs. per cubic foot (authority, 
Kent and D. K. Clark). loom .„ 

Sheet of cast aluminum, 12 inches square and 1 inch thick, weighs 13 .3024 lbs. 
Sheet of rolled aluminum, 12 inches square and 1 inch thick,weighs 13.9259 lbs. 
Bar of cast aluminum , 1 inch square and 12 inches long, weighs 1.1085 lbs. 
Bar of rolled aluminum, 1 inch square and 12 inches long, weighs 1.1605 lbs. 
Bar of aluminum, cast, 1 inch round and 12 inches long, weighs .8706 lbs. 
Bar of rolled aluminum, 1 inch round and 12 inches long, weighs .9114 lbs. 



INDEX. 



Acceleration, horse-power of, 

447 
Accumulators, electric, 552 
Adhesion of cement, 796 
Aerial cable, specifications for, 171 

conductors, resistance of, 43 
A. 1. E. E. report on standardization, 

Air-pumps, 923 

Air space in grates, 831. 

Aging of iron, 344 

Alarm, burglar, wiring, 139 

Alarms, fire, for U.S.N., 753 

Alloys, relative resistance of, 181 

Alternating current, arc lamps, 394 

armature windings, 259 

circuits, measuring power in, 51 

conductors, 103 

dynamos, 230 

electro-magnets, 87 

E.M.F. and current in terms of d. 
c, 288 

motors, 273 

switchboards, 590 

wiring chart and table, 136, 137 

wiring formula, 130 

wiring, 124 
Alternators, G. E. Co., single phase, 

241 
Alternators in parallel, 269 
Alternators, single phase, 241 
Aluminum, conductors, 174-179 

data on, 174 

process, Cowles's, 680 

process, Hall's, 680 

production of, 681 

weight and specific gravity, 976 
Ammeters, 25 

Ammunition hoists, electrically op- 
erated, 740 
Amperes per car, 454 
Analysis of coals, proximate, 852 
Analysis of coke, 853 
Angular velocity, 967 
Annealing of armor plate, 693 
Annunciator wiring, 139 . 
Anthracite coal, properties of, 851 
Anti-induction cables, 150 
Arc circuits, insulation resistance 

of, 59 
Arc lamp carbons, 396 
Arc lamps, continuous current, 393 



Arc lamps, alternating current, 394 

candle-power of, 398 

efficiency of, 399 

inclosed, 394 

installation of, N.E.C., 770 

regulation of, 395 

switchboards, 592 

trimming, 402 
Ardois's system of signaling, 735 
Armature cores, energy dissipation 
* in, 80 

reaction, 264 

Avindings, 251 

windings for rotaries, 291 
Armatures, alternating current, 259 

cores, 250 

faults in, 329 

heating of, 263 
Armor plate, annealing of, 693 
Army, electricity in the, 711 
Arrangement of railway feeders, 508 
Arresters, Garton lightning, 614 

lightning and current for tele- 
phones, 653 

lightning, for light and power, 601 

non-arcing lightning, 602 
Automatic telephone switches, 650 
Axle speed, 455 
Ayrton & Perry's photometer, 390 

linker's formula for columns, 803 
Balance, Kelvin electric, 33 
Balancing coils for arc lamps, 400 
Balancing of three-phase lines, 121 
Ballistic galvanometer. 24 
B. & S. gauge, law of, 203 
Baths for plating, 678 
Batteries, dry, 17 

E.M.F. of, 53 

internal resistance of, measure- 
ment of, 62 

Leclanche cell, 15 

resistance of, 42 

secondary, or storage, 552 
Battery cell, Fuller, 15 

cells, arrangement of, 18 

common, system, 658 

Edison-La Ian de, 16 

gravity cell, 14 
Battle order indicators, 750 
Beams, flexure of, 810 

of uniform strength, 814 



977 



978 



INDEX. 



Beams, safe load on southern pine, 
822 

special forms, coefficient of 
strength, 813 

white pine, formula for, 821 
Bell wiring, 137 
Belt, length of, 953 

length of, in a roll, 953 

weight of, 953 
Belting, horse-power of, 951 
Bends in pipe, loss of head due to, 

870 
Bituminous coal, properties of, 851 
Block signals, 432 
Board of fire underwriters' rules, 

762 
Board of trade tramway regulations, 

504-508 
Boat cranes, electrically operated, 

742 
Boiler, collapsing pressure of flues, 
915 

horizontal return tubular, 829 

horizontal return tubular, height 
above grate, 831 

marine, 829 

plate, ductility of, 835 

Scotch, 829 

settings, 836 

settings, dimensions, 838 

test report, 885, 886 

tests, A.S.M.E. rules, 879 

tubes, dimensions lap-welded, 914 

vertical fire tube, 829 
Bonding, test of rail, 519-522 
Bonds, rail, 502 
Booster system, railway, 514 
Boosters, continuous current, 285 

for storage batteries, 568 
Boulenge chronograph, 715 
Brackets for railway poles, 441 
Brake controllers. 484 
Brake horse-power, 918 
Brakes, emergency, 465 
Brass, composition of rolled, 825 

weight of sheet and bar, 825 
Breakers, circuit, 596 
Brick chimneys, dimensions and 
cost, 845 

foundations, 794 

work, 823 
Bricks, sizes, 823 

weight and bulk of, 824 
Bridge, Carv-Foster, 40 

post-office, 39 

slide wire, 40 

Wheat-stone's, 28-38 
Bridging system, telephone, 664 
Brill cars, dimensions of, 466 
British thermal unit, 972 
Brown's rail bond tester, 522 
Building laws, N. Y. Citv, 803 
Bulk of bricks, 824 
Bunsen's photometer, 390 
Burglar-alarm wiring, 1.39 
Burton electric forge, 693 
Bus excited dynamos, 588 
Bushel, 961 



CaHle, aerial, specifications, 171 

joints, 201 

testing, 220 
Cables and wires, faults in, 226 

anti-induction, 142 

compound, 229 

conductivity of, 228 

crosses in, 225 

data on, 158 

lead-covered, 166 

loop test of, 226 

paper insulated, 166 

underground, 652 
Calcium carbide, production of, 678, 
Calculation of conducting systems, 

510 
Calorie, French, 972 

pound, 972 
Calorimeter, Carpenter's, quality 
curves, 894 

Carpenter's throttling, 890 

diagram for throttling, 892 

separating, 893 

throttling, 889 
Candle-power of arc lamps, 398 

of incandescent lamps, 404 

spherical, 399 
Capacity, arrangement of con- 
densers for measurement of, 46 

condensers for standard, 28 

effects on circuits, 105 

inductive of lines, 111 

measurement of, 46 

of cables, tests of, 224 

of conductors, 110 
Car, equipment list for one, 480 

heating, cost of, 690 

heating, electric, 499, 689 

horse-power per, 450 

lighting, electric, 547 

wiring diagrams, 476-480 

wiring, rules for, N.E.C., 775 
Carbide of calcium, production of. 

677 
Carbons, arc light, 396 
Carpenter's calorimeter, 890 
Carrying capacity of copper wire, 
153 ; table, 769, 788 

capacity of wires, National Elec- 
trical Code, 768, 788 
Cars, Brill, dimensions of, 466 

dimensions of, 466-469 

double truck, power required for, 
453 

headway of, 457 

heating by electricity, 499 

heating electrically, 689 

horizontal effort, 452 

single truck, power required by, 
453 

weight of, 470 
Cary-Foster Bridge, 40 
Cast-iron columns, solid, strength 
of, 807 

-iron, test, 796 
Caustic soda, production of, 677 
Cell, chloride of silver, 15 

Edison-Lalande, 16 



INDEX. 



979 



Cell, Fuller battery, 15 

gravity, 14 
Cells, battery, arrangement of, 18 
Cement, adhesion to bricks or rub- 
ble, 796 

and sand, 796 

average strength of neatr, 796 

mortar, 795 

Portland, recommendations, 796 
Centigrade in Fahr., equivalents, 969 
Central stations, storage batteries 

in, 560-576 • 

Centrifugal force, 967 

tension in fly-wheels, 925 
Characteristics of dynamos, 245 
Charging current per mile of circuit, 
114 

storage batteries, 558 
Chemical action in storage batteries, 

553 
Chemistry, electro, application of, 

676 
Chimney construction, 841 

height of, 844 

table, 840, 841 

thin shell brick, 842, 843 
Chimneys, brick, dimensions and 
cost of, 845 

dimensions and cost of iron 
(guyed), 846 

draught power, 840 

steel plate, 845 
Chloride of silver cell, 15 
Choke coils, 605 
Chronograph, Boulenge, 715 

Schmidt, 718 

Schultz, 717 

Squier-Crehore, 720 
Circuit-breakers, 596 

-breakers, high potential, 597 

-breakers, time element for, 600 

magnetic, principle of, 82 
Circuits, alternating current, meas- 
uring power in, 51, 325 

arc, insulation resistance of, 59 

balancing of three-phase, 118 

incandescent, conductors for, 101 

metallic, requirements of, 651 

metallic telephone, 651 

overhead, on poles, 651 

tests of railway, 516-520 

underground, telephone, 652 
Circulating pumps, 924 
Clay, foundation on, 792 
Coal, anthracite, properties of, 851 

bituminous, properties of, 851 
Coals, heating value of, 850 

proximate analyses, 852 

space required to stow a ton, 853 
Coast-defense guns, manipulation 

of, 721 
Code, National Electrical, 762 
Codes, telegraphic, 642 
Coefficient, of expansion, 970 

of induction, measurement of, 48 

of self-induction, definition of, 47 

temperature, of pure copper, 185 

tractive, 458 



Coils, balancing, for arc lamps, 400 

choke, 605 
Coke, analysis of, 853 

weight and bulk, 853 
Collapsing pressure, boiler flues, 915 
Column of water, comparison with 

mercury column, 929 
Columns, Baker's formula, 803 

Gordon's formula, 802 

Hodgkinson's formula, 802 

hollow cast iron, strength, 807 

hollow cylindrical, strength, 808 

N. Y. City building laws, 803 

pillars or struts, 802 

solid cast iron, strength, 807 

wrought iron, strength, 809 
Combustibles, table of, 848 
Combustion of fuels, draft power 
for, 844 

rate of, due to chimney height, 
844 
Common-battery system, 658 
Commutating machines, A. I. E. E. 

report, 295 
Comparison of columns of water in 
feet, 929 

of thermometers, 968 
Composition of gases, 855 
Compound cables, 229 

engines, cylinder ratios, 919 
Concrete foundations, 794 
Condensation, in steam pipes, 904 

in heating pipes, 904 
Condenser, ejector, 923 

jet, 921 

surface, 922 
Condensers, and pumps, 921 

arrangement of electrical, 46, 223 

standard electrical, 28 
Condensing engines, number of ex- 
pansions for, 919 
Conducting system, calculation of, 

510-514 
Conductivity of rabies, 228 
of copper, 14u 

measurement of, with millivolt- 
meter, 62 
Conductors, aerial, resistance of, 43 

aluminum, 174 

ampere capacity of copper, 769 

calculation of size, 99 

copper, 140 

for alternating current, 103 

for electrical distribution, 97 

for incandescent circuits, 101. 

heating of bare, 153 

lightning, 701 

properties of, 140 

relations and dimensions of, 92 

street railway, drop in, 446 
Conduit railway systems, 531-536 

Avork, National Electrical Code, 
772, 780 
Connections, ground for lightning 
arresters, 607 

ground, N.E.C., 767 
Constants, hysteretic, 72 
Construction, chimney, 841 



080 



Contact plate system of railway, 

543-546 
Continuous current dynamos, 230 

current motors, 270 
Controllers, installation of, 475 
dimensions of, 487 
electric brake, 484 
rheostatic, 483-485 
series parallel, 481-48G 
Converter armature windings, 291 
Converters, rotary, 286 
Cooking, electric, 685 
electric, cost of, 685 
Copper bar data, table of, 587 
conductivity of, 140 
data, 140 

electrolytic refining of, 681 
Copper-plating, 679 
Copper, sulphate, resistance of, 
G76 
temperature coefficient of pure, 

185 
weight of round bolt, 825 
wire, hard-drawn, 150 
wire table, 142 

wire table, National Electrical 
Code, 769 
Core losses, 72 

loss, test for, 312 
Cores, armature, energv dissipation 
in, 80 
armature, 250 
Cost and dimensions of iron chim- 
neys, 846 
of arc and incandescent lighting, 

414 
of electric cooking, 685 
of electric heating of cars, 690 
of operating mining plants, 696-700 
Cowles's aluminum process, 681 
Cranes, boat, electrically operated, 

742 
Cross arms, dimensions of, 219 
Crosses in cables, 225 
Cubic measures, metrical equiva- 
lent, 964 
Current, charging, per mile of cir- 
cuit, 134 
and E.M.F. alternating in terms 

of d, c, 288 
capacity of copper wire, 769 
consumption per car, 454 
densities for various metals, 269 
density in street railway conduc- 
tors, 445 
measuring with voltmeter, 56 
wave form of, 705 
Curves and grades, 423, 428 
magnetization, 65 
magnetization of dynamos, 245 
of eddy current loss, 78 
of efficiency of dynamos, 247 
railway, effort exerted on, 453 
railway, 423 
Cutouts, installation of, National 

Electrical Code, 781 
Cylinder ratios, compound engines, 
919 



Deck winches, electrically oper- 
ated, 744 
Deflection table, for wire spans, 

209-218 
Densities, average current, for vari- 
ous metals, 269 
of flux, 66 
Density of current in street railway 

conductors, 445 
Depreciation on street railways, 498 
Diagrams for car wiring, 476-480 
Dielectrics, resistance of, 193 
disruptive value of, 194-197 
strength, A.I.E.E. report, 301 
values of various (table), 197 
Diffusion and distribution of light, 

409 
Dimensions and cost of iron chim- 
neys, 846 
of boiler settings, 838 
of controllers, 487 
of cross arms, 219 
of railway cars, 466-469 
Dip in span wire, 439 
Direct current switchboards, 589 
Direct deflection method, resistance 

test, 220 
Discharge of water through an ori- 
fice, 935 
Disruptive value of dielectrics, 194 
Distribution and diffusion of light, 
409 
of light by incandescent lamps, 

412 
system, economical conditions, 93 
Ditches, data for flumes and, 933 
Double truck cars, power required 

by, 453 
Draft power of chimneys, 840 
power for combustion of fuels, 
844 
Draw-bar pull test, 522 
Drop in pressure at end of railway 
line, test of, 519 
in street railway conductors, 446 
Dry batteries, 17 
Ductility of boiler plate, 835 
Duplex telegraphy, 639 

telephony, 661 
Dynamo and motor regulation, A.I. 
E.E. report, 301 
bus excited, 588 
Dynamo rooms, N.E.C., 762 
Dynamometer, electro, 32 
Dynamos, alternating current, 230 
characteristics of, 245 
continuous current, 230 
efficiency test of, 319 
friction loss in, 312 
gyrostatic action on, 266 
Hopkinson's efficiency test of, 321 
insulation measurement of, 6U 
method of exciting, 588 
resistance of, 43 
stray field in, 237 
Thompson-Ryan, 265 
Dynamos and motors, efficiency of, 
294 



INDEX. 



981 



Dynamos and motors, hysteresis loss 
in, 313 

E.M.F. of, 53, 230 

for U. S. Navy, 727 

rating of, 303 

standards and testing, 293 

temperature rise in, 307 

test for regulation of, 310 

tests of, 306 
Dynamotors, 284 

Earth, soft, foundation on. 793 
Economical distributing conditions, 
93 

Economizers, tests of, 874, 875 

fuel, 873 
Eddy current factors, 79 

current, loss in dynamo and mo- 
tor, 313 

current loss curves, 78 

currents in iron cores, 72 
Edison-Lalande cell, 16 
Efficiency curves of dynamos, 247 

of arc lamps, 399 

of heating apparatus, 688 

of incandescent lamps, 402 

test of dynamos, A. I.E. E. report, 
319 

test of motors, 325 

test of railway motors, 523 
Ejector condenser, 923 
Elastic limit, 804 
Elasticity, modulus of, 804 
Electric accumulators, 552 

arc, heat of, 400 

brake controllers, 484 

cooking, 685 

lighting, 386 
Electric car heating, 499, 689 

forge, Burton, 693 

fuses for gun firing, 722 

power transmission, 99, 549 

welding, 691 
Electrical code, national, 762 

forging, 691 

measurements, 38 

standardization, A.I.E.E. report, 
293 

units, 2-4 ■ 

units, international, 9 
Electricity meters, 615 
Electro-chemistry, application of ,677 

dynamometer, 32 

magnetic railway system, 536 
Electrolysis, 675 

of pipes, 524-529 
Electrolytic refining of copper, 681 
Electromagnetic units, 5 
Electro-magnets, alternating-cur- 
rent, 87 

depth of winding for, 87 

heating of, 87 

lifting power of, 83 

M.M.F. of, °1 

permissible amp. for (table), 88 

properties of, SI 

relation between constants of, 86 

winding of, 84 



Electrometallurgy, 678 
Electrometer method for measure- 
ment of E.M.F.,45 
Electrometers, 30 

Electromotive force of dynamos, 230 
Electroplating, 678 

baths for, 678 

gold, 679 
Electrostatic units, 4 

voltmeter, 31 
Electrotyping, 678 
Elements of usual sections, 805, 806 
Elevated railway data, 471-474 
Elevation of outer rail, 428 
Emergency brakes, 465 
E.M.E., wave form of, 705 

of batteries, measurement of, 53 

of dynamos and motors, 53 

measurement of, 45 
Energy and work, units of, 12 

electrical, distribution, 92 
Engine telegraphs, U.S. Navy, 750 
Engines, condensing, number of ex- 
pansions for, 919 

compound, cylinder ratios of, 919 
Equation of steam pipes, 907 

of steam pipes, table, 909 
Equipment list for one car, 480 
Evaporation, factors of, 895 
Exciting dynamos, method of, 588 
Exhaust injectors, 868 

steam, pump, 872 
Expansion, coefficients of, 970 

of metals, 184 

of water, 858 
Expansions, number of, for con- 
densing engines, 919 

Factor of safety, 804 
Factors of eddy current, 79 

hysteresis, 73 

inductance, 107 

of evaporation, 895 

of evaporation, table, 896 
Fahrenheit in centigrade equiva- 
lent, 970 
Fans, ventilating, for U. S. Navy, 

744 
Faults in armatures, 329 

in incandescent lamps, 408 

in wires or cables, 226 

of car motors and remedies, 523 
Feeder points, location of, 512 
Feeders, arrangement of railway, 

508-510 
Feed-water heaters, 871 

pipes, sizes of, 869 

purification by boiling, 861 

saving by heating, 871 
Field magnets, 265 

telegraph and telephone, 726 
Fire alarms, for U. S. Navy, 753 
Fire, temperature of, 849 

underwriters' rules, 762 
Flanges, standard pipe, 915 
Flat-irons, electric, 691 
Flat plates, safe pressure on, 834 

rolled iron, weight of, 797 






982 



INDEX. 



Flexure of beams, fundamental 

formula', 810 
Flow of steam through pipes, 905 

of water in pipes, 869 

of water over weirs, 937 
Flue areas and gas passages, 831 
Flues, boiler, collapsing pressure, 

915 
Flumes and ditches, data for, 933 
Flux densities, 06 

magnetic, formula for, 82 
Fly-wheels and pulleys, centrifugal 

tension in, 925 
Foot valve, 924 
Force, centrifugal, 967 
Forge, Burton Electric, 693 
Forging electrically, 691 
Foundations, 792 

brick, 794 

concrete, 794 

of I-beam, 795 

permissible load upon, 794 

on clay, 792 

on piles, 793 

on rock, 792 

on sand or gravel, 792 

on soft earth, 793 

stone, 794 
Friction, 967 

loss in dynamos and motors, 312 

of water in pipes, 870 
Fuel, 846 

economizers, 873 

kinds and ingredients of, 846 
Fuels, gaseous, 855 

heat of combustion, 847 

liquid, 854 
Fuller cell, 15 
Furnaces for oil fuels, 855 
Fuse data, 694 

table, 204 
Fuses, electric, for gun-firing, 722 

for railway circuits, 465 

installation of, N.E.C., 782 
Fusion of metals, temperature de- 
termined by, 849 



Gallon, 961 

Galvanized iron wire data, 154 
Galvanometer, ballistic, 24 

Northrup's, 25 

tangent, 21 

Thompson, 22 
Galvanometers, 20 

resistance of, 42 
Garton lightning arrester, 614 
Gas lighting, electric, N.E.C., 786 

light wiring, 139 

passages and flue-area, 831 
Gaseous fuels, 855 
Gases, composition of, 855 

and vapors, specific heat of, 972 
Gauge, B. & S., law of, 203 
General electric single-phase alter- 
nators, 241 

electric surface contact railway, 
543-547 



Generator magneto, 650 

sets, tests of U. S. Navy, 727 
German silver wire, data on, 180 
Gold-plating, 680 

Gordon's formula, for columns, 802 
Grades and curves, 423, 428 

horizontal effort on, 454 
Grate surface, 831 

surface per horse-power, 831 
Grates, air-space in, 831 
Gravel, foundation on, 792 
Gravitv cell, 14 
Greek letters, 967 

Ground connections for lightning 
arresters, 607 

connections, National Electrical 
Code, 767 

return drop, test of, 518 
Guard wires, 445 
Guns, manipulation of, 721 
Gutta-percha covered wires, joint- 
ing, 199 

data on, 198 
Guys for trolley wire, 444 
Gyration, radius of, 805 
Gyrostatic action on dynamos, 266 

Ha!!'* aluminum process, 681 
Hard drawn copper, weight of wire, 

142 
Haulage in mines, cost of, 696 
Headway of cars, 457 
Heat-conducting power of metals, 
185 

intensity of, 968 

mechanical equivalent of , 972 

of combustion of fuels, 847 

specific, of gases and vapors, 972 

of the electric arc, 400 

transmitted through cast-iron 
plates, 911 

units, 3, 683, 973 
Heaters, feed-water, 871 

electric, installation of, N. E. C, 
771 
Heating apparatus, efficiency of, 
688 

apparatus, portable, 779 

apparatus, principles of, 683 

cars by electricity, 499 

cars electrically, 689-690 

of armatures, 263 

of bare conductors, 153 

of electro-magnets, 87 

pipes, condensation in, 904 

surface of steam boilers, 830 

surface per horse-power, 831 

value of coals, 850 
Helm angle indicators, 750 
Hemp rope, tarred weight of, 958 
High potential circuit breakers, 597 

potential oil switches, 595 

potential systems, N.E.C., 775 

voltage transmission, 550 
Hodgkinson's formula, for columns, 

802 
Hoists, electric, for ammunition, 740 
Hollow shafts, 949 



INDEX. 



983 



Hopkinson's efficiency test of dyna- 
mos, 321 

permeability test, 67 
Horizontal effort of traction, 452 

effort on grades, 454 

return tubular boiler, 829 

tubular boiler heigbt above grate, 
831 
Horse-power, brake, 918 

boiler, to supply heating pipes, 
904 

indicated, 918 

mill power, 928 

nominal, 918 

of a running stream, 928 

of a waterfall, 927 

of acceleration, 447 

of belting, 951 

of steam boilers, 829 

of traction, 449 

of water, cubic feet table, 938 

of water, miner's inch table, 937 

per car, 450 

water flowing in a pipe, 928 
House circuits, resistance of, 43 
Human body, resistance of, 61 
Hydro-electrothermic system, 693 
Hydrometers, 555 
Hysteresis loss in transformers, 332 

factors, 73 

loss in dynamos and motors, 313 

meter, 75 
Hysteretic constants, 72 

11-beam foundations, 795 
I-beams, spacing and size, 817 
Illuminating power, 393 
Impedance and inductance table, 
117 

coil, use of, 671 

diagrams, 116 

effect of, 104 

table, 136 
Impulse water wheels, 944 
Incandescent lamps, 402 

candle-power of, 404 

distribution of light by, 412 

efficiency of, 402 

faults in', 408 

life of, 411 

proper use of, 403 

smashing point, 403 
Inches and eighths in decimal of a 

foot, 967 
Inclined planes, strains in rope on, 

958 
Inclosed arc lamps, 394 
Incrustation, causes and prevention 
of, 858 

tabular view, 859 
India-rubber, vulcanized, 198 
Indicators, battle order, 750 

helm angle, 750 

range, 753 

revolution, 750 
Inductance and impedance table, 
117 

factors, 107 



Inductance and impedance of aerial 

lines, 50 
Induction coils, connections of, 757 

factors, table, 106 

motors, 274 

motors, current taken by, 128 

motors, tests of, 324 

motors, transformers for, 127 
Induction, coefficient of self, 47 

self, effect of, 104 
Inductive capacity, 111 

resistance of lines, 106 
Inertia, moment of, 804 
Injector vs. pump for feeding boil- 
ers, 868 
Injectors, exhaust, 868 

live steam, 866 

live steam, deliveries for, 867 

performance of, 868 
Installation of arc lamps, N.E.C., 770 

of controllers, 475 

of cutouts, N.E.C., 781 

of fuses, N.E.C., 782 

of street car motors, 474 

of telephones, 653 
Insulating joints, N.E.C., 784 
Insulation of dynamos, measure- 
ment of, 60 

of light and power circuits, meas- 
urement of, 58 

of motors, measurement of, 61 

regulations, National Electrical 
Code, 777 

resistance, A.I.E.E. report, 300 

resistance, N.E.C., 764 

resistance of arc circuits, 59 

resistance of cables, 220 

resistance of circuits, 44 

test, direct deflection method, 220 
Insulators, specific resistance of, 193 
Intensities of sources of light, 386 
Intensity of heat, 968 
Intercommunicating telephone sys- 
tems, 668 
Interior lighting, 393 

telephone systems. 663 
Internal resistance of batteries, 

measurement of, 62 
International electrical units, 9 
Iron, aging of, 344 

and steel, 796 

bars, round and square, weight of, 
799 

cast, test, 796 

cores, eddy currents in, 72 

flat rolled, weight of, 797 

magnetic properties of, 64 

plate, weight of, 800 

plating, 680 

weight of, 796 

wire data, 154-157 
Irons, electric, 691 
Isolated plants, storage batteries 
for, 566 

Jet condenser, 921 
Jointing gutta-percha covered wire, 
199 



984 



INDEX. 



Joints, cable, 201 

insulating, N.E.C., 784 

of cables, testing of, 222 

per mile of track, 429 
Joly's photometer, 390 
Joule, 3 

Kapp efficiency test of dynamos, 

315 
Kelvin electric balance, 33 
electric balance tables, 36 
Krupp's resistance wires, 191 

Lamp specification for United 

States Navy, 732 
Lamps, arc, 393 

incandescent, 402 

incandescent, efficiency of, 432 
Leaded wires and cables, 1GG 
Leclanche cell, 15 
Length of belt, 953 
Leonard's system of motor control, 

272 
Letters, Greek, 967 
Life of incandescent lamps, 411 
Lifting power of electro-magnets, 83 
Light, distribution and diffusion of, 
409 

distribution of, by incandescent 
lamps, 412 

measurement of, 389 

proper use of, 411-403 

units of, 387 

velocity and intensity of, 386 
Lighting, cost of arc and incandes- 
cent, 414 

electric, 386 

electric gas, N.E.C., 786 

interior, 393 

of cars, 547 

schedules, 414-422 

-system specifications for U. S. 
Navy, 731 
Lightning and current arresters for 
telephones, 653 

arresters for light and power, 601 

arresters, function of, 601 

arresters, Garton, 614 

arresters, ground connections for, 
607 

arresters, location of, 764 

arresters, non-arcing, 602 

arresters, S.K.C., 614 

conductors, 701 

rods, installation of, 702, 704 
Lime mortar, 795 
Limit, elastic, 804 

Lineal measure, metrical equiva- 
lent, 962 
Lines, aerial, resistance of, 43 

balancing of three phase, 118 
Liquid fuels, 854 

List of equipment for one car, 480 
Load factor of railway system, 510 
Loading and training gear tor guns, 

739 
Loads, permissible on foundation 
beds, 794 



Location of feeder-points, 512 
Long-distance lines, 660 

transmission, 550 
Loop test of cables, 226 
Lord Kayleigh's method for meas- 
urement, E.M.F., 45 
Loss of charge method, 221 

eddy current, in dynamos and 
motors, 313 

of head due to bends, 870 
Losses, core, 72 
Lummer-Brodhun photometer, 392 

Machine shops, horse power in, 

758 

shops, men employed in, 758 

tools, power used by, 758 
Magnet telephone, theory of, 645 
Magnets, electro, heating of, 87 

field, 265 
Magnetic circuit, principle of, 82 

circuit of dynamos, 236 

flux, formula for, 82 

properties of iron, 64 

units, 4 
Magnetization curves, 65 

curves of dynamos, 245 
Magneto generator, 650 
M.M.F. of electro-magnets, 81 
Manganine wire, 188 
Manila ropes, centrifugal-tension, 
955 

horse-power diagram, 956 

horse-power of, 955 

weight and strength, 958 
Marine boiler, 829 
Masonry, 823 

average ultimate crushing load, 
824 
Material for one mile of overhead 

line, 436 . 
Materials, strength of, 803 
Mean effective pressure, table of, 
920 

spherical candle-power, 399 
Measurement of E.M.F. of batteries, 
55 

of capacity, 40 

of current with voltmeter, 56 

of E.M.F.,45 

of flow of water, 936 

of high resistances, 58 

of insulation of dynamos and mo- 
tors, 60 

of internal resistance of batteries, 
62 

of light, 389 

of low resistances, 57 

of mutual inductance, -19 

of power in alternating current 
circuits, 51, 325 

of resistance of human body, 61 

of self-inductance, 48 
Measurements, electrical, 38 
Measures, cubic, metrical equiva- 
lent, 964 
Mechanical equivalent of heat, 972 

stoking, 856 



INDEX. 



985 



Metallic circuits, requirements of, 

651 
Metals, expansion of, 184 

heat conducting power of, 1S5 

resistance of, 141 

separation of, 681 

specific heat of, 184 

weights and specific gravity, 975 
Meter, hysteresis, 75 
Meters, electricity, 615 

alternating current, 620 

Wright discount, 635 
Metric measures in English meas- 
ures, 965 
Metrical equivalents, of cubic meas- 
ure, 964 
Metropolitan Street Railway system, 

532-536 
Miles per hour, feet per minute 

(table), 457 
Milliken repeater, 637 
Mill power, 928 

Miner's inch measurements, 937 
Mines, electrical land, 723 

haulage in, cost of, 696 
Mining plants, operation of, 696 
Miscellaneous materials, 825 

tables, 961 
Modulus of elasticity, 804 

of elasticity and elastic resistance, 
814 
Moisture in steam, determination 
of, 889 

in steam, tables, 891 
Moment of inertia, 804 

of inertia of compound shapes, 805 
Monocyclic circuit connections, 129 

system wiring formula, 131 
Moonlight schedules, 414-422 
Mortars, cement and lime, 795 
Motor control, Leonard system, 272 

equipments, 425 

-generators, 284 

standards and testing, 293 

trucks, weight of, 464 
Motors, alternating current, 273 

car, faults and remedies, 523 

continuous current, 270 

efficiency of, 294 

efficiency, test of, 325 

E.M.F. of, 53 

friction, loss in, 312 

induction, 274 

installation of, N.E.C., 764 

insulation resistance of, 61 

measurement of insulation resist- 
ance of, 60 

railway, 424 

rating of, 303 

rating of railway, 457 

series-wound, 271 

shunt-wound, 272 

speed and torque of, 271 

synchronous, 281 

synchronous, test of, 326 

temperature, rise in, 307 

testing of railway, 522 

tests of, 306 



Motors, tests of induction, 324 

tests of, report, 322 

types of railway, 460 

weight of railway, 470 
Multiphase induction motors, 274 
Multiple-unit system, Sprague, 4S9- 

498 
Multiplex telephony, 661 
Mutual inductance, meas. of, 49 

inductance of aerial lines, 50 

induction of circuits, 120. 

H~atioiial Electrical Code, 762 
Navy, electricity in United States, 

727 
standard wires, 159 
Ness automatic telephone switch, 

672 
New York City building laws, 803 
Niagara-Buffalo transmission line, 

120 
Niagara line construction, 120 
Nickeline wire, 187-191 
Nickel plating, 680 
Non-arcing lightning arresters, 602 
Northrup's galvanometer, 25 

Ohm standard, 27 

values of, 141 
Ohm's law, 38 
Oil switch, 594 

fuel, furnaces for, 855 
Output of dynamos and motors, 266 
Overhead circuits, on poles, 651 
Overhead line construction data, 
120, 436 

railway system, 508-510 
Overload capacity of dynamos and 
motors, A.l.E.E. report, 303 

Paper insulated wires and cables, 

166 
Parallel, alternators in, 269 
Party lines, 659 
Paving, cost of, 430 
Peckhain trucks, 471 
Pelton impulse waterwheel, 943 
Permeability curves, 248 

values, 66 

test, Hopkinson's, 67 
Permeameter, 68 
Permissible loads on foundation 

beds, 794 
Petroleum, chemical composition of, 
854 

oils, chemical composition, 855 
Photometer, Ayrton & Perry, 390 

Bunsen's, 389-390 

Joly's, 390 

Lummer-Brodhun, 392 

Ritchie's, 390 

Rum ford's, 390 

Sabine's, 390 

Weber's, 391 
Piles, arrangement of, 794 

foundation on, 793 

safe load on, 793 
Pillars, columns or struts, 802, 



986 



INDEX. 



Pipe, standard flanges for, 915 

riveted hydraulic, 934 

standard dimensions, steam, gas 
and water, 912 

wooden-stave, 933 

wrought iron extra-strong, 913 
Pipes, condensation in heating, 904 

electrolysis of, 524 

equation of steam, 907 

friction of water in, 870 

sizes for feed-water, 869 
Plate iron, weight of, 800 
Plates, heat transmitted through, 

911 
Plating, copper-, 678 

electro, baths for, 678 
Platinum, specific heat of, 971 
Plotting of electrical waves, 708 
Poles for trolley systems, 438 

tubular iron and steel, 438 
Polyphase induction motors, 275 
Portland cement — recommenda- 
tions, 796 
Position indicators, 749 
Post-office bridge, 39 
Pound-calorie, 972 
Power curves, 448 

factor chart, 137 ' 

factor, determination of, 125 , 

factor, formula for, A.l.E.E. re- 
port, 305 

factor table, 106 

measurement of, in alternating 
current circuits, 51 

required for double truck cars, 453 

station, 424 

station, capacity of, 459 

station construction-chart, 791 

stations, batteries in, 575 

systems for U. S. Navy, 735 

transmission, electric, 548 
Pressure loss in water pipes, 870 

of water, table, 931 
Primary cells, 14 
Projectors, 395 

for U. S. Navy, 733 
Prony brake, 758 

brake test of motors, 322 
Properties of electro-magnets, 81 

of saturated steam, tables, 899 

of timber, 818 
Protected rail bonds, 501 
Protection of steam heated sur- 
faces, 910 
Pulleys, 951 

to find size of, 951 
Pumping hot water, 863 
Pumps, air, 923 

circulating, 924 

condensers and, 921 

duplex-cylinder, direct-act i ng, 
866 

efficiency of small direct-acting, 
864 

exhaust, 872 

feed, 8G3 

single-cylinder, direct-acting, F65 
Pure copper wire table, 151 



Purification of feed water by boil- 
ing, 861 

Q.uad ruplex telegraphy, 640 
Quality of steam by color of issuing 
jet, 895 

Radiators, electric, 689 
Radius of gyration, 805 
Kail bonding, test of, 519-522 

bonds, 502 

bonds, protected, 501 

bond tester, Brown's, 522 

bond tester, Walmsley's, 521 

elevation of outer, 428 

Avelding, 694 
Rails, conductivity of, 504 

sectional areas of, 504 

weights of, 426 
Railway circuits, boosters for, 514 

circuits, fuses for, 465 

circuits, tests of, 516, 520 

curves, 423 

curves, effort exerted on, 453 

electromagnetic, 536 

elevated, data, 471 

motor testing, 324, 522 

motors, 425 

motors, rating of, 457 

motors, types of, 460 

three-wire system, 514 
Railways, battery plants for, 575 

conduit, 531-537 

depreciation on, 498 

surface contact, 536-546 

switchboard connections, 591 

third rail, 529-531 

turnouts, 431 
Range indicators, 753 
Rate of combustion due to chimney 

height, 844 
Rates for incandescent lighting, 414 
Rating dynamos and motors, A. 1. 
E. E. report, 303 

street railway motors, 457 
Reactance coils, 361 

diagrams, 116 
Reaction of armatures, 264 
Receiver, Bell telephone, 646 

capacity, 921 

telephone, 645 
Rectifying machines, A. I. E. E. 

report, 297 
Regulation of arc lamps, 395 

of dynamos and motors, test for, 
A.l.E.E. report, 310 
Regulations of board of trade, 504- 

508 
Regulators, a. c. feeder, 362 
Renewal of lamps, 407 
Repeaters, 637 
Repeating coil, 660 
Report of A. I.E. E. committee on 
standardization, 293 

of boiler test, 885 

on water-power property, 926 
Resistance, boxes, 27 

boxes, location of, N.E.C., 763 



INDEX. 



987 



Resistance, increase in, 307 

insulation, A.l.E.E. report, 300 

insulation, N. E.G. ,764 

insulation of arc circuits, 59 

insulation of cables, 220 

insulation of circuits, 44 

internal of batteries, 62 

measurement of, 38 

measuring with voltmeter, 57 

metals, 186 

of alloys, 181 

of batteries, internal, 62 

of batteries, 42 

of dielectrics, 193 

of dynamos, measurement of, 43 

of galvanometers, 42 

of house circuits, 43 

of human body, measurement of, 
61 

of lines, inductive, 106 

of metals, 141 

of wires, 42 

ribbon, 187 

test of armature, 328 

wires, Krupp, 191 
Return circuit, 499 

drop, test of, 518 

feeder booster, 515 
Return circuits of railways, boosters 

for, 514 
Return, ground, test of drop, 578 
Reverse current circuit breakers, 

. 598 
Revolution indicators, 750 
Revolutions of car wheels, 451 
Rheostatic controllers, 483-485 
Ritchie's photometer, 390 
Riveted hydraulic pipe, 934 
Riveted steel pipes, 932 
Rock, foundation on, 792 
Rooms, dynamo, N.E.C., 762 
Rope driving, 954 
Rope, H. P. of transmission, 957 
R jpes and belts, slip of, 957 
Ropes, manila, 955 

strains in, on inclined planes, 958 
Rotary armature windings, 291 
Rotary converters, 286 
Rules for conducting boiler tests, 

879 
Rumford's photometer, 390 

Sabine's photometer, 390 

Safe carrying capacity of wires, 153 

table of, 769 
Safe load on piles, 793 

load on wooden beams, 820 
Safety, factor of, 804 
Safety valves, calculations for lever, 
877 

valves, rules, 877 
Sag of wires and cables, 205 
Sand, foundation on, 792 
Sand and cement, 796 

recommendations, 79G 
Saturation test, A. 1. E. E. report, 

327 
Saving by heating feed-water, 871 



Scale-making materials, solubility 

ot, 859 
Schedules of lighting, 414-422 

moonlight for lighting, 414 
Schmidt chronograph, 718 
Schultz chronograph, 717 
Scotch boiler, 829 
Searchlight data (table), 714 

projectors, 395 
Searchlights, 711 

for U. S. Navy, 732 
Secondary batteries, 552 
Sectional rail construction, 542 
Self-induction, effect of, 104 

coefficient of self, 47 
Semaphores, 433 
Separating calorimeter, 893 
Separation of metals, 681 
Separators, steam, 875 

tests of, 876 
Series-parallel controller, 481-486 
Series-wound motors, 271 
Settings, for boilers, 836 
Sewing-machines, power required to 

operate, 757 
Shafting, centers of bearings, 947 

cold-rolled, horse-power of, 948 

deflection of, 946 

hollow, 949 

horse-power of, 947, 949 

power and size, 945 

table for laying out, 949, 950 
Shunt boxes, 26 
Shunt-wound motors, 272 
Side brackets, for railway poles, 441 
Signaling, Ardois system, 735 
Signaling systems, National Elec- 
trical Code, 785 
Signal lights for U. S. Navy, 735 
Signals, block, 432 
Silicon bronze wire, 219 
Silver, chloride of, cell, 15 

electrolytic refining of, 682 
Simultaneous telegraphy and tele- 
phony, 662 
Single-phase alternators, 241 
Single-truck cars, power required 

by, 453 
Size of bricks, 823 
Size of conductors, calculation of, 

99 
Skin effect factors, 103 
Slide-wire bridge, 40 
Slip of ropes and belts, 957 
Smashing point of incandescent 

lamps, 403 
Sockets, specifications for, N. E. C, 

774, 782 
Soda, caustic, production of, 676 
Soldering fluid formula, 787 
Solid rail bonds, 500 
Sources of light, intensities of, 386 
Space required for a ton of coal, 853 
Spacing and size of I-beams, 817 
Span wire data, 440 

wire dip, 439 
Spans of wire and cable, table of, 
205 



988 



INDEX. 



Specific energy dissipation, 80 

gravity and unit weights, 975 

gravity, various substances, 974, 
975 

heat of gases and vapors, 972 

heat of metals, 184, 971 

heat of substances, defined, 971 

heat of water, mean, 972 

resistance table, 192 
Specifications for lighting system 

U. S. Navy, 731 
Specification, U. S. Navy, for incan- 
descent lamp, 732 
Speed and torque of motors, 271 

of car axle, 455 

of water through pump-passages 
and valves, 864 

recorder, 754 
Spikes, 429 
Sprague multiple unit system, 489- 

498 
Squier-Crehore Photo-Chronograph, 

720 
Standard cells, 11, 18 

pipe flanges, 915 
Standardization, report of A. I. E. 

E., 293 
Standards and testing of dynamos 

and motors, 293 
Static transformer, 331 
Station equipment, 424 
Stays, boiler head, 835 
Steam, 829 

and exhaust pipes, sizes of, 908 

and gas pipes, standard sizes, 908 

boiler braces, 836 

boiler efficiency, 831 

boilers, heating surface of, 830 

boilers, horse-power of, 829 

boilers, types, 829 

boilers, working-pressure, 832, 833 

determination of the moisture in, 
889 

engines, classification, 916 

engines, horse-power of , 918 

engines, tests of various types. 
917 

flow of, through pipes, 906 

horse-power of, 928 

moisture in, tables, 891 

outflow of, to atmosphere, 905 

pipes, 906 

pipes, condensation in, 904 

pipes, equation of, 907 

pipes, loss of heat from, 910 

ports and passages, 921 

properties of, 899 

total heat of, 972 
Stearns duplex telegraph, 641 
Steel and iron, 796 

beams, formulae for greatest sate 
load, 812 

plate chimneys, 845 

plate chimneys, brick lining, 845 

plate chimneys, foundation dimen- 
sions, 845 
Steel, weight of, 796 
Steel wire data, 154-157 



Steering gear, electrically operated, 

745 
Stone foundations, 794 
Storage batteries, 552 

advantages of, 560 

capacity of, 554 

charging, 558 

chemical action in, 553 

E.M.F. of, 554 

for isolated plants, 566 

for surface contact railway, 546 

for yachts, 571 

in power stations, 575 

installation of, 556-561 

installation of, N.E.C., 765 

manufacturers of, 563 

solutions for, 555 

source of charging current for 
testing, 582. 

testing of, 579 
Strain and deflection table for wire 

spans, 215-218 
Stranded wire cables, 157 
Stray field in dynamos, 237 
Street car motors, installation of, 
474 

car wiring cables, 160 

lighting by arc lamps, 401 

railway batteries, 575 

railway conductors, drop in, 446 

railway depreciation, 498 
Strength of bars, transverse, 810 

of beams, 814 

of beams, coefficient of strength 
of special forms, 813 

of beams, transverse, 811 

of hollow cylindrical columns, 808 

of materials, 803 

of neat cement, 796 

of riveted shell, 832 

of solid cast iron columns, 807 

of Trenton beams and channels, 
815 

of wrought iron columns, 809 
Struts, sate load for white pine, 821 
Submarine cables, testing of, 228 

data on, 173 
Substation system, 516 
Suggestions, general, National Elec- 
trical Code, 790 
Sulphate of copper, resistance of, 
677 

of zinc, resistance of, 677 
Sulphuric acid, resistance of dilute, 

675 
" Superior" wire, 188 
Supplies for installing lamps, 760 
Surface condenser, 922 

contact railway system, 536-546 

grate, 831 

grate, per horse-power, S31 

heating, of steam boilers, 830 
Suspension of trolley wire, 443 
Switchboard, diagram of connec- 
tions, Manhattan Elevated Rail- 
way, 591 
Switchooards for alternating cur- 
rent, 590 



INDEX. 



989 



Switchboards for construction of, 
585 

for arc circuits, 592 

for direct current, 589 

layout of, 585 

location of, 763 

specifications for the U. S. Navy, 
729 

telephone, 655 
Switches, automatic telephone, 650 

oil break, 594 

oil, high potential, 595 

specifications for, N.E.C., 781 
Symbols, electrical engineering, 1 

synopsis of (table), 6 
Synchronizers, 267 
Synchronous machines, A. I. E. E. 
report, 295 

motors, 281 

motors, tests of, 326 
Systems, high potential, N. E. C, 
775 

Tal»l« of combustibles, 848 

of copper wire, 143, 769 

of data on bar copper, 587 

of deflection for wire spans, 20C- 
218 

of equation of steam pipes, 909 

of factors of evaporation, 896 

of fuse data, 204 
Tables for Kelvin balance, 36 

of weights and measures, 961, 962 
Tangent galvanometer, 21 
Telegraph and telephone, field, 726 
Telegraph, anti-induction cables, 150 
Telegraphs, engine, U.S.N., 750 

cables, specifications for, 170 

codes, 642 

for U. S. Army use, 724 

wire data, 154 
Telegraphy, American, 636 

and telephony, simultaneous, 662 

duplex, 639 

European, 636 

quadruplex, 640 
Telephone, anti-induction cables, 
150 

automatic switch for, 650 
^bridging system, 664 

cables, specifications for, 169 

circuits, 651 

multiplex, 661 

switchboards, 655 

switch, Ness automatic, 672 

systems, intercommunicating, 668 

systems, interior, 663 

transmitters, Blake, 647 

transmitter, Edison carbon, 645 

transmitter, solid back, 648 

wire data, 154 

wires, aluminum, 176 
Telephones, installation and main- 
tenance of, 653 

for U. S. Army use, 724 

for U. S. Navy, 753 
Telephony, 645 

duplex and multiplex, 661 



Temperature coefficient of copper, 
185 
coefficients of conductors, 182 
effect in wire spans, 207 
of tire, 849 
of metals determined by fusion, 

'849 
or intensity of heat, 968 
rise in dynamos and motors, 307 
rise of, A.l.E.E. report, 298 
Tensile strength of copper wire 

(table), 208 
Test for core loss, 312 
for drop in pressure at end of 

trolley line, 519 
lor efficiency of dynamos, 319 
for regulation of dynamos and 

motors, 310 
of draw bar pull, 522 
of dynamos for efficiency, A.l.E.E. 

report, 319 
of dvnamos, Hopkinson's, for 

efficiency, 321 
of ground return drop, 578 
of permeability, Hopkinson's, 67 
Testing of cables, 220 
of dynamos and motors, 293, 306 
rail bonds, 519-522 
railway motors, 522 
Tests of American woods, 819 
of cables, for capacity, 223 
of economizers, 874 
of generator sets, U. S. N., 728 
of railway circuits, 516 
of street railway circuits, 516-520 
Thermal unit, British, 972 
Thermo-electric scale, 757 
Thermometers, comparison of F. R. 

and C, 968 
Third-rail systems, 529-531 
Thompson double bridge, 41 
galvanometer, 22 

method for measuring capacity, 
46 
Thompson-Ryan dynamo, 265 
Three-phase circuits, balancing of, 
121 
circuits, energy in, 233 
measurement of energy in, 325 
wiring formula, 133 
Three- wire system, railway, 514 
Throttling calorimeter, 889 
calorimeter, calculation curves 
for, 892 
Thunderstorms, safety during, 703 
Tics, railway", 429 
Time element for circuit breakers, 

600 
Tools for installing dynamos, 759 
Torque and horse-power, 465 

of motors, 271 
Track bonding, test of, 519-522 
laying, 430 
return circuit, 499 
Traction, horse- power of, 449 
Tractive coefficient, 458 
effort, 458 
force, 450 



990 



INDEX. 



Tramway regulations, Board of 

Trade, 504 
Transformer, air-blast, 338 

cores, 331 

design of, 335 

duties of, 332 

efficiencies of, 340 

equations, 334 

expense of operating, 346 

heating tests (tables), 339 

losses in (table), 333 

regulation of, 344 

static, 331 
Transformers, commercial (tables), 
347 

connections of, 366 

constant current, 357 

high potential, 356 

in connection with rotaries, 292 

testing of, 372 
Transmission, high voltage, 550 

of electric power, 99 

of power, 548 
Transmitter, Edison carbon, 645 

Blake, 647 

solid-back, 648 
Transverse strength of bars, 810 

strength of beams, formula} for, 
811 
Trenton beams and channels, 

strength, 815 
Trimming arc lamps, 402 
Trolley poles, 437 

systems, 508-520 

wire, guys for, 444 

wire, size of, 512 

wire suspension, 443 

wires, specification, N.E.C., 766 
Trucks, Peckham, 471 

weight of, 464, 470 
Tubes, sizes lap-welded boiler, 914 
Tubular iron and steel poles, 438 
Turbines, data, McCormick type, 
942 

dimensions, etc., 941-943 

dimensions of Victor, 941 

impulse, 941 

installing, 941 

parallel, outward and inward flow, 
940 
Turnouts on railways, 431 
Turret-turning system, 737 
Two-phase four-wire circuits, 123 

Underground cables, 652 

circuits, telephone, 652 

electrical construction, 203 
Underwriters' rules, 762 
Unit, British thermal, 972 

electrical and mechanical, table 
of, 684 

electrical engineering, 2 

electromagnetic, 5 

electrostatic, 4 

heat, 3 

magnetic, 4 

of energy and work, 12 

of light, 387 



U. S. Army, electricity in, 711 
standard gauge for sheet and plate 
iron and steel, 801 

Values of various dielectrics, 197 
Valves, foot, 924 

safety, 877 
Velocity, angular, 967 

of light, 386 
Ventilating fans for U. S. Navy, 744 
Vertical fire-tube boiler, 829 
Voltage regulation for incandescent 

lamps, 405 
Volt, determination of, 10 
Voltmeter, electrostatic, 31 

high resistance of, 54 

tests with, 53 
Voltmeters, 25 
Vulcanized india-rubber, tests of, 198 

Walmsley's rail bond tester, 521 
Ward Leonard turret-turning sys- 
tem, 737 
Water analyses, table of, 862 

calculations of horse-power, 939 

column equivalents, 929 

column, pressure per sq. inch, 929 

cubic feet discharged per minute, 
935 

expansion of, 858 

flow of, over weirs, 938 

flow of, through an orifice, 936 

flow of, in pipes, 869 

flowing in pipe, power of, 928 

for boiler feed, 858 

gas, 973 

heat units, per pound, 904 

horse-power of, cu. ft. table, 939 

horse-power of, miner's inch table, 
939 

mean specific heat of, 972 

table of pressure of, 931 

theoretical velocity and discharge, 
935 

tube boiler, 829 

weight above 212° F., 857 

weight of, condensed, 904 

weight per cubic foot, 856 

wheels, 940 
Waterfall, horse-power, 927 ^ 

Water-power, 926 

expense, yearly, 930 

property, report, synopsis, 926 
Water-tight door gear, United 

States Navy, 747 
Water wheels, impulse, 944 

Pelton impulse, 943 
Wattmeter price chart, 634 
Wattmeters, 615 

testing and calibrating of, 620 
Westinghouse integrating, 625 

reading of, 632 

connections of, 617 
W r ave form of current and E.M.F., 

705 
Wave-form meter, 706 
Weatherproof insulation, N. E. C., 
778 



INDEX. 



991 



Weaver speed recorder, 754 
Weber photometer, 391 
Weight of belts, 953 

of bricks, 824 

of coke, 853 

of hard drawn copper, 142 

of tarred hemp rope, 958 
Weights and measures, 961 

metrical equivalent, 963 

of cars, motors and trucks, 470 

of copper and brass wire and 
plates, 826 

of flat rolled iron, 797 

of iron, 796 

of motor trucks, 464 

of plate iron, 800 

of round bolt copper, '825 

of sheet and bar brass, 825 

of square and round bars, wrought 
iron. 799 
Weight of steel, 796 

and specific gravity of metals, 975 

of rails, 426 
Weir dam measurement, 937 

table, 938 
Weirs, Francis's formulae, 938 
Welding by electricity, 691 

rails, 694 
Westinghouse electromagnetic rail- 
way system, 537 
Wheatstone bridge, 28, 38 
White core wires and cables, 160-166 
Winches, deck, electrically opera- 
ted, 744 
Winding of armatures, 251 

of electro-magnets, 84 
Windings for rotary armatures, 291 

for rotaries, 291 
Wire rope, galvanized iron, 827 

rope, notes on uses of, 958 

rope, pliable hoisting, 828 

rope, transmission by means of, 
827 

ropes, horse-power, etc., of, 959 

table of A. I.E. E., 142-149 
Wire, galvanized iron, 154 

german silver, 180 

iron, data, 154-157 

manganine, 188 

nickeline, 187-191 



Wire, silicon bronze, 219 

span, dip of, 439 

span, data on, 440 

spans, table of deflection of, 209-218 

table, National Electrical Code, 769 

trolley, suspension of, 443 
Wires, capacity of, N.E.C., 769, 788 

general rules for, National Elec- 
trical Code, 771 

guard, 445 

lead covered, 166 

navy standard, 159 

or cables, faults in, 226 

paper insulated, 166 

resistance of, 42 

sag of , 205 

spaces occupied by (table), 91 
Wiring, bell, 137 

chart and table for alternating 
currents, 131 

for annunciators, 138 

for direct current, 127 

formulas, 130 

formula?, application of, for alter- 
nating current, 127 

formula?, general, 121 

gas-light, 139 

interior, National Electrical Code, 
768 

of cars, 475-480 

specifications for IT. S. Navy, 730 

specifications, N.E.C., 765 
Wood as a fuel, 854 

bulk, 853 

properties of, 818 

weight per cord, 854 
Wooden beams, safe load, 820 

stave pipe, 933 
Woods, comparative resistance of, 
219 

test of American, 819 

weights of various, 439 
Work and energy, units of, 12 
Wrought-iron columns, strength of, 

809 
Wright discount meter, 635 

Yachts, battery plants for, 571 

Zinc sulphate, resistance of, 676 



ADVERTISEMENTS. 



THE 



BRUSH 

ELECTRICAL ENGINEERING COMPANY, 

laimited. 



MANUFACTURERS OF 

STEAM ENGINES, DYNAMOS, 

ALTERNATORS, TRANSFORMERS 

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OF 

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Write for Lists to Head Offices : 

49 QUEEN VICTORIA ST., LONDON, E.C. 

[Folloxv matter. 



9 






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S ^ £ C> 8 M 




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for Imvie 

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301 Euston 

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elephone : 4226, 

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LIMITED. 

WARRINGTON. 

Telephone: 202. Telegrams: FILATURE. 



MANUFACTURERS OF 

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Telegraphic Address: FILATERR10. 



11 ADVERTISEMENTS. 

ASKHAM BROS. & WILSON, Ui 

SOLE MAKERS OF 

THE PATENT AUTOMATIC POINTS, 

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Adopted throughout the Country. 



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Prices and Illustrations on Application. 
We invite a visit to our Works — 



A DVERTISEMENTS. 



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ALLSOP, F. C. 

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Telephones : their Construction and Fitting. 6th Edition. 
3s. 6d. 

CROCKER, F. B. 

Electric Lighting. Vol. L, The Generating Plant. 12s. 6d. 
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FLEMING, J. A. 

Magnets and Electric Currents. 7s. 6d. 

HALLIDAY, G. 

ISotes on Design of Small Dynamo. 2nd Edition. 2s. 6d. 

HOSKICER, Colonel V. 

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KEMPE, H. R. 

A Handbook of Electri.al Testing. 6th Edition. 18s. 

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KENNELLY, A. E. 

Theoretical Elements of Electro-Dynamic Machinery. 
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LANGDON, W. E. 

The Application of Electricity to Railway Working. 
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LINTERN, W. 

The Motor Engineers' and Electrical Workers' Hand- 
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MAYCOCK, W. P. 

Practical Notes and Definitions. 2nd Edition. Cloth. 2s. 
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NORR1E, H. T. 

Induction Coils. 2nd Edition. 4s. 6d. net. 

SPRAGUE, J. S. 

Electricity: its Theory, Sources and Applications. 3rd 
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THOMPSON, S. P. 

Polyphase Electric Currents and Alternate Current 
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Dynamo-Electric Machinery. Seventh Edition in Pre- 
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Latest Dynamo-Electric Machines. An American Supple- 
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THOMPSON, S. P., and THOMAS, E. 



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15 



ADVEKTISEMENTS. 



CALLENDER'S 

Cable & Construction Co., Ltd, 

HAMILTON HOUSE, 
VICTORIA EMBANKMENT, E.C. 




1 



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16 




WORTHINGTON 

Pumping Engine Go*, 

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Codes used : A 1, ABC, and LIEBER'S. 



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17 



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THE 

EDISON & SWAN UNITED ELECTRIC CO. 

Limited. 

Head Office and Show Booms : 

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West End Depdt & Show Boom: 53 PARLIAMENT STREET, S.W. 

Manufacturers of the WORLD-RENOWNED 

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ALSO 
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Telegraphic Addresses: 
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Delivery from Stock on receipt of Telegram. 

ESTABLISHED 1868. 

W. T. GLOVER & CO., LTD. 

LONDON OFFICE: 

2 Queen Anne's Gate, Westminster. 
Works: Salford, Manchester. 

Contractors to B.M. Postmaster General, the Indian Government, the 
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Manufacturers of all Classes of 

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For General and Special Purposes. 

Sole Agent -^gggj^ REOSTENE 

NEW METAL, ^/j^Bf^B^BK^) the 

i Resistance of 



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^H^C ^Mj iK*t^UMwLj (Crompton's tw 

Sp®^^^^^^S^r^/Vy with Patent 

^XC^^ W^Zrv Solid Ku<is - a Rt - 

'■/S^S Jltea *C^* Improvement in 

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F or v^fc^S^Bl WR^Sf Compressed Bars 

all kinds of &X^M&tK£&mBr<tf (Crompton's twist) 

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GLOVER'S PATENT COVERED GUTTAPERCHA WIRE, 

For Leading-in, Tunnel, and Underground Wear. 

PATENT DIATRINE CABLES 

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E. S. HINDLEY 

Works: Bourton, Dorset. 

London Shoiv Booms and Store* : 
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STEAI^ENGINES. 




steam: boilers 



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'.-,- 



^U-END£^ 



N 



CABLE 



& 



CONSTRUCTION CO., Ltd. 



Head Office; 

Hamilton House, 
VICTORIA EMBANKMENT, E.C. 



Works : 

BELVEDERE, KENT. 




Laying: CaB lender Mains across 

LOWESTOFT HARBOUR. 



Face Title. 



LRBAo/8 






